Pharmacokinetic and pharmacodynamic studies on interaction of "Trikatu" with diclofenac sodium.

"Trikatu"-an Ayurvedic formulation comprising of a 1:1:1 ratio of dried fruits of Piper nigrum, Piper longum and dried rhizomes of Zingiber officinale is widely used to enhance the bioavailability of drugs, like vasicine, indomethacin, etc. The enhanced biological response might lead to alteration of therapeutic regimens of commonly prescribed drugs. The present work was aimed to study the effect of concomitant administration of Trikatu on the pharmacokinetics and pharmacodynamics of diclofenac sodium, a frequently prescribed non-steroidal anti-inflammatory drug, having a poor oral bioavailability (54 +/- 2%). The effect of Trikatu on the bioavailability profile of diclofenac sodium was studied in rabbits. It was observed that Trikatu significantly decreased the serum levels of diclofenac sodium. The pharmacodynamic study was carried out to evaluate the effect of Trikatu on the anti-inflammatory activity of diclofenac sodium using carragenin-induced rat paw edema model. It was observed that the mean percent edema inhibition shown by the combination of Trikatu and diclofenac was similar to that shown by Trikatu alone but significantly less than that shown by diclofenac alone. Thus, the experimental findings indicated that Trikatu pretreatment might decrease the bioavailability of certain drugs probably through a drug-herb interaction thereby adversely affecting the therapeutic efficacy of these drugs.