Clinical Endocrinology (1990) 32, 363-372
THE EFFECT OF D- VERSUS L-PROPRANOLOL IN THE TREATMENT O F HYPERTHYROIDISM OTTO EBER, W O L F G A N G BUCHINGER, W O L F G A N G L I N D N E R , PETER LIND, M O N I K A RATH, G E R T KLIMA, W E R N E R LANGSTEGER A N D PETER K d L T R I N G E R Department of Internal Medicine, Barmherzige Briider Graz-Eggenberg Hospital and Institute of Pharmaceutical Chemistry, University of Graz, A-8010 Graz, Austria (Receiijed 19 May 1989; returnedfor revision 6 July I989:~?nallyrevised 14 July 1989, accepted 5 September 1989)
SUMMARY
The purpose of this study is to determine whether there is a difference in treatment of hyperthyroidism using either the D- or L-isomer of propranolol. Two groups of 20 patients with overt hyperthyroidism received either 120 mg Lor D-propranolol each for a period of 5 days. In the D-propranolol administered group there was a significant decrease in TT3 and fT3 plasma levels and in the ratio of TT3 to TT4; however, a significant increase occurred in rT3 values up to day 5. On the other hand, L-propranolol treatment resulted in a less pronounced decrease in TT4 and TT3 values, while all other thyroid hormone levels remained unchanged as, above all, did the T3/T4 ratio. The well known effect of D,L-propranolol upon peripheral conversion of T4 to T3 is thus not due to the beta-blocking action of ~-propranololbut is mainly conditioned by the Disomer which has no beta-blocking action itself. The effect of propranolol* on the peripheral thyroxine metabolism of hyperthroid patients has been described repeatedly (Nauman et al., 1974; Verhoeven et al., 1977; Wiersinger & Touber, 1977). The adjuvant administration of propranolol has become an established practice in the symptomatic treatment of hyperthyroidism (Wenzel, 1981; Utiger, 1984). It is true that other beta-blockers, non-selective but also beta-2-selective, improve the clinical symptoms (Murchinson et al., 1976,1979, McDevitt &Nelson, 1978; Nilsson et al,, 1979, 1980; How et al., 1980; Jones et al., 1980) by inhibiting the betareceptors that are more prevalent in the heart (Ciaraldi & Marinetti, 1977; Williams & Lefkowitz, 1977; Krawietz, 1988) yet without exerting a direct influence on the peripheral hormone metabolism. Correspondence: Professor Otto Eber, Internal Department, Barmherzige Briider Eggenberg Hospital, Bergstrasse 27, A-8020 Graz-Eggenberg, Austria.
* Propranolol is a synthetic drug containing a chiral carbon atom (see formula scheme Fig. 1). The betablocking property of this drug (usually administered as the racemic 1 : 1mixture of D- and ~-propranolol)is to be ascribed to ~-propranolol,whereas ~-propranololis devoid of beta-blocking activity at the dose employed (Rahn et al., 1974; Rahn, 1983).
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0.Eber et al.
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I
I I I I
L-Propranolol
I
@ /
D-Propranolol
Mirror image
Fig. 1. Formula scheme of the optical isomers of propranolol (‘asymmetric carbon atom).
Heyma et al. (1980b) were able to prove a significant decrease in triiodothyronine and in the ratio of T3 to T4, while the T4 values remained practically unchanged with Dpropranolol in hypothyroid and euthyroid patients. Up to now, the effect of the laevo-rotating isomer, L-propranolol, on the T4 to T3 conversion has been investigated neither in euthyroid nor in hyperthyroid subjects, nor has the effect of D-propranolol on hyperthyroid patients been studied. The study, based on 40 hyperthyroid patients, served to determine whether the influence on the peripheral conversion is to be ascribed non-specifically to both optical isomers or probably only to one isomer. PATIENTS AND METHODS Patient selection The study was ethically approved by our religious order and was restricted to in-patients suffering from hyperthyroidism, who had been subjected to thorough examination. Hospitalization of the patients was necessary because of a local government decree, according to which radioiodine therapy can be performed only on in-patients. The diagnosis of hyperthyroidism was carefully verified both clinically and by laboratory tests (suppressed basal TSH and suppressed TRH-test, elevated TT3, f T3 and fT4). The group comprised 40 patients, four male and 36 female, aged between 22 and 72 years, mean age 46.4 years. None of the patients had undergone treatment with betablockers in the past 6 weeks and the use of beta-blockers was not contra-indicated in any of the subjects (Landsberg & Young, 1987). Patients who had received antithyroid drugs during the 3 months prior to the study or who showed iodine-induced hyperthyroidism (urinary iodine excretion > 250 pg/g creatinine) or protein-binding anomalies were excluded from the study.
