CONTRACEPTION
COMPARAJIVE CROSS-OVER PHARMACOKINETIC STUDY ON TWO TYPES OF POSTCOITAL CONTRACEPTWE TABLETS CONTAINING LEVONORGESTREL He Chang-hail, Shi Yong-en’, Liao Ding-ling’, Zhu Yue-hua’ Xu &an-qiu’, S.A. Matlir?, P.M. Vince2, K. Fotherby3 and P.F.A. Van Look4
‘Shanghai Institute of Planned Parenthood Research, Shanghai, People’s Republic of China, 2Chemistry Department, City University, London, UK, 3Royal Postgraduate Medical School, London, UK, 4Special Programme of Research, Development and Research Reproduction, World Health Organization, Geneva, Switzerland.
Training
in Human
ABSTRACT
A pharmaceutical and pharmacokinetic study was carried out on levonorgestrel tablets from two different sources (Hungarian- and Chinese-made). Both preparations contained 0.75 mg levonorgestrel and had been shown to have similar contraceptive efficacy and side effects when used for postcoital contraception. Absorption and bioavailability of the Hungarian-made tablets were greater as evidenced by higher serum concentrations of levonorgestrel, a greater area under the concentration-time curve during the first 24 hours, and a more marked suppressive effect on SHBG levels. These differences most probably reflect differences in their pharmaceutical formulation, in particular the extent of tablet dissolution and the degree of micronisation of levonorgestrel.
Address for correspondence: Dr P.F.A. Van Look, Special Programme of Research, Developmentand ResearchTraining in Human Reproduction, World Health Organization, 1211 Geneva 27, Switzerland Submitted Accepted
for publication for publication
MAY 1990 VOL. 41 NO. 5
January Feburary
15, 1990 5, 1990
CONTRACEPTION INTRODUCTION Levonorgestrel administered orally in doses of 0.4-0.75 mg has been shown to be an effective postcoital contraceptive (1,2,3). In a multicentre trial conducted by the World Health Organization (4) the observed failure rate per treated cycle for a 0.75 mg dose was 0.8%, a value similar to that reported for other hormonal approaches to emergency postcoital contraception (5 and 6 for reviews). More recently, postcoital administration of levonorgestrel as a possiblealternative to the “visiting” or “vacation” pills in use in the People’s Republic of China has been investigated (7). In this randomized, double-blind, multicentre trial, two types of 0.75 mg levonorgestrel tablets were compared: PostinorR (Gedeon Richter Ltd., Hungary) which is registered for postcoital contraception in several countries, and a comparable levonorgestrel pill produced in the People’s Republic of China (Beijing No. 3 Pharmaceutical Factory, Beijing). Both preparations were shown to have a similar method failure rate of 1.1% per treated cycle. The present paper describes the pharmaceutical and pharmacokinetic characteristics of these two types of tablets. SUBJECTS
AND METHODS
Permission for the study had been given by the Ethics Committees of the Shanghai Institute for Planned Parenthood Research and of the World Health Organization, and informed consent was obtained from the volunteers. Ten normal, healthyfemalevolunteers wererandomlydivided intotwo groups. All the subjects had regular menstrual cycles (25-35 days) and had not used any steroidal agents nor lactated for at least three months prior to admission. No other drugs were taken during the course of the study. A medicat history was taken from each subject beforeentering thestudyand afull medical andgynaecotogical examination performed. Normal liver and kidney functions were confirmed by routine laboratory tests. Both the Hungarian-made and Chinese-made tablets contained 0.75 mg levonorgestrel and were from the same batch as those used in the clinical efficacy study (7). Women in Group I took one tablet of PostinorR on day 3 of the treatment cycle and one Chinese-made tablet on day 7 of the same cycle. For women in Group II, the order of drug administration was reversed. From each woman, a blood sample was obtained from an antecubital vein immediately before and at 1, 2, 4, 8, 12 and 24 h after taking the tablets. Blood samples were allowed to clot at room temperature for at least 30 mins and then centrifuged. The separated serum was stored at -20°C until analysed for levonorgestrel content by radioimmunoassay (8). SHBG was measured by a previously described method (9) in the samples collected just prior to and at 24 h after tablet intake.
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION The levonorgestrel content of the tablets was determined by extracting separate tablets with ethanol:water (9:l by vol.) and centrifuging the resulting solution. Aliquots of the solution were analysed on reverse phase HPLC [column of 3km HypersiCODS (8 cm x 0.4 cm i.d.) eluted with acetonitrile:water (6:4 by vol.)] and monitored at 241 nm. The particle size of the levonorgestrel powder used in formulating the tablets was determined using a Malvern 2600/3600 Particle Sizer (Malvern Instruments Ltd., UK). Tablet dissolution rates were determined by adding single tablets to 900 ml distilled water or 0.1 N hydrocholoric acid, maintained at 37°C and stirred at an identical constant rate. Samples (1 ml) were withdrawn from each dissolution flask at timed intervals for analysis of levonorgestrel content by HPLC. Three tablets from each source were studied at each pH. The pharmacokinetic analysis of the levonorgestrel datawas performed on the basis of a two-compartment open model using a CTPP-I programme and an iterative method of curve fitting. RESULTS 1. Pharmacokinetic data Mean (&SD) values for the physical characteristics of the women enrolled in the study were: age, 27.453.7 y; height, 161.3~4.3 cm; weight, 53.8k5.9 kg; body mass index, 21.1 ~2.8. Values for serum levonorgestrel values are plotted in Fig. 1,
concentrations are shown in Table I and the mean
14,
al
I
1
12
I
4
Q lime
Fig. 1.
