Alfentanil (Alfentanil Hydrochloride) - Drug Interactions, Contraindications, Overdosage

DRUG INTERACTIONS

Drug Interactions:

Both the magnitude and duration of central nervous system and cardiovascular effects may be enhanced when alfentanil is administered in combination with other CNS depressants such as barbiturates, tranquilizers, opioids, or inhalation general anesthetics. Postoperative respiratory depression may be enhanced or prolonged by these agents. In such cases of combined treatment, the dose of one or both agents should be reduced. Limited clinical experience indicates that requirements for volatile inhalation anesthetics are reduced by 30 to 50% for the first sixty (60) minutes following alfentanil induction.

The concomitant use of erythromycin with alfentanil can significantly inhibit alfentanil clearance and may increase the risk of prolonged or delayed respiratory depression.

Cimetidine reduces the clearance of alfentanil. Therefore smaller alfentanil doses will be required with prolonged administration and the duration of action of alfentanil may be extended.

Perioperative administration of drugs affecting hepatic blood flow or enzyme function may reduce plasma clearance and prolong recovery.

OVERDOSAGE

Overdosage would be manifested by extension of the pharmacological actions of alfentanil (see CLINICAL PHARMACOLOGY) as with other potent opioid analgesics. No experience of overdosage with alfentanil was reported during clinical trials. The intravenous LD₅₀ of alfentanil is 43-51 mg/kg in rats, 72-74 mg/kg in mice, 72-82 mg/kg in guinea pigs and 60-88 mg/kg in dogs. Intravenous administration of an opioid antagonist such as naloxone should be employed as a specific antidote to manage respiratory depression.

The duration of respiratory depression following overdosage with alfentanil may be longer than the duration of action of the opioid antagonist. Administration of an opioid antagonist should not preclude immediate establishment of a patent airway, administration of oxygen, and assisted or controlled ventilation as indicated for hypoventilation or apnea. If respiratory depression is associated with muscular rigidity, a neuromuscular blocking agent may be required to facilitate assisted or controlled ventilation. Intravenous fluids and vasoactive agents may be required to manage hemodynamic instability.

CONTRAINDICATIONS

Alfentanil is contraindicated in patients with known hypersensitivity to the drug or known intolerance to other opioid agonists.