Relative bioavailability of paracetamol suspensions commercially available in Thailand

Abstract

Paracetamol suspensions commercially available in Thailand and an original brand of paracetamol elixir were evaluated both in vitro and in vivo studies. The in vitro absorption study was conducted using the Sartorius Absorption Simulator SM 16750 in which the in vivo transport of the drug was simulated. Results demonstrated that the in vitro absorption rate constants of paracetamol from suspension and from elixir dosage forms were not statistically significant difference (p>0.05). The bioavailability of paracetamol suspensions and an original brand of paracetamol elixir were studied in 8 healthy volunteers, 4 females and 4 males, using a cross over design. A single dose of each dosage form equivalent to 600 milligrams of paracetamol was given to the subjects following an overnight fast. Urine samples were collected for total paracetamol determination at appropriate time interval for 32 hours. The urinary excretion data were analyzed using CSTRIP computer program. Results indicated that paracetamol suspensions and paracetamol elixir were bioequivalent (p>0.05). Relative biavailability of paracetamol suspensions with respect to paracetamol elixir were 104.31, 98.35, 104.12 and 106.74 % for Brands S1, S2, S3 and S4, respectively. The cumulative amount of paracetamol excreted into the urine was about 70 -75% 0f the administered dose and the average half – life of paracetamol was 4.32 hours (4.14 -4.43 hours). The correlation coefficient test showed that the in vitro absorption rate constants and the in vivo absorption rate constants were not related (p>0.05).