D - us L-propranolol in hyperthyroidism
365
After informed consent to participate the patients were randomly divided into two groups: (A) D-propranolol group: n = 20 (2m, 18f), age range 24-72, mean: 48.3 and (B) Lpropranolol group: n = 20 (2m,18f), age range 22-67, mean: 44.5. Group A was treated with 120 mg D-propranolol, group B with 120 mg L-propranolol per day. The doses were administered orally in single doses of 40 mg at 0600, 1400 and 2200 h. The first blood samples were obtained before treatment and then daily 2.5 h after the first drug intake. Resting pulse was measured daily before the first drug intake. Basal metabolic rate (BMR) was determined in the morning before breakfast under conditions of rest prior to and on the 5th day of treatment, using the Siemens’ Metabolostat. During D- or L-propranolol treatment no antithyroid drugs were given to exclude interactions; from day 5 onwards-i.e. after end of propranolol isomer administration-therapy with methimazole(MMI) was commenced in accordance with a well established scheme.
Materials
At the Institute of Pharmaceutical Chemistry, University of Graz, both D- and Lpropranolol with an optical purity (0.p.) >99% were obtained from D, L-propranolol (USP-21 quality supplied by Schweizerhall, Switzerland) according to a method developed by Lindner et al. (1984; US Patent 4,652,672;03-24, 1987). The dosage forms (hard gelatine capsules consisting of 40 mg D- and L-propranolol respectively, 130 mg alpha-mannitol and 2 g carbosil) were produced and controlled according to European Pharmacopeia standard in the same institute. All chemicals used for the synthetic work as well as for the HPLC analyses (stereospecific drug monitoring) were analytical grade from Merck (FRG) and Fluka (Switzerland), respectively.
In-vitro analysis and propranolol drug monitoring
Prior to the beginning of the study and during the daily controls total T3 (TT3; normal range: 0.80-2.46 nmol/I; CV 1.6%), free T3 (fT3; normal range: 3.60-8.60 pmol/l; CV 5.3%), reverse T3 (rT3; normal range: 0*15-054 nmol/l; CV 6.2%), total T4 (TT4; normal range: 47.9-148 nmol/l; CV 6.2%), free T4 (fT4; normal range: 7.7-23.2 pmol/l; CV 6.5%), sex hormone binding globulin (SHBG normal range: 30-90 nmol/l; CV 9.2%) and high sensitivity TSH (normal range: 0.4-3.5 mU/1; CV 6.2%) levels were determined with commercially available kits. In all patients, the serum levels of propranolol isomers were measured daily. According to a protocol described by Lindner ef al. (1984), 1 ml plasma samplewas diluted with 1 ml 0.5 M phosphate buffer (pH 9.8), doped with an internal standard (D, L-tert.buty1 propranolol) and extracted with ether in an Extrelut Column (Merck). To the dried organic layer the chiral derivatizing reagent DATAAN (D,D-O,O-diacetyl tartaric acid anhydride, 0.p. > 99.9%) and trichloroacetic acid were added. After reaction (14 h, 40°C) the ether was evaporated by nitrogen and the residue redissolved in 100 pl water/ methanol/acetic acid (60/20/20)of which 50 pl were injected into HPLC system. (Column: 125 x 4 mm i.d., Lichrosorb ODs, 5 pm; mobile phase: 0.1 M NH, acetate/acetonitrile (60/ 40), pH 4.6; fluorescence detection: ~ ~ 2 nm, 8 0 ~ ~ 3 nm). 3 5
0.Eber et al.
366
.,
Fig. 2. Serum concentrations of TT3 during treatment with D- or 0,L-propranolol (means+SEM). In the analysis of covariance there is a significant difference between D- and L-propranolol ( P i 0.05).