Serum
formulations
levonorgestrel
each containing
concentrations
MAY 1990 VOL. 41 NO. 5
i
24
after dosing (h)
(means
0.75 mg levonorgestrel
I
12
and
SD) after
oral administration
of two different
CONTRACEPTION Table I. Serum lcvonorgestrel concentrations oral administration
(nghnl) after
of two formulations of 0.75 mg Ievonorgestrel
Time (h) after dosing
Subject 1
2
4
8
12
24
Postinor’ 1
11.44
15.60
9.60
8.70
5.20
2.08
2
11.28
12.00
7.52
4.80
3.72
2.40
3
7.20
6.24
3.52
3.12
2.60
1.68
4
7.04
8.76
4.64
2.28
1.68
1.04
5
1.20
6.96
3.20
2.52
2.24
0.88
6
6.80
8.04
3.20
2.52
1.72
1.08
7
13.76
12.96
11.20
6.90
4.00
2.08 0.80
8
6.24
9.36
6.80
2.52
2.48
9
6.16
9.36
8.32
3.78
2.72
1.80
10
8.80
7.44
6.80
4.50
3.60
2.28
Mean
7.99
9.67
6.48
4.16
3.00
1.61
SD
3.53
2.97
2.80
2.15
1.11
0.61
Chinese pill
1
5.20
6.00
7.84
6.66
3.72
0.84
2
5.76
7.56
5.68
2.88
2.68
1.64
3
5.60
6.60
4.86
4.22
3.96
1.60
4
1.52
3.00
2.80
1.80
1.12
0.80
5
3.36
4.80
3.76
3.30
2.96
1.76
6
1.76
3.00
2.00
1.56
1 A0
0.60
7
5.28
6.72
3.20
2.70
2.40
1.68
8
4.16
5.04
3.30
1.84
1.28
1.08
9
3.20
4.08
4.80
2.40
2.12
0.88
10
1.36
3.84
6.48
4.44
2.80
1.52
Mean
3.72
5.06
4.47
3.18
2.44
1.24
SD
1.74
1.61
1.81
1.57
0.98
0.44
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION Absorption was rapid in most subjects and maximum serum concentrations of levonorgestrel were achieved in less than 2 h in seven women after PostinoP but in only three after the Chinese pill. Serum concentrations in all subjects except one at 2 h, and in all except two at 24 h, were higher when taking PostinoF and, consequently, mean serum concentrations at all times were higher after PostinoF than after the Chinese pill. In both groups at all times from 2 to 24 h, there was a 2- to 4-fold between-subject variation in the levonorgestrel concentrations.
Table II. F’b-cokinetbz
parameters for a single oral dose of hvo formulations of 0.75mg
levonorgestrel in tan subjects (for abbreviations sea Results) Parameter
PosthoP mean
Chinese pill
SD
range
mean
SD
range
ka (h-l)
0.84
0.23
0.56-1.24
0.59’
0.21
0.24-0.93
l-a 0)
0.88
0.23
0.55-1.23
1.3s*
0.69
0.74-2.92
11.2
3.4
8.1-18.4
5.9’
1.7
3.4-8.2
1.9
0.6
1.O-2.7
3.1’
1.2
2.1-5.3
a (h-V
0.65
0.30
0.31-1.21
0.44
0.22
0.17-0.89
P W)
0.056
0.017
0.038-0.086
0.056
0.029
0.029-0.065
Ta 01)
1.28
0.56
0.57-2.20
2.00
1.06
0.78-4.00
Cmax (@ml) Tm=
Q
TB 01)
13.3
3.7
8.0-18.2
14.8
6.0
5.4-24.0
Cl o/h)
6.1
1.9
3.8-9.4
8.4
3.6
5.7-18.1
Vd (1)
115
41
44-163
174
83
48-290
K,, 01-v
0.33
0.23
0.10-0.82
0.18
0.11
0.03-0.30
K,, 0.0
0.20
0.09
0.10-0.33
0.21
0.15
0.11-0.59
K,, W)
0.17
0.03
0.12-0.22
0.11’
0.02
0.08-0.13
*“Co.,
92.2
34.3
54.@152
64.4’
21.9
33.1-99.1
124.0
42.8
66.8-176.6
92.3
28.8
42.7-121.8
(oghnuh) AUC_ (nghnvh)
l
denotes statistically significant difference between PostinoF and the Chinese pill
MAY 19SOVOL. 41 NO. 5
551
CONTRACEPTION As expected, the pharmacokinetic parameters (Table II) derived from the levonorgestrel concentrations showed marked differences between the two groups. The rate constant for absorption (ka) was lower after administration of the Chinese pill and, consequently, the half-life of absorption (Ta) and the time to reach peak serum concentrations (Tmax) were longer. Due to these factors the distribution rate constant (a) was lower and the half-life of distribution (To) longer after the Chinese pill. The elimination rate constant (8) and the half-life of elimination (Tp) were similar after both formulations, which is to be expected. This finding and the fact that the peak serum concentration(Cmax)wasloweraftertheChinesepillsuggestthatsomeofthedosewas not absorbed when the Chinese pill was given. This is confirmed by the finding that the area under the serum concentration-time curve (AUC), both for O-24 h and O-a0 were lower by about 28% after the Chinese pill. There were no statistically significant differences between the two formulations in respect of clearance (Cl), apparent volume of distribution (Vd) or the transfer constants between central and peripheral compartments (K,, and K,,). However K,, (rate constant for elimination from central compartment via excretion) was significantly smaller for the Chinese pill indicating slower elimination as a result of the slower absorption. 2. Serum SHBG
concentrations
Table III. Serum SHBG concentrations
(nmol/I) after oral administration
of 0.75 mg levonorgestrel
(subjects 1,2,3,7 and 8 received the Chinese pill 0x1day 3 and Postinors on day 7; subjects 4,5,6,9 and 10 received the pills in the reverse order)
Subject
2
51.7
48.5
42.7
36.7
62.2
58.2
48.2
44.4
3
54.6
49.5
43.7
38.1
4
49.2
41.0
27.3
23.3
5
42.2
37.9
34.7
28.2
6
36.4
27.8
23.2
20.5
7
49.2
47.3
44.2
36.9
8
29.6
28.0
20.0
17.1
9
68.1
66.9
59.4
50.2
10
64.0
60.4
53.4
47.7
46.6 12.3
11.6
