EFFECT OF CAFFEINE ON PHARMACOKINETICS OF PARACETAMOL IN HEALTHY HUMAN VOLUNTEERS: A CASE STUDY OF PANADOL EXTRA

EFFECT OF CAFFEINE ON PHARMACOKINETICS OF PARACETAMOL IN HEALTHY HUMAN VOLUNTEERS: A CASE STUDY OF PANADOL EXTRA

Abstract:

Acetaminophen or paracetamol is an analgesic and anti-pyretic agent widely used for treatment of headaches, minor pains and in combination with other medications like cold remedies and opoid analgesics. Individuals with headaches and minor pains tend to use paracetamol with caffeine combinations than paracetamol alone in their treatment due to faster relief. However, the pharmacokinetic rationale for use is still unclear. The aim of this study was to determine the effect of caffeine on pharmacokinetics of paracetamol in Panadol Extra® tablets using healthy human volunteers. Three different batches of Panadol® and Panadol Extra® tablets sourced from retail outlets within Zaria were analysed qualitatively using in vitro analysis which include weight uniformity test, friability test, chemical assay, dissolution test, disintegration test and also for the pharmacokinetic studies. Standard paracetamol powder was used for pilot study and to validate the modification of Glynn and Kendal method using spiked aqueous samples with known concentrations of paracetamol and a calibration curve was plotted. Twelve (12) healthy volunteers of both sexes within the age of 20-29 years took part in the study. It was a single blind, cross over study with wash out period of two weeks. Each volunteer was administered 1g tablets of both test samples containing paracetamol orally with 200ml of water after fasting overnight and saliva was sampled at different time intervals up to six (6) hours. The samples were analyzed for presence of paracetamol using the Glynn and Kendal method modified by Shihana by taking their absorbances with a UV spectrophotometer at 430nm. The results were compared using the independent student‟s t- test between the samples. P value less than 0.05 was considered significant. All the six batches of samples studied passed in vitro tests for paracetamol except for a sample of Panadol Extra® tablets that failed the friability test. The pharmacokinetic parameters compared showed variable values. However consistently higher saliva paracetamol concentrations ranging from 22.20 to 25.20 μg/ml were seen with all samples of Panadol Extra® tablets which was statistically significant (p ≤ 0.05) compared to Panadol® tablets which ranged from 20.60 – 22.50 μg/ml. All the other values calculated did not show statistical significant difference when compared. This study has therefore shown that Panadol Extra® tablets and Panadol® tablets are chemically equivalent for the paracetamol component and possess varying values of pharmacokinetic parameters. This was indicated by the significantly higher saliva paracetamol levels for Panadol Extra® tablets as compared to Panadol® tablets and may be concluded that caffeine in Panadol Extra® tablets is responsible.

EFFECT OF CAFFEINE ON PHARMACOKINETICS OF PARACETAMOL IN HEALTHY HUMAN VOLUNTEERS: A CASE STUDY OF PANADOL EXTRA