Br.J. Anaesth. (1978), 50, 885
EFFECTS OF AGE AND SEX ON KETAMINE ANAESTHESIA IN THE RAT A. E. WATERMAN AND A. LIVINGSTON SUMMARY
Intraperitoneal injections of ketamine 75 mg kg"1 in rats of both sexes (age 1-16 weeks) revealed a significant relationship between increased age and decreased duration of sleeping time for both sexes during the first 3 weeks of age. This decrease in sleeping time seemed to be associated with the increased production of the cyclohexanone oxidation metabolite of ketamine. After 3 weeks of age there was a greater sleeping time in the female rat than the male and this seemed to be associated with a greater ability of the male to produce the cyclohexanone oxidation metabolite.
METHODS
Albino Wistar rats from a cross-fostered inbred colony fed on standard diet and water ad libitum were housed under constant conditions of temperature and light. Groups of six male or female rats aged 1, 2, 3, 4, 6, 12 and 16 weeks old were studied. Each animal was injected i.p. with ketamine hydrochloride A. E. WATERMAN, B.V.SC, D.V.A., PH.D., M.RX.V.S.J A. LIVINGSTON, B.SC, B.VET.MED., PH.D., M.RX.V.S.; Depart-
ment of Pharmacology, Medical School, University of Bristol, University Walk, Bristol BS8 1TD. 0007-0912/78/0050-0885 $01.00
75 mg kg" 1 using either a 5-mg ml" 1 or 10-mg ml" 1 dilution of the commercially available 100 mg ml" 1 solution (Ketalar, Parke Davis & Co. Ltd). The time to loss of the righting reflex (onset time) and the duration of the loss (sleeping time) was noted. At the point of recovery of the righting reflex the rats were killed by decapitation and a sample of mixed venous and arterial blood was collected in a heparinized tube. The blood was centrifuged at 1000^ for 15 min and the plasma was deep frozen until assay. The concentrations of ketamine and its two principal metabolites, the demethylated product (metabolite I) and the subsequent oxidation product (metabolite II), were assayed by a method based on the gas-liquid chromatographic method of Chang and Glazko (1972). The assays were performed against known standards of the three compounds using 2-amino-2-(o-bromophenyl)-2-methylamino cyclohexanone as an internal standard. The samples were extracted with benzene and derivatives of ketamine and its metabolites were made with heptofluorobutyric anhydride and pyridine. Samples of 1 fxlitre, dried over anhydrous sodium sulphate, were injected onto a column of 3 % OV-17 on Gas Chrome Q at a temperature of 195 °C on a Pye Unicam 104 Gasliquid chromatograph equipped with a nickel-63 electron capture ionization detector. The only aspect of the assay procedure which differed from that of Chang and Glazko (1972) was that nitrogen 45 ml min" 1 was used as the carrier gas instead of methane/ argon, which resulted in slightly longer retention times. RESULTS
The onset time of a single injection of ketamine 75 mgkg" 1 i.p. in male rats increased while sleeping © Macmillan Journals Ltd 1978
Downloaded from http://bja.oxfordjournals.org/ at Monash University on June 22, 2015
Ketamine is used widely for anaesthesia in children (Roberts, 1967) particularly for the dressing of burns (Roberts, 1967; Corssen and Oget, 1971) and for radiotherapy (Cronin et al., 1972; Bennett and Bullimore, 1973). Ketamine is metabolized in the liver (Chang, Dill and Glazko, 1965) and it has been recognized for a long time that young animals and humans may be more sensitive to drugs which rely on liver metabolism for the termination of their effects (Founts and Adamson, 1959; Hahn and Skala, 1971). Sexual status can be an important factor also in determining the effect of certain drugs, particularly barbiturates (Kato and Gillette, 1965) and it has been noted that female patients seem to experience more psychotomimetic effects after ketamine anaesthesia than do males (Knox et al., 1970; Bovill et al.,1971). We have investigated the actions of ketamine in rats of both sexes and of various ages to determine the influences of age and sex on the actions and metabolism of this drug. A preliminary report of some of these studies has been published (Livingston and Waterman, 1977).
886
BRITISH JOURNAL OF ANAESTHESIA
time decreased with increasing age (fig. 1). Two of the 1-week-old rats died during the period of anaesthesia and the mean value for sleeping time in this group of animals is taken from four animals. Onset time was significantly shorter in the 1-week age group compared with the others, increasing markedly to 8 weeks of age and thereafter decreasing gradually, but the onset times at 8, 12 and 16 weeks were not significantly different from each other.