Statistical analysis
An analysis of covariance with the respective basal value as covariant was carried out in order to demonstrate differencesin results both in control and in treatment course; not only the treatment factor but also the interaction, i.e. treatment x time, corrected according to Greenhouse and Geisser (1959) and Freund et al. (1986) were computed. An analysis of variance per treatment group was also computed in order to show general differences that may arise during the processing of each group. The basal value was used as the starting point in the time element. The results are given as means$ SEM. RESULTS Thyroid hormones and peripheral thyroid parameters Group A
In the group treated with D-propranolol, TT3 decreased significantly (Pc 0-0001) by 2 1.3% on day 5 as shown in Fig. 2. The f T3-level (Fig. 3) was reduced by 17.4% on day 4 and by 14.3% on day 5 (P< 0.0005). The rT3-level as depicted in Fig. 4 rose significantly up to day 5 by 42.9% (P
THE EFFECT OF D- VERSUS L-PROPRANOLOL IN THE TREATMENT O F HYPERTHYROIDISM OTTO EBER, W O L F G A N G BUCHINGER, W O L F G A N G L I N D N E R , PETER LIND, M O N I K A RATH, G E R T KLIMA, W E R N E R LANGSTEGER A N D PETER K d L T R I N G E R Department of Internal Medicine, Barmherzige Briider Graz-Eggenberg Hospital and Institute of Pharmaceutical Chemistry, University of Graz, A-8010 Graz, Austria (Receiijed 19 May 1989; returnedfor revision 6 July I989:~?nallyrevised 14 July 1989, accepted 5 September 1989)
SUMMARY
The purpose of this study is to determine whether there is a difference in treatment of hyperthyroidism using either the D- or L-isomer of propranolol. Two groups of 20 patients with overt hyperthyroidism received either 120 mg Lor D-propranolol each for a period of 5 days. In the D-propranolol administered group there was a significant decrease in TT3 and fT3 plasma levels and in the ratio of TT3 to TT4; however, a significant increase occurred in rT3 values up to day 5. On the other hand, L-propranolol treatment resulted in a less pronounced decrease in TT4 and TT3 values, while all other thyroid hormone levels remained unchanged as, above all, did the T3/T4 ratio. The well known effect of D,L-propranolol upon peripheral conversion of T4 to T3 is thus not due to the beta-blocking action of ~-propranololbut is mainly conditioned by the Disomer which has no beta-blocking action itself. The effect of propranolol* on the peripheral thyroxine metabolism of hyperthroid patients has been described repeatedly (Nauman et al., 1974; Verhoeven et al., 1977; Wiersinger & Touber, 1977). The adjuvant administration of propranolol has become an established practice in the symptomatic treatment of hyperthyroidism (Wenzel, 1981; Utiger, 1984). It is true that other beta-blockers, non-selective but also beta-2-selective, improve the clinical symptoms (Murchinson et al., 1976,1979, McDevitt &Nelson, 1978; Nilsson et al,, 1979, 1980; How et al., 1980; Jones et al., 1980) by inhibiting the betareceptors that are more prevalent in the heart (Ciaraldi & Marinetti, 1977; Williams & Lefkowitz, 1977; Krawietz, 1988) yet without exerting a direct influence on the peripheral hormone metabolism. Correspondence: Professor Otto Eber, Internal Department, Barmherzige Briider Eggenberg Hospital, Bergstrasse 27, A-8020 Graz-Eggenberg, Austria.
* Propranolol is a synthetic drug containing a chiral carbon atom (see formula scheme Fig. 1). The betablocking property of this drug (usually administered as the racemic 1 : 1mixture of D- and ~-propranolol)is to be ascribed to ~-propranolol,whereas ~-propranololis devoid of beta-blocking activity at the dose employed (Rahn et al., 1974; Rahn, 1983).
363
0.Eber et al.
364
I
I I I I
L-Propranolol
I
@ /
D-Propranolol
Mirror image
Fig. 1. Formula scheme of the optical isomers of propranolol (‘asymmetric carbon atom).
Heyma et al. (1980b) were able to prove a significant decrease in triiodothyronine and in the ratio of T3 to T4, while the T4 values remained practically unchanged with Dpropranolol in hypothyroid and euthyroid patients. Up to now, the effect of the laevo-rotating isomer, L-propranolol, on the T4 to T3 conversion has been investigated neither in euthyroid nor in hyperthyroid subjects, nor has the effect of D-propranolol on hyperthyroid patients been studied. The study, based on 40 hyperthyroid patients, served to determine whether the influence on the peripheral conversion is to be ascribed non-specifically to both optical isomers or probably only to one isomer. PATIENTS AND METHODS Patient selection The study was ethically approved by our religious order and was restricted to in-patients suffering from hyperthyroidism, who had been subjected to thorough examination. Hospitalization of the patients was necessary because of a local government decree, according to which radioiodine therapy can be performed only on in-patients. The diagnosis of hyperthyroidism was carefully verified both clinically and by laboratory tests (suppressed basal TSH and suppressed TRH-test, elevated TT3, f T3 and fT4). The group comprised 40 patients, four male and 36 female, aged between 22 and 72 years, mean age 46.4 years. None of the patients had undergone treatment with betablockers in the past 6 weeks and the use of beta-blockers was not contra-indicated in any of the subjects (Landsberg & Young, 1987). Patients who had received antithyroid drugs during the 3 months prior to the study or who showed iodine-induced hyperthyroidism (urinary iodine excretion > 250 pg/g creatinine) or protein-binding anomalies were excluded from the study.
