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Pharmacology: Oxpentifylline and its metabolites improve the flow properties of blood. In patients with occlusive arterial disease, oxpentifylline increases blood flow to the affected microcirculation and enhances tissue oxygenation. Oxpentifylline administration has been shown to produce dose-related hemorheologic effects, lowering blood viscosity, and improving erythrocyte flexibility. It also reduces plasma fibrinogen levels and inhibits platelet aggregation. Tissue oxygen levels have been shown to be significantly increased by therapeutic doses of oxpentifylline in patients with peripheral arterial disease.
Pharmacokinetics: On oral administration, oxpentifylline is almost completely absorbed and undergoes first-pass metabolism producing various metabolites which appear in plasma very soon after dosing. Peak plasma levels of the parent compound and its metabolites are reached within 1 hour. The major metabolites are Metabolite 1 (1-[5-hydroxyhexyl]-3,7-dimethylxanthine) and Metabolite V (1-[3-carboxypropyl]-3,-7-dimethylxanthine), and plasma levels of these metabolites are 5 and 8 times greater, respectively, than oxpentifylline.
The apparent plasma half-life of oxpentifylline varies from 0.4 to 0.8 hours and the apparent plasma half-life of its metabolites vary from 1 to 1.6 hours. Excretion is almost totally urinary; essentially no parent drug is found in the urine. Less than 4% of the administered dose is recovered in faeces.
Administration of the 400 mg controlled release Flexital tablet produces plasma levels of the parent compound and its metabolites within 2 to 4 hours which remain constant over an extended period of time. The controlled release of oxpentifylline from the tablet eliminates peaks and troughs in plasma levels and improves gastrointestinal tolerance.