, sleeping time
100-0
—-o onset time
900 900 "c 700
>-500
o I too
20™
3 '•si
UJ
I 300
inI
. , sleeping time o— -o onset time
1000
eoo
UJ Ul
05
12
700
o 51
10
100
600
30 U]
500
"I
6
8 12 AGE (weeks)
16
FIG. 2. The duration of action of ketamine 75 mg kg- 1 i.p. in female rats of various ages, showing onset time O O and sleeping time • • . Mean + SEM of six animals except 1-week group (five).
m
400
20
3
5
300
15
200
to
100
05
12
8
12 AGE (weeks)
~"
16
FIG. 1. The duration of action of ketamine 75 mgkg- 1 i.p. in male rats of various ages, showing onset time O O and sleeping time • • . Mean±SEM of six animals except 1-week group (four).
The sleeping times decreased rapidly with age up to 4 weeks of age and thereafter there was little change. The differences from the 1-week age group were significant from 3 weeks onwards, but after 4 weeks none of the sleeping times was significantly different from the others. Following a single dose of ketamine 75 mg kg- 1 i.p. in female rats (fig. 2), the pattern of changes in both onset and sleeping time was similar to that in male rats. Only one of the youngest age group died under anaesthesia. The pattern of significant differences was similar to that found in the male rats. Comparison of the male and female data for onset time showed no particular pattern (fig. 3) and there was no significant difference overall in the sexes. Comparison of the values for sleeping times revealed that at nearly all ages the sleeping time was longer in the females (fig. 4). Analysis of variance showed that there was a significant difference between sexes
Downloaded from http://bja.oxfordjournals.org/ at Monash University on June 22, 2015
900
200
4
6 AGE (weeks)
FIG. 3. Comparison of the time to lose the righting reflex by male and female rats of various ages after ketamine 75 mg kg" 1 i.p. **• Significant difference between sexes of same age (P< 0.001) using Student's t test.
(P< 0.001) if the rats aged 3-16 weeks were considered. There was no such significant difference in the 1- and 2-week-old rats. The concentrations of ketamine and metabolite I in male rats at the point of recovery decreased with increasing age. Metabolite II did not appear in the plasma until 3 weeks of age and then increased steadily to plateau at about 6 weeks of age, by which time ketamine and metabolite I concentrations had decreased significantly from the 1-week values (fig. 5). In the female rats plasma concentrations followed a pattern similar to those of the male rats, but the
AGE AND SEX IN KETAMINE ANAESTHESIA IN RATS •—• Ketamine o—o Metabolite I ...... Metabolite II
5.0-
D
e 4.0 %
Males Females
•I 3.0H 2
1 2.03
16
6 AGE (weeks)
Ketamine Metabolite I Metabolite II
4.0-
3 o 3.0-
2.0o
S i.oa. 2
4
6
8 10 12 Age (weeks)
14
4
--fU
6
8
10
12
i
14 16
Age (weeks)
FIG. 4. Comparison of sleeping times of male and female rats of different ages following ketamine 75 mg kg" 1 i.p. * Significant difference between sexes of same age (P< 0.05) using Student's t test. •^
•§
16
FIG. 5. Concentration of ketamine and its metabolites found in the plasma of male rats at recovery after ketamine 75 mg kg" 1 i.p. Mean±SEM of six animals except for 1-week group (four).
ketamine concentrations were not significantly less until 8 weeks of age, whilst the metabolite I concentrations were significantly less by 3 weeks of age (fig. 6). Again, metabolite II was not detected in 1and 2-week-old rats, appearing first in the plasma of 3-week-old rats. Concentrations increased to a maximum at 4 weeks and remained unchanged thereafter (fig. 6). Comparison of the plasma concentrations of the drug and its metabolites in both sexes at recovery showed some interesting differences. Ketamine concentrations were consistently greater in the
FIG. 6. Concentration of ketamine and its metabolites found in the plasma of female rats at recovery after ketamine 75 mg kg" 1 i.p. Mean + SEM of six animals except for 1-week group (five).
females, but there was no significant overall difference with age. The concentrations of metabolite I were, in general, greater in the female rats at most age groups; analysis of variance indicated that there was a significant difference between the sexes (P
EFFECTS OF AGE AND SEX ON KETAMINE ANAESTHESIA IN THE RAT A. E. WATERMAN AND A. LIVINGSTON SUMMARY
Intraperitoneal injections of ketamine 75 mg kg"1 in rats of both sexes (age 1-16 weeks) revealed a significant relationship between increased age and decreased duration of sleeping time for both sexes during the first 3 weeks of age. This decrease in sleeping time seemed to be associated with the increased production of the cyclohexanone oxidation metabolite of ketamine. After 3 weeks of age there was a greater sleeping time in the female rat than the male and this seemed to be associated with a greater ability of the male to produce the cyclohexanone oxidation metabolite.