D - us L-propranolol in hyperthyroidism
365
After informed consent to participate the patients were randomly divided into two groups: (A) D-propranolol group: n = 20 (2m, 18f), age range 24-72, mean: 48.3 and (B) Lpropranolol group: n = 20 (2m,18f), age range 22-67, mean: 44.5. Group A was treated with 120 mg D-propranolol, group B with 120 mg L-propranolol per day. The doses were administered orally in single doses of 40 mg at 0600, 1400 and 2200 h. The first blood samples were obtained before treatment and then daily 2.5 h after the first drug intake. Resting pulse was measured daily before the first drug intake. Basal metabolic rate (BMR) was determined in the morning before breakfast under conditions of rest prior to and on the 5th day of treatment, using the Siemens’ Metabolostat. During D- or L-propranolol treatment no antithyroid drugs were given to exclude interactions; from day 5 onwards-i.e. after end of propranolol isomer administration-therapy with methimazole(MMI) was commenced in accordance with a well established scheme.
Materials
At the Institute of Pharmaceutical Chemistry, University of Graz, both D- and Lpropranolol with an optical purity (0.p.) >99% were obtained from D, L-propranolol (USP-21 quality supplied by Schweizerhall, Switzerland) according to a method developed by Lindner et al. (1984; US Patent 4,652,672;03-24, 1987). The dosage forms (hard gelatine capsules consisting of 40 mg D- and L-propranolol respectively, 130 mg alpha-mannitol and 2 g carbosil) were produced and controlled according to European Pharmacopeia standard in the same institute. All chemicals used for the synthetic work as well as for the HPLC analyses (stereospecific drug monitoring) were analytical grade from Merck (FRG) and Fluka (Switzerland), respectively.
In-vitro analysis and propranolol drug monitoring
Prior to the beginning of the study and during the daily controls total T3 (TT3; normal range: 0.80-2.46 nmol/I; CV 1.6%), free T3 (fT3; normal range: 3.60-8.60 pmol/l; CV 5.3%), reverse T3 (rT3; normal range: 0*15-054 nmol/l; CV 6.2%), total T4 (TT4; normal range: 47.9-148 nmol/l; CV 6.2%), free T4 (fT4; normal range: 7.7-23.2 pmol/l; CV 6.5%), sex hormone binding globulin (SHBG normal range: 30-90 nmol/l; CV 9.2%) and high sensitivity TSH (normal range: 0.4-3.5 mU/1; CV 6.2%) levels were determined with commercially available kits. In all patients, the serum levels of propranolol isomers were measured daily. According to a protocol described by Lindner ef al. (1984), 1 ml plasma samplewas diluted with 1 ml 0.5 M phosphate buffer (pH 9.8), doped with an internal standard (D, L-tert.buty1 propranolol) and extracted with ether in an Extrelut Column (Merck). To the dried organic layer the chiral derivatizing reagent DATAAN (D,D-O,O-diacetyl tartaric acid anhydride, 0.p. > 99.9%) and trichloroacetic acid were added. After reaction (14 h, 40°C) the ether was evaporated by nitrogen and the residue redissolved in 100 pl water/ methanol/acetic acid (60/20/20)of which 50 pl were injected into HPLC system. (Column: 125 x 4 mm i.d., Lichrosorb ODs, 5 pm; mobile phase: 0.1 M NH, acetate/acetonitrile (60/ 40), pH 4.6; fluorescence detection: ~ ~ 2 nm, 8 0 ~ ~ 3 nm). 3 5
0.Eber et al.
366
.,
Fig. 2. Serum concentrations of TT3 during treatment with D- or 0,L-propranolol (means+SEM). In the analysis of covariance there is a significant difference between D- and L-propranolol ( P i 0.05).
Statistical analysis
An analysis of covariance with the respective basal value as covariant was carried out in order to demonstrate differencesin results both in control and in treatment course; not only the treatment factor but also the interaction, i.e. treatment x time, corrected according to Greenhouse and Geisser (1959) and Freund et al. (1986) were computed. An analysis of variance per treatment group was also computed in order to show general differences that may arise during the processing of each group. The basal value was used as the starting point in the time element. The results are given as means$ SEM. RESULTS Thyroid hormones and peripheral thyroid parameters Group A
In the group treated with D-propranolol, TT3 decreased significantly (Pc 0-0001) by 2 1.3% on day 5 as shown in Fig. 2. The f T3-level (Fig. 3) was reduced by 17.4% on day 4 and by 14.3% on day 5 (P< 0.0005). The rT3-level as depicted in Fig. 4 rose significantly up to day 5 by 42.9% (P
