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Revex
CLINICAL PHARMACOLOGY
Revex
Pharmacodynamics
REVEX prevents or reverses the effects of opioids, including respiratory depression, sedation, and hypotension. Pharmacodynamic studies have shown that REVEX has a longer duration of action than naloxone at fully reversing doses. REVEX has no opioid agonist activity.
REVEX is not known to produce respiratory depression, psychotomimetic effects, or pupillary constriction. No pharmacological activity was observed when REVEX was administered in the absence of opioid agonists.
REVEX has not been shown to produce tolerance, physical dependence, or abuse potential.
REVEX can produce acute withdrawal symptoms in individuals who are opioid dependent.
Pharmacokinetics
Nalmefene exhibited dose proportional pharmacokinetics following intravenous administration of 0.5 mg to 2.0 mg. Pharmacokinetic parameters for nalmefene after a 1 mg intravenous administration in adult male volunteers are listed in Table 1.
Table 1: Mean (CV%) Nalmefene Pharmacokinetic Parameters In Adult Males Following a 1 mg Intravenous Dose
| Parameter | Young, N=18 | Elderly, N=11 |
| Age | 19-32 | 62-80 |
| Cp at 5 min. (ng/mL) | 3.7 (29) | 5.8 (38) |
| Vdss (L/kg) | 8.6 (19) | 8.6 (29) |
| Vc (L/kg) | 3.9 (29) | 2.8 (41) |
| AUC0-inf (ng-hr/mL) | 16.6 (27) | 17.3 (14) |
| Terminal T1/2 (hr) | 10.8 (48) | 9.4 (49) |
| Clplasma (L/hr/kg) | 0.8 (23) | 0.8 (18) |
Nalmefene was completely bioavailable following intramuscular or subcutaneous administration in 12 male volunteers relative to intravenous nalmefene. The relative bioavailabilities of intramuscular and subcutaneous routes of administration were 101.5% ± 8.1% (Mean ± SD) and 99.7% ± 6.9%, respectively. Nalmefene will be administered primarily as an intravenous bolus, however, nalmefene can be given intra-muscularly (IM) or subcutaneously (SC) if venous access cannot be established. While the time to maximum plasma nalmefene concentration was 2.3 ± 1.1 hours following intramuscular and 1.5 ± 1.2 hours following subcutaneous administrations, therapeutic plasma concentrations are likely to be reached within 5-15 minutes after a 1 mg dose in an emergency. Because of the variability in the speed of absorption for IM & SC dosing, and the inability to titrate to effect, great care should be taken if repeated doses must be given by these routes.
Generic Name: Nalmefene Hydrochloride
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