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION Values for serum SHBG concentrations are shown in Table III. There was no difference in the pretreatment levels of SHBG between the five subjects assigned to PostinoPfirst (52.0&.13.7 nmol/l)and thoseassigned to thechinese pill first (49.5Ll2.1 nmol/l). Irrespective of which formulation was taken first, there was a progressive decrease in the concentration during the study period in each subject. Based on mean values, by 24h after the first dose on day 3. SHBG levels had decreased by 8.1% and by the time of the next dose on day 7, levels were 21.7% lower than on day 3. Administration of the second dose provoked a further 13.6% decrease. For subjects taking the Chinese pill first, the mean (&SD) per cent decrease by day 4 was 6.3~2.0% whereas for those taking PostinorR first the per cent decrease was 11.6 f 8.7%. Percentage decreases after the second dose of levonorgestrel were slightly greater, 14.2 f 3.2% for the Chinese pill and 13.2 f 3.2% for PostinoP. 3. Pharmaceutical analysis Both batches of tablets conformed to USP requirements in terms of levonorgestrel content. The average content of the Chinese tablets was 97% (range 90%-l 05%) and that of PostinorR 101% (range 96%-l 07%). There was, however, a major difference in the particle size of the levonorgestrel used in their manufacture. PostinoP was made with levonorgestrel powder which had 73% of particles below 23 pm and 17% above 100 Frn, whereas the Chinese tablets were made with levonorgestrel powder which had only 10% below 23 pm and 71 X above 100 pm. The dissolution rates of the tablets were measured in distilled water at pH 7 and in 0.1 N hydrochloric acid (pH 1) to mimic the acidic conditions of the stomach. The results are shown in Fig. 2. PostinorR tablets dissolved more rapidly at pH 1 than at pH 7, releasing 679 pg after 5 h at pH 1 and 546 p,g at pH 7. By 24 h under both conditions the total amount of levonorgestrel had been released (747 j.tg at pH 1,765 pg at pH 7). The Chinese tablets dissolved only slightly more rapidly at pH 1 than at pH 7 and the release of levonorgestrel was not only much slower but also incomplete. After 5 h, only 315 pg had been released at pH 1 and 269 kg at pH 7. The total amount released after 24 h was 466 t.tg at pH 1 and 413 pg at pH 7.
DISCUSSION Despite the fact that in the clinical trial no significant differences were observed between the two levonorgestrel formulations in terms of contraceptive efficacy, cycle control and side effects (7), the present results demonstrate a marked difference between them in their pharmacokinetics. The differences relate mainly to the absorption serum levonorgestrel concentrations up to 4 h after administration were phase; significantly higher after PostinorR than after the Chinese pill. Absorption of the Chinese pill was also slower than that of PostinoP. These differences led to a lower bioavailability from O-24 h for the Chinese pill as shown by the significant difference in the AUC. Although the total bioavailability (AUCa was not statistically significantly different due
MAY 1990 VOL. 41 NO. 5
563
CONTRACEPTION
Fig. 2. Jhsolotbn
ratea of Postinor” and Chinese tableta containing 0.75 sq levonorgestrel In acidic and
neutral medin. Values are means f SD.
to the wide between-subject variability, the mean value for PostinoP was 34% greater than the mean value for the Chinese pill suggesting that much of the levonorgestrel in the latter formulation was not absorbed at later times after administration. The serum levonorgestrel concentrations found in the present study agree with those reported previously (10). The pharmacokinetic differences between the two preparations would appear to result from differences in their pharmaceutical formulation. PostinoP contained levonorgestrel which was more homogeneous in particle size than that in the Chinese pill and the mean particle size was much smaller. Partiile size is one of the factors affecting the dissolution rate of the formulation and hence the rate and extent of absorption of the active ingredient. In vitro dissolution rate measurements showed Postino? to breakdown and release levonorgestrel at a faster rate than the Chinese pill. It has been demonstrated for a number of drugs that reduction in the partiile size (micronisation) of the drug in a pharmaceutical formulation may lead to higher blood levels than those obtained with the same dose of drug of larger particle size (11, 12). The mechanism of the effect is not always clear but for drugs with a poor solubility in aqueous media, and this may include the steroids, micronisation may lead to an increased dissolution rate of the drug formulation and thereby enhance its absorption. For the steroids, the earliest report appears to be that of Gibian eta/. (13) who showed that micronisation not only increased the dissolution rate of norethisterone acetate but also increased its biological activity. Micronised norethisterone acetate was four times more potent than the non-micronised form in the ovulation inhibition bioassay in rats. More recently (cf. 14) it has been demonstrated that, by micronisation. therapeutically effective levels of progesterone can be achieved by oral administration. Our findings are in agreement with these reports.
