This study is to determine the pharmacokinetics (how the body absorbs, breaks down and eliminates drug from your body) of nalmefene when given intranasally (IN;into the nose) compared to a dose of nalmefene when given intramuscularly (IM; into the muscle); to compare the blood levels of nalmefene when given IN to nalmefene when given IM; and to evaluate the safety and tolerability of nalmefene IN.

Open-label, randomized, 2-period, 2-treatment, 2-sequence, crossover study in 68 healthy volunteers. Subjects will be assigned to each of the 2 possible sequences. Each subject will receive 2 treatments during the 2 dosing periods: Intranasal (IN) dose of 3 mg nalmefene hydrochloride and intramuscular (IM) dose of 1.0 mg nalmefene, with a 4 day washout period between doses. Screening can occur up to 28 days before baseline admission, subjects will then stay in the inpatient facility for 7 days to complete the treatment phase of the study and will be discharged following completion of the discharge procedures at the end of the last period. Subjects will be called 3 to 5 days after discharge to inquire concerning Adverse Events (AEs) and concomitant medications since discharge.

Inclusion Criteria:

• Male or female aged 18 to 55 years inclusive
• BMI ranging from 18 to 30 kg/m2, inclusive
• Adequate venous access
• Subjects must be non-smokers

Exclusion Criteria:

• History of clinically significant disease
• Significant trauma injury, major surgery, open biopsy within 30 days prior to screening
• Following an abnormal diet 4 weeks prior to screening
• Use of over the counter medications, dietary supplements, herbal products, vitamins or opioid analgesics 14 days before intervention
• Use of enzyme altering drugs 30 days before intervention
• Use of nasal products 28 days before intervention and throughout the study
• Previous or current opioid, alcohol, or other drug dependence
• Donated or received blood 30 days before intervention
• Women who are pregnant or breastfeeding at screening
• Women of childbearing potential unless surgically sterile or use effective contraception
• Current or recent upper respiratory tract infection
• Allergic to nalmefene

Subjects in the study from baseline to 7 days with a =3 to 5 day follow-up