[Clinical pharmacokinetics of alfentanyl (author's transl)]

In 7 patients (ASA class I and II) the pharmacokinetic behaviour after bolus injection of alfentanyl was investigated. The plasma decay curves in each patient could be described in terms of an open two-compartment model. The plasma half-life of alfentanyl in the alpha-phase was about 4 min, the elimination half-life was 70 min. The total volume of distribution was calculated to 33 1. The total plasma clearance amounted to 336 ml/min. Plasma protein binding of alfentanyl was about 92%; binding to human erythrocytes showed values less than 0.1%. The renal excretion of unchanged alfentanyl amounted to only 0.4% of the total dose in a time period of 24h. Clinical observations showed a minor effect on cardiovascular system; apnoea was seen in all patients. Chest wall rigidity was the main unwanted effect in 5 of 7 cases. The onset of action could be observed during the injection of 5 mg alfentanyl. The recovery period was extremely short. Therefore, alfentanyl seems to be of advantage for short surgical interventions; for longer lasting anaesthesia the development of an infusion model may be helpful.