564
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION The dissolution rate experiments clearly showed marked differences between the two tablet formulations. PostinoP broke down rapidly, releasing almost all its content of levonorgestrel within 6 h, whereas the Chinese tablet broke down much more slowly, less than 50% of the levonorgestrel being released in 6 h and little further was released in the next 16 h. Even when the determinations with the Chinese tabtets were continued for 46 h, only minor additional amounts of levonorgestrel were released during the extra incubation time. The remainder of the levonorgestrel which was not released could be obtained by extracting tablet residues, recovered from the dissolution studies, with ethanol. Evidently, the Chinese tablets failed to release their levonorgestrel either at pH 1 or pH 7 and about half of the steroid content remained associated with the insoluble excipients in a form which limited its solubility in water but not in ethanol. Differences between PostinorR and the Chinese pill in the magnitude of the levonorgestrel concentrations attained in the first 6 h after administration were reflected in changes in serum SHBG concentration. By 24 h after administration of the first dose of PostinoP, serum SHBG decreased by 11.6% compared to the significantly lower decrease (6.3%) after the first dose of the Chinese pill. Likewise, by 4 days after administration (day 7) the mean decrease was greater for PostinoP (25.6%) than for the Chinese pill (20.5%). Thus, by 4 days after administration of a single dose of levonorgestrel, SHBG levels were still suppressed and administration of the second dose provoked a further decrease of 13-14%. The slowness of serum SHBG levels to return to pretreatment levels is in accordance with previous findings (11) that even after administration of much lower doses of levonorgestrel, SHBG did not return to pretreatment levels until at least eight days after discontinuation of the drug. The present investigation clearly demonstrates the necessity for performing comparative pharmacokinetic studies when two or more formulations containing the same dose of active drug are used in clinical trials. Differences in the pharmaceutical formulation of the two tablets led to major differences in their pharmacokinetics and this may entail differences in their clinical effects. However, the latter did not occur with the two formulations studied (7). Two factors may explain this. Firstly. single doses of levonorgestrel were given at 4-day intervals in the pharmacokinetic study whereas the clinical study involved multiple doses. Secondly, the pharmacokinetic differences between the twoformulations related mainly to the absorption phase whereas differences in the concentrations during the elimination phase (period from 4 to 24 h after administration), which may be the important time period in respect of clinical efficacy, were much smaller. If the level of serum levonorgestrel during the elimination phase is more important for the clinical effect than that during theearlier period after administration, the present findings suggest that it may be possible to reduce the dose of levonorgestrel without decreasing efficacy by modifying the pharmaceutical formulation so as to further flatten the pharmacokinetic profile.
MAY 1990 VOL. 41 NO. 5
505
CONTRACEPTION
ACKNOWLEDGEMENTS This investigation was supported financially by WHO’s Special Programme of Research, Development and ResearchTraining in Human Reproduction. PostinorR was Hungary and the Chinese kindly supplied by Gedeon Richter Ltd., Budapest, levonorgestrel tablets by Beijing No. 3 Pharmaceutical Factory, Beijing, People’s Republic of China. REFERENCES 1. Kesserii E, Larrailaga A. Parada Contraception 1973; 7: 367-79.
J.
Postcoital
contraception
with D-norgestrel
2. Craft 1,Foss GL, Warren RJ, Fotherby K. Effect of norgestrel administered on pituitary ovarian function. Contraception 1975; 12: 589-98. 3. Seregely
G. Results of a multicentre
trial of Postinor.
intermittently
Ther Hung 1982; 30: 72-8.
4. WHO Task Force on Post-ovulatory Methods for Fertility Regulation. Postcoital contraception with levonorgestrel during the peri-ovulatory phase of the menstrual cycle. Contraception 1987; 36: 275-86. 5. Van Look PFA. Postcoital contraception: acover-upstory. In: Diczfalusy E, Bygdeman M. eds. Fertilty regulation today and tomorrow. New York: Raven Press, 1987: 29-42. 6. Fasoli overview
M, Parazzini of published
F, Cecchetti G, La Vecchia C. Post-coital contraception: studies. Contraception 1989; 39: 459-468 and 699-700.
an
7. He Chang-hai, Shi Yong-en, Xu Jian-qiu, Van Look PFA. A multicentre clinical study of two types of fevonorgestrel tablets administered for postcoital contraception. international Journal of Gynecology and Obstetrics (submitted). 8. Warren RJ, Fotherby K. Radioimmunoassayof synthetic progestogens, and norgestrel. J Endocrinol1974; 62: 605-l 8.
norethisterone
9. Rosner W. A simplified method for the quantitative determination of testosteroneestradioi-binding globulin activity in human plasma. J C/in EndocrinolMetab 1972; 34: 983-8. IO. Shi Yong-en, Zheng Shu-heng, Zhu Yue-hua, He Chang-hai, K. Pharmacokinetic study of levonorgestrel used as a postcoital 1988; 37: 359-69.
Yu Pei-ping, Fotherby agent. Contraception
11. Song Si, Chen Jun-kang, He Mei-Ii, Fotherby K. Effect of some oral contraceptives on serum concentrations of sex hormone binding globulin and ceruloplasmin. Contraception 1989; 39: 385-99.
MAY
1990 VOL. 41. NO. 5
CONTRACEPTION
12. Lachman L. Lieberman HA, Kanig JL. The theory pharmacy. 2nd ed. Philadelphia: Lea and Fabiger, 1976.
and practice
of industrial
13. Gibian H, Kopp R, Kramer M. Neumann F, Richter H. Effect of particle size on biological activity of norethisterone acetate. Acta fhysiol Lat Amer 1968; 18: 323-6. 14. Sitruk-Ware R, Bricaire C, de Lignieres B, Yaneva H, Mauvais-Jarvis micronized progesterone. Contraception 1987; 36: 373-402.
