Single dose primaquine has no effect on paracetamol clearance

Effect of an experimental malaria infection on the metabolism of phenacetin in the rat isolated perfused liver

1. The effect of infection with the rodent malaria parasite Plasmodium berghei on the metabolism of phenacetin has been investigated in a rat isolated perfused liver preparation. 2. A bolus dose of phenacetin (10 mg) was introduced into the perfusate reservoir of both control (n = 4) and malaria-infected (n = 4) liver preparations, and samples of bile and perfusate were collected (0-4 h) for hplc analysis of phenacetin, paracetamol and its phase II metabolites. 3. Whereas malaria had no effect on the hepatic clearance of phenacetin (control: 0.64 +/- 0.15 versus malaria: 0.66 +/- 0.14 ml min-1), there was a significant reduction in the hepatic clearance of generated paracetamol (control: 1.22 +/- 0.15 versus malaria: 0.41 +/- 0.08 ml min-1) and the total recovery in bile and perfusate of paracetamol glucuronide (control: 1.18 +/- 0.44 versus malaria: 0.29 +/- 0.20 mg). There was no significant change during malaria infection in the total recovery of either phenacetin (control: 1.30 +/- 0.73 versus malaria: 0.79 +/- 0.36 mg) or paracetamol sulphate (control: 0.81 +/- 0.25 versus malaria: 0.74 +/- 0.16 mg),

Effect of malaria infection on the pharmacokinetics of paracetamol in rat

1. Paracetamol (P; 50 and 300 mg/kg i.v.) was administered to the control and malaria-infected (MI) male Wistar rat in order to assess the effect of MI on the metabolism of paracetamol to its glucuronide (PG) and sulphate (PS) conjugates and their excretion in urine. 2. At a dose of 50 mg/kg, neither total clearance (ClT) (controls, 20.3 +/- 0.5; MI, 19.9 +/- 0.9, ml/min/kg; mean +/- SD, p > 0.05) nor the renal clearance of P (ClR) were affected by MI. Although the formation clearance of PG (Clf PG) was decreased by about 40% (controls, 6.6 +/- 1.1; MI, 3.9 +/- 0.9, ml/min/kg, p < 0.05), the formation clearance of PS (Clf PS) was increased by 30% in the MI rat (controls, 8.8 +/- 0.9; MI, 11.2 +/- 1.7, ml/min/kg, p < 0.05), and therefore Clm (controls, 19.7 +/- 0.5; MI, 19.2 +/- 0.8, ml/min/kg, p > 0.05) was unchanged by MI. 3. At a dose of 300 mg/kg, MI produced a significant decrease in the total clearance of P (ClT) (controls, 16.9 +/- 1.0; MI, 11.9 +/- 0.9, ml/min/kg, p < 0.05), metabolic clearance (Clm) (controls, 15.9 +/- 1.4; MI, 11.3 +/- 0.9, ml/min/kg, p < 0.05) and the formation clearance of PG (Clf PG) (controls, 7.9 +/- 1.3; MI, 4.7 +/- 1.5, ml/min/kg, p < 0.05) without affecting Clf PS and ClR of P. 4. These findings indicate that MI impairs the glucuronidation of paracetamol in rat in vivo at both the low and high doses of P. Increased sulphate formation appeared to compensate for decreased glucuronidation at the lower dose.(ABSTRACT TRUNCATED AT 250 WORDS)