Nalmefene

INDICATIONS AND USAGE OPVEE nasal spray is indicated for the emergency treatment of known or suspected overdose induced by natural or synthetic opioids in adults and pediatric patients aged 12 years and older, as manifested by respiratory and/or central nervous system depression. OPVEE nasal spray is intended for immediate administration as emergency therapy in settings where opioids may be present. OPVEE nasal spray is not a substitute for emergency medical care. OPVEE nasal spray is an opioid antagonist indicated for the emergency treatment of known or suspected overdose induced by natural or synthetic opioids in adults and pediatric patients aged 12 years and older, as manifested by respiratory and/or central nervous system depression. OPVEE nasal spray is intended for immediate administration as emergency therapy in settings where opioids may be present. OPVEE nasal spray is not a substitute for emergency medical care.

DOSAGE AND ADMINISTRATION Important Information - Dosage Forms Nalmefene Hydrochloride Injection is supplied in two concentrations that can be identified by their color coded container labels: a concentration suitable for postoperative use (100 µg/mL) in a blue labeled vial containing ONE (1) mL and a concentration suitable for the management of overdose (1 mg/mL, 10 times as concentrated, 20 times as much drug) in a green labeled vial containing TWO (2) mL. Proper steps should be taken to prevent use of the incorrect concentration. General Principles Nalmefene hydrochloride injection should be titrated to reverse the undesired effects of opioids. Once adequate reversal has been established, additional administration is not required and may actually be harmful due to unwanted reversal of analgesia or precipitated withdrawal. Duration of Action The duration of action of nalmefene hydrochloride injection is as long as most opioid analgesics. The apparent duration of action of nalmefene hydrochloride injection will vary, however, depending on the half-life and plasma concentration of the narcotic being reversed, the presence or absence of other drugs affecting the brain or muscles of respiration, and the dose of nalmefene hydrochloride injection administered. Partially reversing doses of nalmefene hydrochloride injection (1 µg/kg) lose their effect as the drug is redistributed through the body, and the effects of these low doses may not last more than 30-60 minutes in the presence of persistent opioid effects. Fully reversing doses (1 mg/70 kg) have been shown to last many hours in both experimental and clinical studies, but may complicate the management of patients who are in pain, at high cardiovascular risk, or who are physically dependent on opioids. The recommended doses represent a compromise between a desirable controlled reversal and the need for prompt response and adequate duration of action. Using higher dosages or shorter intervals between incremental doses is likely to increase the incidence and severity of symptoms related to acute withdrawal such as nausea, vomiting, elevated blood pressure, and anxiety. Patients Tolerant to or Physically Dependent on Opioids Nalmefene hydrochloride injection may cause acute withdrawal symptoms in individuals who have some degree of tolerance to and dependence on opioids. These patients should be closely observed for symptoms of withdrawal following administration of the initial and subsequent injections of nalmefene hydrochloride injection. Subsequent doses should be administered with intervals of at least 2-5 minutes between doses to allow the full effect of each incremental dose of nalmefene hydrochloride injection to be reached. Recommended Doses for Reversal of Postoperative Opioid Depression Use 100 µg/mL dosage strength (blue label) and see Table 2 for initial doses. The goal of treatment with nalmefene hydrochloride injection in the postoperative setting is to achieve reversal of excessive opioid effects without inducing a complete reversal and acute pain. This is best accomplished with an initial dose of 0.25 µg/kg followed by 0.25 µg/kg incremental doses at 2-5 minute intervals, stopping as soon as the desired degree of opioid reversal is obtained. A cumulative total dose above 1.0 µg/kg does not provide additional therapeutic effect. Table 2: Reversal of Postoperative Opioid Depression Body Weight mL of Nalmefene 100 µg/mL Solution 50 kg 0.125 60 kg 0.150 70 kg 0.175 80 kg 0.200 90 kg 0.225 100 kg 0.250 In cases where the patient is known to be at increased cardiovascular risk, it may be desirable to dilute Nalmefene Hydrochloride Injection 1:1 with saline or sterile water and use smaller initial and incremental doses of 0.1 µg/kg. Management of Known or Suspected Opioid Overdose Use 1.0 mg/mL dosage