METHODS
Albino Wistar rats from a cross-fostered inbred colony fed on standard diet and water ad libitum were housed under constant conditions of temperature and light. Groups of six male or female rats aged 1, 2, 3, 4, 6, 12 and 16 weeks old were studied. Each animal was injected i.p. with ketamine hydrochloride A. E. WATERMAN, B.V.SC, D.V.A., PH.D., M.RX.V.S.J A. LIVINGSTON, B.SC, B.VET.MED., PH.D., M.RX.V.S.; Depart-
ment of Pharmacology, Medical School, University of Bristol, University Walk, Bristol BS8 1TD. 0007-0912/78/0050-0885 $01.00
75 mg kg" 1 using either a 5-mg ml" 1 or 10-mg ml" 1 dilution of the commercially available 100 mg ml" 1 solution (Ketalar, Parke Davis & Co. Ltd). The time to loss of the righting reflex (onset time) and the duration of the loss (sleeping time) was noted. At the point of recovery of the righting reflex the rats were killed by decapitation and a sample of mixed venous and arterial blood was collected in a heparinized tube. The blood was centrifuged at 1000^ for 15 min and the plasma was deep frozen until assay. The concentrations of ketamine and its two principal metabolites, the demethylated product (metabolite I) and the subsequent oxidation product (metabolite II), were assayed by a method based on the gas-liquid chromatographic method of Chang and Glazko (1972). The assays were performed against known standards of the three compounds using 2-amino-2-(o-bromophenyl)-2-methylamino cyclohexanone as an internal standard. The samples were extracted with benzene and derivatives of ketamine and its metabolites were made with heptofluorobutyric anhydride and pyridine. Samples of 1 fxlitre, dried over anhydrous sodium sulphate, were injected onto a column of 3 % OV-17 on Gas Chrome Q at a temperature of 195 °C on a Pye Unicam 104 Gasliquid chromatograph equipped with a nickel-63 electron capture ionization detector. The only aspect of the assay procedure which differed from that of Chang and Glazko (1972) was that nitrogen 45 ml min" 1 was used as the carrier gas instead of methane/ argon, which resulted in slightly longer retention times. RESULTS
The onset time of a single injection of ketamine 75 mgkg" 1 i.p. in male rats increased while sleeping © Macmillan Journals Ltd 1978
Downloaded from http://bja.oxfordjournals.org/ at Monash University on June 22, 2015
Ketamine is used widely for anaesthesia in children (Roberts, 1967) particularly for the dressing of burns (Roberts, 1967; Corssen and Oget, 1971) and for radiotherapy (Cronin et al., 1972; Bennett and Bullimore, 1973). Ketamine is metabolized in the liver (Chang, Dill and Glazko, 1965) and it has been recognized for a long time that young animals and humans may be more sensitive to drugs which rely on liver metabolism for the termination of their effects (Founts and Adamson, 1959; Hahn and Skala, 1971). Sexual status can be an important factor also in determining the effect of certain drugs, particularly barbiturates (Kato and Gillette, 1965) and it has been noted that female patients seem to experience more psychotomimetic effects after ketamine anaesthesia than do males (Knox et al., 1970; Bovill et al.,1971). We have investigated the actions of ketamine in rats of both sexes and of various ages to determine the influences of age and sex on the actions and metabolism of this drug. A preliminary report of some of these studies has been published (Livingston and Waterman, 1977).
886
BRITISH JOURNAL OF ANAESTHESIA
time decreased with increasing age (fig. 1). Two of the 1-week-old rats died during the period of anaesthesia and the mean value for sleeping time in this group of animals is taken from four animals. Onset time was significantly shorter in the 1-week age group compared with the others, increasing markedly to 8 weeks of age and thereafter decreasing gradually, but the onset times at 8, 12 and 16 weeks were not significantly different from each other.
