PubMed · 9613169
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F Fekete. 1998-05-10. [Paracetamol].. https://pubmed.ncbi.nlm.nih.gov/9613169/
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The pharmacokinetics of acetaminophen have been well studied in different populations, especially in Caucasians. However, limited studies on acetaminophen pharmacokinetics have been conducted in the native Chinese and few such data have been reported in the English language literature. Previous published studies suggested that environmental and genetic factors may cause inter-individual difference in acetaminophen disposition, thus we investigated the pharmacokinetics of acetaminophen in Hong Kong Chinese subjects. A single 500 mg oral dose of acetaminophen was administered to 12 healthy male Chinese subjects under fasting conditions. Multiple blood samples were obtained after drug administration. Plasma acetaminophen concentrations were determined using HPLC, and its main pharmacokinetic parameters were generated. In comparison to other published data, acetaminophen half-life was considerably longer (15-62%), and oral clearance was lower (16-56%) in Hong Kong Chinese as compared to Australian Chinese, Caucasians (USA, UK, Australia), and subjects from Pakistan, Denmark, Spain and South Africa. Similarities however were found in the pharmacokinetic parameters between Hong Kong Chinese and Mainland Chinese subjects. The observed pharmacokinetic parameters of acetaminophen in Hong Kong Chinese subjects may be different from other ethnic populations. Further studies are needed to verify this hypothesis.
This study was designed to elucidate the mechanism of retinol's potentiation of acetaminophen-induced hepatotoxicity. To accomplish this, the major bioactivation and detoxification pathways for acetaminophen were investigated following retinol (75 mg/kg/day, 4 days), acetaminophen (400 mg/kg), and retinol + acetaminophen treatment. Hepatic microsomes were used to determine the catalytic activity and polypeptide levels of cytochrome P450 enzymes involved in the murine metabolism of acetaminophen. Results showed that the catalytic activity and polypeptide levels of CYP1A2, CYP2E1, and CYP3A were unchanged in the treatment groups compared to vehicle and untreated controls. In combination, retinol + acetaminophen caused a significantly greater depletion of GSH compared to corn oil + acetaminophen (0.36 +/- 0.11 vs 0.89 +/- 0.19 micromol/g, respectively, p < 0.05). This greater GSH depletion correlated with a higher degree of hepatic injury in the retinol + acetaminophen-treated animals but is probably not the cause of the potentiated injury since the results showed that retinol treatment itself did not alter hepatic glutathione (3.34 +/- 0.43 vs 3.44 +/- 0.46 micromol/g for retinol vs vehicle, respectively). However, hepatic UDPGA stores were decreased in the retinol-treated group compared to untreated and corn oil controls (54.6 +/- 10.6 vs 200.6 +/- 17.6 nmol/g for retinol and untreated control, respectively, p < 0.001). This demonstrates that there is significantly less hepatic UDPGA available for conjugation following retinol administration. The results suggest that decreased hepatic UDPGA is likely the cause of retinol's potentiation of acetaminophen-induced hepatic injury.
In patients suspected of having drug-induced immune thrombocytopenia, antibodies reactive with normal platelets in the presence of the suspect drug can sometimes be identified, but negative results are often obtained. One reason for this is that drug metabolites, formed in vivo, can be the sensitizing agents, but very little is known about the specific metabolites that can cause this complication. Five patients were studied who developed thrombocytopenia after taking the nonsteroidal anti-inflammatory drug naproxen (3 cases) or acetaminophen (2 cases) but in whom drug-dependent antibodies could not be detected by means of the unmodified drugs. In each case, antibodies that reacted with normal target platelets in the presence of a known drug metabolite (naproxen glucuronide or acetaminophen sulfate) were identified. Four of the antibodies were specific for the glycoprotein (GP) IIb/IIIa complex, but one acetaminophen sulfate-dependent antibody reacted preferentially with GPIb/IX/V. In patients with a clinical picture suggestive of drug-induced immune thrombocytopenia, tests for metabolite-dependent antibodies can be helpful in identifying the responsible agent. (Blood. 2001;97:3846-3850)