strength (green label). The recommended initial dose of nalmefene hydrochloride injection for non-opioid dependent patients is 0.5 mg/70 kg. If needed, this may be followed by a second dose of 1.0 mg/70 kg, 2-5 minutes later. If a total dose of 1.5 mg /70 kg has been administered without clinical response, additional Nalmefene Hydrochloride Injection is unlikely to have an effect. Patients should not be given more nalmefene hydrochloride injection than is required to restore the respiratory rate to normal, thus minimizing the likelihood of cardiovascular stress and precipitated withdrawal syndrome. If there is a reasonable suspicion of opioid dependency, a challenge dose of nalmefene hydrochloride injection 0.1 mg/70 kg should be administered initially. If there is no evidence of withdrawal in 2 minutes, the recommended dosing should be followed. Nalmefene hydrochloride injection had no effect in cases where opioids were not responsible for sedation and hypoventilation. Therefore, patients should only be treated with Nalmefene Hydrochloride Injection when the likelihood of an opioid overdose is high, based on a history of opioid overdose or the clinical presentation of respiratory depression with concurrent pupillary constriction. Repeated Dosing Nalmefene hydrochloride injection is the longest acting of the currently available parenteral opioid antagonists. If recurrence of respiratory depression does occur, the dose should again be titrated to clinical effect using incremental doses to avoid over-reversal. Hepatic and Renal Disease Hepatic disease and renal failure substantially reduce the clearance of nalmefene (see Pharmacokinetic s ). For single episodes of opioid antagonism, adjustment of nalmefene hydrochloride injection dosage is not required. However, in patients with renal failure, the incremental doses should be delivered slowly (over 60 seconds) to minimize the hypertension and dizziness reported following the abrupt administration of nalmefene to such patients. Loss of Intravenous Access Should intravenous access be lost or not readily obtainable, a pharmacokinetic study has shown that a single dose of nalmefene hydrochloride injection should be effective within 5-15 minutes after intramuscular or subcutaneous doses of 1.0 mg. (see Pharmacokinetics .)

WARNINGS AND PRECAUTIONS Risk of Recurrent Respiratory and Central Nervous System Depression : While the duration of action of nalmefene is as long as most opioids, a recurrence of respiratory depression is possible, therefore, keep patient under continued surveillance and administer repeat doses of OPVEE using a new nasal spray with each dose, as necessary, while awaiting emergency medical assistance ( 5.1 ) Limited Efficacy with Partial Agonists or Mixed Agonist/Antagonists : Reversal of respiratory depression caused by partial agonists or mixed agonists/antagonists, such as buprenorphine and pentazocine, may be incomplete. Larger or repeat doses may be required. ( 5.2 ) Precipitation of Severe Opioid Withdrawal : Use in patients who are opioid dependent may precipitate opioid withdrawal. In neonates, opioid withdrawal may be life-threatening if not recognized and properly treated. Monitor for the development of opioid withdrawal. ( 5.3 ) Risk of Cardiovascular (CV) Effects : Abrupt postoperative reversal of opioid depression may result in adverse CV effects. These events have primarily occurred in patients who had preexisting CV disorders or received other drugs that may have similar adverse CV effects. Monitor these patients closely in an appropriate healthcare setting after use of nalmefene hydrochloride. ( 5.3 ) Risk of Opioid Overdose from Attempts to Overcome the Blockade : Attempts to overcome opioid withdrawal symptoms caused by opioid antagonists with high or repeated doses of exogenous opioids may lead to opioid intoxication and death ( 5.4 ) 5.1 Risk of Recurrent Respiratory and Central Nervous System Depression Respiratory depression in the community overdose setting may be complex and involve the effects of multiple or unknown drugs, some of which may be long-acting opioids. While the duration of action of nalmefene is as long as most opioids, a recurrence of respiratory depression is possible, even after an apparently adequate initial response to OPVEE nasal spray treatment [See Clinical Pharmacology, Pharmacodynamics (12.3) ] . Therefore, it is necessary to seek emergency medical assistance immediately after administration of the first dose of OPVEE nasal spray and to keep the patient under continued surveillance. A second dose may be necessary if there is recurrence of symptoms of opioid overdose. Additional supportive and/or resuscitative measures may be helpful while awaiting emergency medical assistance [see Dosage and Administration (2.2) ]. 