Effect of Trikatu, an Ayurvedic Prescription, on the Pharmacokinetic Profile of C,Arbamazepine in Rabbits

Indian J Physiol Pharmacol 1999; 43 (1) : 133-136

EFFECT OF TRIKATU, AN AYURVEDIC PRESCRIPTION, ON THE PHARMACOKINETIC PROFILE OF C,ARBAMAZEPINE IN RABBITS

R. S. KARAN, V. K. BHARGAVA* AND S. K. GARG

Department of Pharmacology, Postgraduate Institute of Medical Education & Research, Chandigarh -160 012

( Received on August 29, 1998)

Abstract: The effect of single and multiple doses of a herbal preparation Trikatu was studied on the bioavailability and pharmacokinetics of carbamazepine in rabbits. Rabbits (n=10) were administered a single dose of carbamazepine (80mg/kg; p.o.) and after a washout period of 7 days in combination with a single dose of Trikatu (500mg/kg; p.o.). In the other study, six rabbits were administered a single dose of carbamazepine (80mg/ kg; p.o.) before and after multiple doses of Trikatu (500mg/kg X 7d; p.o.). The blood samples were collected at 0, 1, 2, 4, 6, 9, 12 and 24 hours after drug administration and assayed for carbamazepine. In the animals treated

with single dose of Trikatu, there was a significant decrease in T max of carbamazepine (P<0.05). Multiple doses of Trikatu also shortened the T max of carbamazepine although not to statistically significant level. Our results suggest that the steeper rise and fall in the plasma levels of carbamazepine brought about by Trikatu, do not constitute significant advantage.

Key words: trikatu carbamazepine interaction

INTRODUCTION and rifampicin when coadministered with Trikatu or piperine 0-3). The enhanced Trikatu® a commonly used herbal plasma levels of drugs has been attributed preparation in Ayurvedic medicine, consists to an increase in the rate of absorption of of three crude drugs namely dried fruits of drugs and to a non specific inhibition of black pepper (piper nigrum Linn.), dried drug metabolising enzymes by piperine (2,3). fruits of long pepper (piper longum Linn.) It has been shown to inhibit arylhydro and dried rhizomes of ginger (Zingiber carbon hydroxylation, ethylmorphine-N officinalis Rose.) in the ratio of [1:1:1; w/wJ demethylation, 7-ethoxycoumarin-o (1.). The active principle of piper species is deethylation and 3-hydroxybenzo(a) pyrene an alkaloid piperine or 1-peperoyl glucuronidation (4-5). Carbamazepine is a piperidine. Several studies have reported first line drug for the management of partial enhancement of blood levels of drugs like and tonic-clonic seizures. Because of limited vasicine, sparteine, phenytoin, propranolol, aqueous solubility, carbamazepine is theophylline, sulphadiazine, tetracycline absorbed slowly and erratically after oral *Corresponding Author 134 Karan et al Indian J Physiol Pharmacol 1999; 43(1) administration (6). The present study was with Trikatu (500 mg/kg; p.o.) was given. planned to see the effect of single and Blood samples were collected at similar time multiple doses of Trikatu on the intervals as on day 1. pharmacokinetics of carbamazepine. Plasma was separated and stored at METHODS -20°C until assayed for carbamazepine by the HPLC method (7). The sensitivity of the The study was carried out in male assay method was 0.1 pg/ml. The intra assay Newzealand white rabbits 0.5-2.5 kg). The coefficient of variation at 0.5 pg/ml and 16 animals were maintained on a standard pg/ml were 6.83% and 4.96% respectively. laboratory diet and were housed at ambient The interassay coefficient of variation at the temperature. All drug administrations same concentration were B.41 % and 6.72% were done at B a.m. Trikatu (500mg) respectively. Peak plasma concentration

