Pharmacokinetics of zimelidine in humans ? Plasma levels and urinary excretion of zimelidine and norzimelidine after intravenous and oral administration of zimelidine

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Abstract
Five healthy adults were administered zimelidine orally (150 mg) and by intravenous infusion (20 mg) in a crossover design. Blood and urine samples were collected for a period of 28 hours after dosing and the concentrations of zimelidine and norzimelidine determined. There was no significant difference in terminal phase half-life of zimelidine after oral (4.7 h±1.3 SD) or intravenous dosing (5.1 h±0.7 SD). An average of 50% of the ingested oral dose reached the systemic circulation. Excretion of unchanged zimelidine in urine was on average 1.26% of the intravenous dose. In appears that zimelidine is completely absorbed from the gastrointestinal tract and “first-pass metabolism” in the liver reduces the bioavailability to 50%. The mean plasma half-life for norzimelidine was 22.8 h. The area under the plasma concentration time curve for norzimelidine after oral administration was 92% of that after intravenous administration. The plasma concentration of both zimelidine and norzimelidine are predicted to approach steady-state within 3–5 days.