5.2 Risk of Limited Efficacy with Partial Agonists or Mixed Agonist/Antagonists Reversal of respiratory depression by partial agonists or mixed agonist/antagonists such as buprenorphine and pentazocine, may be incomplete. Repeat doses of OPVEE nasal spray may be required to antagonize buprenorphine because the latter has a long duration of action due to its slow rate of binding and subsequent slow dissociation from the opioid receptor [see Dosage and Administration (2.3) ] . Buprenorphine antagonism is characterized by a gradual onset of the reversal effects and a decreased duration of action of the normally prolonged respiratory depression. 5.3 Precipitation of Severe Opioid Withdrawal The use of OPVEE in patients who are opioid dependent may precipitate opioid withdrawal characterized by the following signs and symptoms: body aches, diarrhea, tachycardia, fever, runny nose, sneezing, piloerection, sweating, yawning, nausea or vomiting, nervousness, restlessness or irritability, shivering or trembling, abdominal cramps, weakness, and increased blood pressure. Abrupt postoperative reversal of opioid depression after using OPVEE may result in nausea, vomiting, sweating, tremulousness, tachycardia, hypotension, hypertension, seizures, ventricular tachycardia and fibrillation, pulmonary edema, and cardiac arrest. Death, coma, and encephalopathy have been reported as sequelae of these events. These events have primarily occurred in patients who had pre-existing cardiovascular disorders or received other drugs that may have similar adverse cardiovascular effects. After use of OPVEE, monitor patients with pre-existing cardiac disease or patients who have received medications with potential adverse cardiovascular effects for hypotension, ventricular tachycardia or fibrillation, and pulmonary edema in an appropriate healthcare setting. It has been suggested that the pathogenesis of pulmonary edema associated with the use of nalmefene is similar to neurogenic pulmonary edema, i.e., a centrally mediated massive catecholamine response leading to a dramatic shift of blood volume into the pulmonary vascular bed resulting in increased hydrostatic pressures. OPVEE is not indicated for use in patients less than 12 years of age. In neonates, opioid withdrawal may be life-threatening if not recognized and properly treated and may include the following signs and symptoms: convulsions, excessive crying, and hyperactive reflexes. Monitor the patient for the development of the signs and symptoms of opioid withdrawal. There may be clinical settings, particularly the postpartum period in neonates with known or suspected exposure to maternal opioid use, where it is preferable to avoid the abrupt precipitation of opioid withdrawal symptoms. In these settings, use an alternative, opioid antagonist product that can be titrated to effect and, where applicable, dosed according to weight. [see Use in Specific Populations (8.4) ] . 5.4 Risk of Opioid Overdose from Attempts to Overcome the Blockade OPVEE is unlikely to produce acute withdrawal symptoms in non-opioid dependent patients. The use of OPVEE nasal spray in patients who are opioid dependent may precipitate opioid withdrawal. Attempting to overcome opioid withdrawal symptoms caused by opioid antagonists with high or repeated doses of exogenous opioids could lead to opioid intoxication and death. Inform patients of the potential consequences of trying to overcome the opioid blockade. Get emergency medical assistance as soon as possible after use of OPVEE nasal spray regardless of withdrawal symptoms.

CONTRAINDICATIONS ZURNAI is contraindicated in patients known to be hypersensitive to nalmefene hydrochloride or to any other ingredients in the product. Hypersensitivity to nalmefene hydrochloride or to any other ingredients in ZURNAI. ( 4 )

Drug Interactions Nalmefene hydrochloride injection has been administered after benzodiazepines, inhalational anesthetics, muscle relaxants, and muscle relaxant antagonists administered in conjunction with general anesthesia. It also has been administered in outpatient settings, both in trials in conscious sedation and in the emergency management of overdose following a wide variety of agents. No deleterious interactions have been observed. Preclinical studies have shown that both flumazenil and nalmefene can induce seizures in animals. The coadministration of both flumazenil and nalmefene produced fewer seizures than expected in a study in rodents, based on the expected effects of each drug alone. Based on these data, an adverse interaction from the coadministration of the two drugs is not expected, but physicians should remain aware of the potential risk of seizures from agents in these classes.