) containing 10mg of pure active principle [C ma and time to reach the peak plasma piperine (available commercially) and concentration ['I'm,,) were calculated from carbamazepine (Sigma Chemicals, USA) in the actual plasma data. Rate constant for pure powder form were used in the study. elimination i.e. kel was calculated by regression analysis of the monoexponential Single dose study: declining line of the log plasma drug concentration versus time graph, while After overnight fasting, ten rabbits elimination half life (t1/2el) was obtained received carbamazepine (BOmg/kg; p.o.) from the formula tl/2el = 0.693/kel (B). Area through an intragastric tube. Blood samples under the plasma drug concentration versus time curve (AUC _ ) was calculated by the were collected in heparinized tubes from the O t marginal ear vein at 0, 1, 2, 4, 6, 9, 12 and trapezoidal rule. Extension of the AUC data _) 24 hours after drug administration. The to infinity (AUC t was done by dividing rabbits, after a washout period of 7 days the last observed concentration of drug in were administered carbamazepine (BO mg/ plasma by the elimination rate constant (kel). AUC _ was the sum of AUC _ and kg; p.o.) alongwith Trikatu (500 mg/kg; p.o.). o u O t _ ' Blood samples were drawn at similar time AUC t u The data was statistically analysed intervals as with carbamazepine alone. by employing the students paired "t" test.

Multiple dose study: RESULTS

After an overnight fast, six rabbits were Fig. 1 compares the plasma concentr administered carbamazepine (BO mg/kg; p.o.) ation (mean ± s.e.m.) of carbamazepine at on day 1. Blood samples were collected at different time intervals, when given alone 0, 1, 2, 4, 6, 9, 12 and 24 hours after drug or with single dose of Trikatu. In the administration. From day 2 to day 7, rabbits absorption phase, Trikatu significantly were treated with Trikatu (500 mg/kg; p.o.) enhanced (P<0.05) the plasma concentration once daily. On day B, after an overnight of carbamazepine at 1, 2 and 4 hours after fast, carbamazepine (BO mg/kg; p.o.) along drug administration. However no significant Indian J Physiol Pharmacol 1999; 43(1) Trikatu-Carbamazepine Interaction 135 ".------

. -CBl ,. -CBZ - CBl~Trjka!u - CBZ~Tnka1u

.l-~~~====~ .1..--,-,-,-,-.-,-.-.-,-.-,-,-u-,,-'-'-,,--=-,,-,:-,--::,,:-:,,-..=---:-,:-,-::,,--:,::-,:,. o I 2 :) • ~ • 7 • • ~ 11 12 I) t.. IS I. H 'I ft 20 21 l1 ~1 .. .& Tlme(h) ""'''''' Fig. 1: Mean plasma concentration of carbamazepine Fig. 2: Mean plasma concentration of carbamazepine (CBZ, 80 mg/kg, p.o) and carbamazepine + (CBZ, 80 mg/kg, p.o) before and after multiple Trikatu (500 mg/kg. p.o.) in rabbits (n=10;* = doses of Trikatu (500 mg/kg, p.o.) in rabbits P<0.05), (n=6;* = P<0.05).

TABLE r : Carbamazepine kinetics before and after pharmacokinetic parameters (mean ± s.e.m.) single oral dose of Trikatu. of carbamazepine before and after multiple doses of Trikatu. No significant difference Pharmacokinetic Carbamazepine Carbamazepine was observed in any of the pharmacokinetic parameters + Trikatu parameters calculated.

Cm.. lug/roll 9.38 ± 0.78 1O.46± 0.38 TABLE II Carbamazepine kinetics before and after T m". (h) 6.00 ± 0.58 3.00± 0.42* multiple oral doses of Trikatu. Kel (h- ) ' 0.22 ± 0.04 0.22± 0.03 t1/2 el (h) 3.95 ±0.54 3.75± 0.52 Pharmacokinetic Ca.rbamazepine Carbamazepine parameters + Trika.tu AUCo-u (pg/ml.h) 92.21 ± 10.45 84.84± 10.42

,. C m (ug/rol) 9.67 ± 0.69 10.61± 0.73 Values represent mean ± SEM (n=10; *P<0.05) T ..d' (h) 4.00 ± 0.73 3.67± 0.61 Kel (h-') difference was observed in the elimination 0.22 ± 0.03 0.27± 0.03 phase. Table 1 compares pharmacokinetic t1/2 el (h) 3.54 ± 0.58 2.83± 0.37 ALCo~, (ug/ml.h) 78.78 ± 7.61 73.77± 6.25 parameters (mean ± s.e.m.) of carbama zepine before and after single oral dose of Values represent mean ± SEM (n=6)