, sleeping time
100-0
—-o onset time
900 900 "c 700
>-500
o I too
20™
3 '•si
UJ
I 300
inI
. , sleeping time o— -o onset time
1000
eoo
UJ Ul
05
12
700
o 51
10
100
600
30 U]
500
"I
6
8 12 AGE (weeks)
16
FIG. 2. The duration of action of ketamine 75 mg kg- 1 i.p. in female rats of various ages, showing onset time O O and sleeping time • • . Mean + SEM of six animals except 1-week group (five).
m
400
20
3
5
300
15
200
to
100
05
12
8
12 AGE (weeks)
~"
16
FIG. 1. The duration of action of ketamine 75 mgkg- 1 i.p. in male rats of various ages, showing onset time O O and sleeping time • • . Mean±SEM of six animals except 1-week group (four).
The sleeping times decreased rapidly with age up to 4 weeks of age and thereafter there was little change. The differences from the 1-week age group were significant from 3 weeks onwards, but after 4 weeks none of the sleeping times was significantly different from the others. Following a single dose of ketamine 75 mg kg- 1 i.p. in female rats (fig. 2), the pattern of changes in both onset and sleeping time was similar to that in male rats. Only one of the youngest age group died under anaesthesia. The pattern of significant differences was similar to that found in the male rats. Comparison of the male and female data for onset time showed no particular pattern (fig. 3) and there was no significant difference overall in the sexes. Comparison of the values for sleeping times revealed that at nearly all ages the sleeping time was longer in the females (fig. 4). Analysis of variance showed that there was a significant difference between sexes
Downloaded from http://bja.oxfordjournals.org/ at Monash University on June 22, 2015
900
200
4
6 AGE (weeks)
FIG. 3. Comparison of the time to lose the righting reflex by male and female rats of various ages after ketamine 75 mg kg" 1 i.p. **• Significant difference between sexes of same age (P< 0.001) using Student's t test.
(P< 0.001) if the rats aged 3-16 weeks were considered. There was no such significant difference in the 1- and 2-week-old rats. The concentrations of ketamine and metabolite I in male rats at the point of recovery decreased with increasing age. Metabolite II did not appear in the plasma until 3 weeks of age and then increased steadily to plateau at about 6 weeks of age, by which time ketamine and metabolite I concentrations had decreased significantly from the 1-week values (fig. 5). In the female rats plasma concentrations followed a pattern similar to those of the male rats, but the
AGE AND SEX IN KETAMINE ANAESTHESIA IN RATS •—• Ketamine o—o Metabolite I ...... Metabolite II
5.0-
D
e 4.0 %
Males Females
•I 3.0H 2
1 2.03
16
6 AGE (weeks)
Ketamine Metabolite I Metabolite II
4.0-
3 o 3.0-
2.0o
S i.oa. 2
4
6
8 10 12 Age (weeks)
14
4
--fU
6
8
10
12
i
14 16
Age (weeks)
FIG. 4. Comparison of sleeping times of male and female rats of different ages following ketamine 75 mg kg" 1 i.p. * Significant difference between sexes of same age (P< 0.05) using Student's t test. •^
•§
16
FIG. 5. Concentration of ketamine and its metabolites found in the plasma of male rats at recovery after ketamine 75 mg kg" 1 i.p. Mean±SEM of six animals except for 1-week group (four).
ketamine concentrations were not significantly less until 8 weeks of age, whilst the metabolite I concentrations were significantly less by 3 weeks of age (fig. 6). Again, metabolite II was not detected in 1and 2-week-old rats, appearing first in the plasma of 3-week-old rats. Concentrations increased to a maximum at 4 weeks and remained unchanged thereafter (fig. 6). Comparison of the plasma concentrations of the drug and its metabolites in both sexes at recovery showed some interesting differences. Ketamine concentrations were consistently greater in the
FIG. 6. Concentration of ketamine and its metabolites found in the plasma of female rats at recovery after ketamine 75 mg kg" 1 i.p. Mean + SEM of six animals except for 1-week group (five).
females, but there was no significant overall difference with age. The concentrations of metabolite I were, in general, greater in the female rats at most age groups; analysis of variance indicated that there was a significant difference between the sexes (P
![Influence of age and sex on the duration of action ketamine in the rat [proceedings].](/assets/img/hold.png)