MAY
1990 VOL. 41 NO. 5
P.
Oral
567
COMPARAJIVE CROSS-OVER PHARMACOKINETIC STUDY ON TWO TYPES OF POSTCOITAL CONTRACEPTWE TABLETS CONTAINING LEVONORGESTREL He Chang-hail, Shi Yong-en’, Liao Ding-ling’, Zhu Yue-hua’ Xu &an-qiu’, S.A. Matlir?, P.M. Vince2, K. Fotherby3 and P.F.A. Van Look4
‘Shanghai Institute of Planned Parenthood Research, Shanghai, People’s Republic of China, 2Chemistry Department, City University, London, UK, 3Royal Postgraduate Medical School, London, UK, 4Special Programme of Research, Development and Research Reproduction, World Health Organization, Geneva, Switzerland.
Training
in Human
ABSTRACT
A pharmaceutical and pharmacokinetic study was carried out on levonorgestrel tablets from two different sources (Hungarian- and Chinese-made). Both preparations contained 0.75 mg levonorgestrel and had been shown to have similar contraceptive efficacy and side effects when used for postcoital contraception. Absorption and bioavailability of the Hungarian-made tablets were greater as evidenced by higher serum concentrations of levonorgestrel, a greater area under the concentration-time curve during the first 24 hours, and a more marked suppressive effect on SHBG levels. These differences most probably reflect differences in their pharmaceutical formulation, in particular the extent of tablet dissolution and the degree of micronisation of levonorgestrel.
Address for correspondence: Dr P.F.A. Van Look, Special Programme of Research, Developmentand ResearchTraining in Human Reproduction, World Health Organization, 1211 Geneva 27, Switzerland Submitted Accepted
for publication for publication
MAY 1990 VOL. 41 NO. 5
January Feburary
15, 1990 5, 1990
CONTRACEPTION INTRODUCTION Levonorgestrel administered orally in doses of 0.4-0.75 mg has been shown to be an effective postcoital contraceptive (1,2,3). In a multicentre trial conducted by the World Health Organization (4) the observed failure rate per treated cycle for a 0.75 mg dose was 0.8%, a value similar to that reported for other hormonal approaches to emergency postcoital contraception (5 and 6 for reviews). More recently, postcoital administration of levonorgestrel as a possiblealternative to the “visiting” or “vacation” pills in use in the People’s Republic of China has been investigated (7). In this randomized, double-blind, multicentre trial, two types of 0.75 mg levonorgestrel tablets were compared: PostinorR (Gedeon Richter Ltd., Hungary) which is registered for postcoital contraception in several countries, and a comparable levonorgestrel pill produced in the People’s Republic of China (Beijing No. 3 Pharmaceutical Factory, Beijing). Both preparations were shown to have a similar method failure rate of 1.1% per treated cycle. The present paper describes the pharmaceutical and pharmacokinetic characteristics of these two types of tablets. SUBJECTS
AND METHODS
Permission for the study had been given by the Ethics Committees of the Shanghai Institute for Planned Parenthood Research and of the World Health Organization, and informed consent was obtained from the volunteers. Ten normal, healthyfemalevolunteers wererandomlydivided intotwo groups. All the subjects had regular menstrual cycles (25-35 days) and had not used any steroidal agents nor lactated for at least three months prior to admission. No other drugs were taken during the course of the study. A medicat history was taken from each subject beforeentering thestudyand afull medical andgynaecotogical examination performed. Normal liver and kidney functions were confirmed by routine laboratory tests. Both the Hungarian-made and Chinese-made tablets contained 0.75 mg levonorgestrel and were from the same batch as those used in the clinical efficacy study (7). Women in Group I took one tablet of PostinorR on day 3 of the treatment cycle and one Chinese-made tablet on day 7 of the same cycle. For women in Group II, the order of drug administration was reversed. From each woman, a blood sample was obtained from an antecubital vein immediately before and at 1, 2, 4, 8, 12 and 24 h after taking the tablets. Blood samples were allowed to clot at room temperature for at least 30 mins and then centrifuged. The separated serum was stored at -20°C until analysed for levonorgestrel content by radioimmunoassay (8). SHBG was measured by a previously described method (9) in the samples collected just prior to and at 24 h after tablet intake.
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION The levonorgestrel content of the tablets was determined by extracting separate tablets with ethanol:water (9:l by vol.) and centrifuging the resulting solution. Aliquots of the solution were analysed on reverse phase HPLC [column of 3km HypersiCODS (8 cm x 0.4 cm i.d.) eluted with acetonitrile:water (6:4 by vol.)] and monitored at 241 nm. The particle size of the levonorgestrel powder used in formulating the tablets was determined using a Malvern 2600/3600 Particle Sizer (Malvern Instruments Ltd., UK). Tablet dissolution rates were determined by adding single tablets to 900 ml distilled water or 0.1 N hydrocholoric acid, maintained at 37°C and stirred at an identical constant rate. Samples (1 ml) were withdrawn from each dissolution flask at timed intervals for analysis of levonorgestrel content by HPLC. Three tablets from each source were studied at each pH. The pharmacokinetic analysis of the levonorgestrel datawas performed on the basis of a two-compartment open model using a CTPP-I programme and an iterative method of curve fitting. RESULTS 1. Pharmacokinetic data Mean (&SD) values for the physical characteristics of the women enrolled in the study were: age, 27.453.7 y; height, 161.3~4.3 cm; weight, 53.8k5.9 kg; body mass index, 21.1 ~2.8. Values for serum levonorgestrel values are plotted in Fig. 1,
concentrations are shown in Table I and the mean
14,
al
I
1
12
I
4
Q lime
Fig. 1.