Trikatu. T max in the Trikatu + carbamazepine group was significantly lower (P

Trikatu treatment were significantly higher absorption phase and a shorter T m.. in the at 1 and 4 hours. Table II compares various Trikatu group. Similar pharmacokinetic 136 Karan et al Indian J Physiol Pharmacol 1999; 43(1) changes have been reported for drugs like The shortening of the T max by multiple phenytoin, propranolol and theophylline, doses of Trikatu was not statistically when given along with piperine. However significant. This could be attributed to a the increase in the rate of absorption smaller sample size (n=6) as compared to brought about by piperine has not been the single dose study (n=10). explained so far (2, 3). We believe it could be because of increased splanchnic blood The results further show that single dose flow and rate of transport of drugs across of Trikatu did not significantly alter the the gastrointestinal mucous brought about AUCo_a and tl/2 el of carbamazepine. These by Trikatu (9). The other important actions findings do not correspond with the reported of Trikatu on the gastrointestinal tract bioavailability enhancing action of Trikatu. include its ability to increase the gastric One possible inference is that the pH and delay the gastric emptying (9). cytochrome P-450 isoenzymes involved in However carbamazepine is a highly carbamazepine metabolism may have a low lipophilic, neutral compound and does not or no affinity for piperine. It is also possible ionize in an aqueous environment (10). Thus that the isoenzymes responsible for the the latter two effects of Trikatu on the metabolism of carbamazepine in rabbits may gastrointestinal tract probably did not have different substrate specificities (11). contribute to the enhanced absorption of carbamazepine. The metabolism of To conclude, the steeper rise and fall in carbamazepine follows first order kinetics, the plasma levels of carbamazepine along which explains the steep fall in plasma _ with no change in the AUCO a and tl/2 el carbamazepine levels during the elimination brought about by Trikatu co-administration, phase in the Trikatu treated group. has no significant advantage. REFERENCES

1. Zutshi RK, Singh R, Zutshi U, Johri RK, Atal CK. Molinoff PE, Ruddon RW, Gilman AG, editors. Influence of piperine on rifampicin blood levels in Goodman & Gilman's. The phrmacological basis of patients of pulmonary tuberculosis. J Ass Phys therapeutics. 9th ed., New York, McGraw-Hill India 1985; 33: 223-224. 1996: 461-486. 2. Bano G. Amla V, Raina RK. The effect of piperine 7. Joshi MV, Pohujani SM, Kshirsagar NA, Shah PH, on kinetics of phenytoin in healthy volunteers. Acharya VN. Simultaneous HPLC measurements Planta Medica 1987; 53: 568-569. of phenobarbitone, phenytoin and carbamazepine 3. Bano G, Raina RK, Zutshi U, Bedi KL. Effect of from plasma samples. Indian J Pharmacol 1990; piperine on the bioavailability and 22: 177-179. pharmacokinetics of propranolol and theophylline 8. Gibaldi M. Biopharmaceutics and clinical in healthy volunteers. Eur J Clin Pharmacal 1991; pharmacokinetics. 3rd ed., Philadelpia, Lea & 41: 615-617. Febiger 1984: 29-155. 4. Atal CK, Dubey RK, Singh J. Biochemical basis of 9. AnnamaJai AR, Manavalan R. Effects of Trikatu enhanced drug bioavailability by piperine. Evidence and its individual components and piperine on that piperine is a potent inhibitor of drug gastrointestinal tract. Indian Drugs 1990; 27: 595 metabolism. J Pharmacol Exp Ther 1985; 232: 258 262. 604. 5. Singh J. Dubey RK, Atal CK, Piperine mediated 10. Eadie MJ, Tyrea JH. Anticonvulsant inhibition of glucuronidation activity in isolated Therapy: pharmacological basis and therapeutics. epithetial cells of the guinea pig small 3 I'd ed., Edinburg, churchill livingstone 1989: 137 intestine: Evidence that piperine lowers the 172. endogenous UDP-glucuronic acid content. J 11. Nebert DW, David RN, Coon MJ, Estabrook RW. pharmacol Exp Ther 1986; 236: 488-493. The P 450 superfamily: Update on new sequences, 6. McNamara J O. Drugs effective in the therapy of gense mapping and recommended nomenclature. the epilepsies. In: Hardman JG, Limbird LE, DNA Cell Bioi 1991; 10: 1-14.