Serum
formulations
levonorgestrel
each containing
concentrations
MAY 1990 VOL. 41 NO. 5
i
24
after dosing (h)
(means
0.75 mg levonorgestrel
I
12
and
SD) after
oral administration
of two different
CONTRACEPTION Table I. Serum lcvonorgestrel concentrations oral administration
(nghnl) after
of two formulations of 0.75 mg Ievonorgestrel
Time (h) after dosing
Subject 1
2
4
8
12
24
Postinor’ 1
11.44
15.60
9.60
8.70
5.20
2.08
2
11.28
12.00
7.52
4.80
3.72
2.40
3
7.20
6.24
3.52
3.12
2.60
1.68
4
7.04
8.76
4.64
2.28
1.68
1.04
5
1.20
6.96
3.20
2.52
2.24
0.88
6
6.80
8.04
3.20
2.52
1.72
1.08
7
13.76
12.96
11.20
6.90
4.00
2.08 0.80
8
6.24
9.36
6.80
2.52
2.48
9
6.16
9.36
8.32
3.78
2.72
1.80
10
8.80
7.44
6.80
4.50
3.60
2.28
Mean
7.99
9.67
6.48
4.16
3.00
1.61
SD
3.53
2.97
2.80
2.15
1.11
0.61
Chinese pill
1
5.20
6.00
7.84
6.66
3.72
0.84
2
5.76
7.56
5.68
2.88
2.68
1.64
3
5.60
6.60
4.86
4.22
3.96
1.60
4
1.52
3.00
2.80
1.80
1.12
0.80
5
3.36
4.80
3.76
3.30
2.96
1.76
6
1.76
3.00
2.00
1.56
1 A0
0.60
7
5.28
6.72
3.20
2.70
2.40
1.68
8
4.16
5.04
3.30
1.84
1.28
1.08
9
3.20
4.08
4.80
2.40
2.12
0.88
10
1.36
3.84
6.48
4.44
2.80
1.52
Mean
3.72
5.06
4.47
3.18
2.44
1.24
SD
1.74
1.61
1.81
1.57
0.98
0.44
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION Absorption was rapid in most subjects and maximum serum concentrations of levonorgestrel were achieved in less than 2 h in seven women after PostinoP but in only three after the Chinese pill. Serum concentrations in all subjects except one at 2 h, and in all except two at 24 h, were higher when taking PostinoF and, consequently, mean serum concentrations at all times were higher after PostinoF than after the Chinese pill. In both groups at all times from 2 to 24 h, there was a 2- to 4-fold between-subject variation in the levonorgestrel concentrations.
Table II. F’b-cokinetbz
parameters for a single oral dose of hvo formulations of 0.75mg
levonorgestrel in tan subjects (for abbreviations sea Results) Parameter
PosthoP mean
Chinese pill
SD
range
mean
SD
range
ka (h-l)
0.84
0.23
0.56-1.24
0.59’
0.21
0.24-0.93
l-a 0)
0.88
0.23
0.55-1.23
1.3s*
0.69
0.74-2.92
11.2
3.4
8.1-18.4
5.9’
1.7
3.4-8.2
1.9
0.6
1.O-2.7
3.1’
1.2
2.1-5.3
a (h-V
0.65
0.30
0.31-1.21
0.44
0.22
0.17-0.89
P W)
0.056
0.017
0.038-0.086
0.056
0.029
0.029-0.065
Ta 01)
1.28
0.56
0.57-2.20
2.00
1.06
0.78-4.00
Cmax (@ml) Tm=
Q
TB 01)
13.3
3.7
8.0-18.2
14.8
6.0
5.4-24.0
Cl o/h)
6.1
1.9
3.8-9.4
8.4
3.6
5.7-18.1
Vd (1)
115
41
44-163
174
83
48-290
K,, 01-v
0.33
0.23
0.10-0.82
0.18
0.11
0.03-0.30
K,, 0.0
0.20
0.09
0.10-0.33
0.21
0.15
0.11-0.59
K,, W)
0.17
0.03
0.12-0.22
0.11’
0.02
0.08-0.13
*“Co.,
92.2
34.3
54.@152
64.4’
21.9
33.1-99.1
124.0
42.8
66.8-176.6
92.3
28.8
42.7-121.8
(oghnuh) AUC_ (nghnvh)
l
denotes statistically significant difference between PostinoF and the Chinese pill
MAY 19SOVOL. 41 NO. 5
551
CONTRACEPTION As expected, the pharmacokinetic parameters (Table II) derived from the levonorgestrel concentrations showed marked differences between the two groups. The rate constant for absorption (ka) was lower after administration of the Chinese pill and, consequently, the half-life of absorption (Ta) and the time to reach peak serum concentrations (Tmax) were longer. Due to these factors the distribution rate constant (a) was lower and the half-life of distribution (To) longer after the Chinese pill. The elimination rate constant (8) and the half-life of elimination (Tp) were similar after both formulations, which is to be expected. This finding and the fact that the peak serum concentration(Cmax)wasloweraftertheChinesepillsuggestthatsomeofthedosewas not absorbed when the Chinese pill was given. This is confirmed by the finding that the area under the serum concentration-time curve (AUC), both for O-24 h and O-a0 were lower by about 28% after the Chinese pill. There were no statistically significant differences between the two formulations in respect of clearance (Cl), apparent volume of distribution (Vd) or the transfer constants between central and peripheral compartments (K,, and K,,). However K,, (rate constant for elimination from central compartment via excretion) was significantly smaller for the Chinese pill indicating slower elimination as a result of the slower absorption. 2. Serum SHBG
concentrations
Table III. Serum SHBG concentrations
(nmol/I) after oral administration
of 0.75 mg levonorgestrel
(subjects 1,2,3,7 and 8 received the Chinese pill 0x1day 3 and Postinors on day 7; subjects 4,5,6,9 and 10 received the pills in the reverse order)
Subject
2
51.7
48.5
42.7
36.7
62.2
58.2
48.2
44.4
3
54.6
49.5
43.7
38.1
4
49.2
41.0
27.3
23.3
5
42.2
37.9
34.7
28.2
6
36.4
27.8
23.2
20.5
7
49.2
47.3
44.2
36.9
8
29.6
28.0
20.0
17.1
9
68.1
66.9
59.4
50.2
10
64.0
60.4
53.4
47.7
46.6 12.3
11.6
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION Values for serum SHBG concentrations are shown in Table III. There was no difference in the pretreatment levels of SHBG between the five subjects assigned to PostinoPfirst (52.0&.13.7 nmol/l)and thoseassigned to thechinese pill first (49.5Ll2.1 nmol/l). Irrespective of which formulation was taken first, there was a progressive decrease in the concentration during the study period in each subject. Based on mean values, by 24h after the first dose on day 3. SHBG levels had decreased by 8.1% and by the time of the next dose on day 7, levels were 21.7% lower than on day 3. Administration of the second dose provoked a further 13.6% decrease. For subjects taking the Chinese pill first, the mean (&SD) per cent decrease by day 4 was 6.3~2.0% whereas for those taking PostinorR first the per cent decrease was 11.6 f 8.7%. Percentage decreases after the second dose of levonorgestrel were slightly greater, 14.2 f 3.2% for the Chinese pill and 13.2 f 3.2% for PostinoP. 3. Pharmaceutical analysis Both batches of tablets conformed to USP requirements in terms of levonorgestrel content. The average content of the Chinese tablets was 97% (range 90%-l 05%) and that of PostinorR 101% (range 96%-l 07%). There was, however, a major difference in the particle size of the levonorgestrel used in their manufacture. PostinoP was made with levonorgestrel powder which had 73% of particles below 23 pm and 17% above 100 Frn, whereas the Chinese tablets were made with levonorgestrel powder which had only 10% below 23 pm and 71 X above 100 pm. The dissolution rates of the tablets were measured in distilled water at pH 7 and in 0.1 N hydrochloric acid (pH 1) to mimic the acidic conditions of the stomach. The results are shown in Fig. 2. PostinorR tablets dissolved more rapidly at pH 1 than at pH 7, releasing 679 pg after 5 h at pH 1 and 546 p,g at pH 7. By 24 h under both conditions the total amount of levonorgestrel had been released (747 j.tg at pH 1,765 pg at pH 7). The Chinese tablets dissolved only slightly more rapidly at pH 1 than at pH 7 and the release of levonorgestrel was not only much slower but also incomplete. After 5 h, only 315 pg had been released at pH 1 and 269 kg at pH 7. The total amount released after 24 h was 466 t.tg at pH 1 and 413 pg at pH 7.
DISCUSSION Despite the fact that in the clinical trial no significant differences were observed between the two levonorgestrel formulations in terms of contraceptive efficacy, cycle control and side effects (7), the present results demonstrate a marked difference between them in their pharmacokinetics. The differences relate mainly to the absorption serum levonorgestrel concentrations up to 4 h after administration were phase; significantly higher after PostinorR than after the Chinese pill. Absorption of the Chinese pill was also slower than that of PostinoP. These differences led to a lower bioavailability from O-24 h for the Chinese pill as shown by the significant difference in the AUC. Although the total bioavailability (AUCa was not statistically significantly different due
MAY 1990 VOL. 41 NO. 5
563
CONTRACEPTION
Fig. 2. Jhsolotbn
ratea of Postinor” and Chinese tableta containing 0.75 sq levonorgestrel In acidic and
neutral medin. Values are means f SD.
to the wide between-subject variability, the mean value for PostinoP was 34% greater than the mean value for the Chinese pill suggesting that much of the levonorgestrel in the latter formulation was not absorbed at later times after administration. The serum levonorgestrel concentrations found in the present study agree with those reported previously (10). The pharmacokinetic differences between the two preparations would appear to result from differences in their pharmaceutical formulation. PostinoP contained levonorgestrel which was more homogeneous in particle size than that in the Chinese pill and the mean particle size was much smaller. Partiile size is one of the factors affecting the dissolution rate of the formulation and hence the rate and extent of absorption of the active ingredient. In vitro dissolution rate measurements showed Postino? to breakdown and release levonorgestrel at a faster rate than the Chinese pill. It has been demonstrated for a number of drugs that reduction in the partiile size (micronisation) of the drug in a pharmaceutical formulation may lead to higher blood levels than those obtained with the same dose of drug of larger particle size (11, 12). The mechanism of the effect is not always clear but for drugs with a poor solubility in aqueous media, and this may include the steroids, micronisation may lead to an increased dissolution rate of the drug formulation and thereby enhance its absorption. For the steroids, the earliest report appears to be that of Gibian eta/. (13) who showed that micronisation not only increased the dissolution rate of norethisterone acetate but also increased its biological activity. Micronised norethisterone acetate was four times more potent than the non-micronised form in the ovulation inhibition bioassay in rats. More recently (cf. 14) it has been demonstrated that, by micronisation. therapeutically effective levels of progesterone can be achieved by oral administration. Our findings are in agreement with these reports.
564
MAY 1990 VOL. 41. NO. 5
CONTRACEPTION The dissolution rate experiments clearly showed marked differences between the two tablet formulations. PostinoP broke down rapidly, releasing almost all its content of levonorgestrel within 6 h, whereas the Chinese tablet broke down much more slowly, less than 50% of the levonorgestrel being released in 6 h and little further was released in the next 16 h. Even when the determinations with the Chinese tabtets were continued for 46 h, only minor additional amounts of levonorgestrel were released during the extra incubation time. The remainder of the levonorgestrel which was not released could be obtained by extracting tablet residues, recovered from the dissolution studies, with ethanol. Evidently, the Chinese tablets failed to release their levonorgestrel either at pH 1 or pH 7 and about half of the steroid content remained associated with the insoluble excipients in a form which limited its solubility in water but not in ethanol. Differences between PostinorR and the Chinese pill in the magnitude of the levonorgestrel concentrations attained in the first 6 h after administration were reflected in changes in serum SHBG concentration. By 24 h after administration of the first dose of PostinoP, serum SHBG decreased by 11.6% compared to the significantly lower decrease (6.3%) after the first dose of the Chinese pill. Likewise, by 4 days after administration (day 7) the mean decrease was greater for PostinoP (25.6%) than for the Chinese pill (20.5%). Thus, by 4 days after administration of a single dose of levonorgestrel, SHBG levels were still suppressed and administration of the second dose provoked a further decrease of 13-14%. The slowness of serum SHBG levels to return to pretreatment levels is in accordance with previous findings (11) that even after administration of much lower doses of levonorgestrel, SHBG did not return to pretreatment levels until at least eight days after discontinuation of the drug. The present investigation clearly demonstrates the necessity for performing comparative pharmacokinetic studies when two or more formulations containing the same dose of active drug are used in clinical trials. Differences in the pharmaceutical formulation of the two tablets led to major differences in their pharmacokinetics and this may entail differences in their clinical effects. However, the latter did not occur with the two formulations studied (7). Two factors may explain this. Firstly. single doses of levonorgestrel were given at 4-day intervals in the pharmacokinetic study whereas the clinical study involved multiple doses. Secondly, the pharmacokinetic differences between the twoformulations related mainly to the absorption phase whereas differences in the concentrations during the elimination phase (period from 4 to 24 h after administration), which may be the important time period in respect of clinical efficacy, were much smaller. If the level of serum levonorgestrel during the elimination phase is more important for the clinical effect than that during theearlier period after administration, the present findings suggest that it may be possible to reduce the dose of levonorgestrel without decreasing efficacy by modifying the pharmaceutical formulation so as to further flatten the pharmacokinetic profile.
MAY 1990 VOL. 41 NO. 5
505
CONTRACEPTION
ACKNOWLEDGEMENTS This investigation was supported financially by WHO’s Special Programme of Research, Development and ResearchTraining in Human Reproduction. PostinorR was Hungary and the Chinese kindly supplied by Gedeon Richter Ltd., Budapest, levonorgestrel tablets by Beijing No. 3 Pharmaceutical Factory, Beijing, People’s Republic of China. REFERENCES 1. Kesserii E, Larrailaga A. Parada Contraception 1973; 7: 367-79.
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Postcoital
contraception
with D-norgestrel
2. Craft 1,Foss GL, Warren RJ, Fotherby K. Effect of norgestrel administered on pituitary ovarian function. Contraception 1975; 12: 589-98. 3. Seregely
G. Results of a multicentre
trial of Postinor.
intermittently
Ther Hung 1982; 30: 72-8.
4. WHO Task Force on Post-ovulatory Methods for Fertility Regulation. Postcoital contraception with levonorgestrel during the peri-ovulatory phase of the menstrual cycle. Contraception 1987; 36: 275-86. 5. Van Look PFA. Postcoital contraception: acover-upstory. In: Diczfalusy E, Bygdeman M. eds. Fertilty regulation today and tomorrow. New York: Raven Press, 1987: 29-42. 6. Fasoli overview
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an
7. He Chang-hai, Shi Yong-en, Xu Jian-qiu, Van Look PFA. A multicentre clinical study of two types of fevonorgestrel tablets administered for postcoital contraception. international Journal of Gynecology and Obstetrics (submitted). 8. Warren RJ, Fotherby K. Radioimmunoassayof synthetic progestogens, and norgestrel. J Endocrinol1974; 62: 605-l 8.
norethisterone
9. Rosner W. A simplified method for the quantitative determination of testosteroneestradioi-binding globulin activity in human plasma. J C/in EndocrinolMetab 1972; 34: 983-8. IO. Shi Yong-en, Zheng Shu-heng, Zhu Yue-hua, He Chang-hai, K. Pharmacokinetic study of levonorgestrel used as a postcoital 1988; 37: 359-69.
Yu Pei-ping, Fotherby agent. Contraception
11. Song Si, Chen Jun-kang, He Mei-Ii, Fotherby K. Effect of some oral contraceptives on serum concentrations of sex hormone binding globulin and ceruloplasmin. Contraception 1989; 39: 385-99.
MAY
1990 VOL. 41. NO. 5
CONTRACEPTION
12. Lachman L. Lieberman HA, Kanig JL. The theory pharmacy. 2nd ed. Philadelphia: Lea and Fabiger, 1976.
and practice
of industrial
13. Gibian H, Kopp R, Kramer M. Neumann F, Richter H. Effect of particle size on biological activity of norethisterone acetate. Acta fhysiol Lat Amer 1968; 18: 323-6. 14. Sitruk-Ware R, Bricaire C, de Lignieres B, Yaneva H, Mauvais-Jarvis micronized progesterone. Contraception 1987; 36: 373-402.
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1990 VOL. 41 NO. 5
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