ADVERSE REACTIONS The following serious adverse reactions are discussed elsewhere in the labeling: Recurrent Respiratory and Central Nervous System Depression [see Warnings and Precautions (5.1) ] Precipitation of Severe Opioid Withdrawal [see Warnings and Precautions (5.3) ] Most common adverse reactions (incidence at least 2%) are nasal discomfort, headache, nausea, dizziness, hot flush, vomiting, anxiety, fatigue, nasal congestion, throat irritation, rhinalgia, decreased appetite, dysgeusia, erythema, and hyperhidrosis. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Indivior Inc. at 1-877-782-6966 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to the rates in clinical trials of another drug and may not reflect the rates observed in practice. The safety of OPVEE nasal spray is supported by safety and pharmacokinetic studies of OPVEE nasal spray in healthy subjects in a normal state and under steady state opioid agonism. The following adverse reactions were observed. In a pharmacokinetic study of 66 healthy adult volunteers exposed to one spray of OPVEE nasal spray in one nostril the most common adverse reactions were: nasal discomfort and dizziness. In a second pharmacokinetic study of 24 healthy adult volunteers exposed to one spray of OPVEE nasal spray in one nostril, two sprays of OPVEE nasal spray in one nostril or one spray of OPVEE nasal spray in each nostril, the most common adverse reactions were: rhinalgia, nasal congestion, nasal discomfort and nausea. In a pharmacodynamic study of 61 healthy adult volunteers exposed to one spray of OPVEE nasal spray in one nostril, the most common adverse reactions were: headache, nausea, hot flush and dizziness. Table 1: Relative Frequencies of Treatment-Related Common Adverse Events That Occurred in Greater Than 1% of Healthy Adult Volunteers Nalmefene 2.7 mg Nalmefene 5.4 mg System Organ Class Preferred Term Total 2.7 mg N=150 n (%) PD Study N=61 n (%) PK Studies N=89 n (%) PK Study (1 spray in each nostril) N=23 n (%) PK Study (2 sprays in one nostril) N=24 n (%) PK Studies OPNT003-PK-001 + OPNT003-PK-002 and PD Study OPNT003-OOD-001 Respiratory, thoracic and mediastinal disorders Nasal discomfort 43 (28.7%) 5 (8.2%) 38 (42.7%) 3 (13.0%) 3 (12.5%) Nasal congestion 6 (4.0%) 2 (3.3%) 4 (4.5%) 1 (4.3%) 4 (16.7%) Throat irritation 6 (4.0%) 3 (4.9%) 3 (3.4%) 0 0 Rhinalgia 4 (2.7%) 1 (1.6%) 3 (3.4%) 2 (8.7%) 6 (25.0%) Dyspnea 2 (1.3%) 2 (3.3%) 0 0 0 Oropharyngeal pain 2 (1.3%) 2 (3.3%) 0 1 (4.3%) 1 (4.2%) Nervous system disorders Headache 40 (26.7%) 34 (55.7%) 6 (6.7%) 1 (4.3%) 0 Dizziness 14 (9.3%) 9 (14.8%) 5 (5.6%) 0 1 (4.2%) Dysgeusia 3 (2.0%) 2 (3.3%) 1 (1.1%) 0 0 Paresthesia 2 (1.3%) 2 (3.3%) 0 1 (4.3%) 1 (4.2%) Presyncope 0 0 0 1 (4.3%) 0 Gastrointestinal disorders Nausea 25 (16.7%) 22 (36.1%) 3 (3.4%) 5 (21.7%) 1 (4.2%) Vomiting 9 (6.0%) 7 (11.5%) 2 (2.2%) 1 (4.3%) 0 Abdominal pain 2 (1.3%) 1 (1.6%) 1 (1.1%) 0 0 Dry mouth 1 (0.7%) 1 (1.6%) 0 1 (4.3%) 0 Constipation 0 0 0 0 1 (4.2%) Vascular disorders Hot flush 12 (8.0%) 12 (19.7%) 0 0 0 Psychiatric disorders Anxiety 7 (4.7%) 7 (11.5%) 0 0 0 Agitation 2 (1.3%) 2 (3.3%) 0 0 0 Claustrophobia 2 (1.3%) 2 (3.3%) 0 0 0 Insomnia 1 (0.7%) 0 1 (1.1%) 1 (4.3%) 0 General disorders and administration site conditions Fatigue 6 (4.0%) 3 (4.9%) 3 (3.4%) 0 0 Chills 2 (1.3%) 2 (3.3%) 0 0 0 Chest discomfort 0 0 0 1 (4.3%) 0 Skin and subcutaneous tissue disorders Erythema 3 (2.0%) 0 3 (3.4%) 1 (4.3%) 1 (4.2%) Hyperhidrosis 3 (2.0%) 3 (6.6%) 0 0 1 (4.2%) Urticaria 0 0 0 0 1 (4.2%) Metabolism and nutrition disorders Decreased appetite 3 (2.0%) 2 (3.3%) 1 (1.1%) 0 0 Infections and infestations Rhinitis 1 (0.7%) 0 1 (1.1%) 1 (4.3%) 0 Eye disorders Dry eye 0 0 0 1 (4.3%) 0 Cardiac disorders Tachycardia 0 0 0 1 (4.3%) 0 Adverse reaction information was obtained following administration of nalmefene injection to 152 normal volunteers and in controlled clinical trials to 1127 patients for the treatment of opioid overdose or for postoperative opioid reversal. Table 2. Relative Frequencies of Common Adverse Reactions with an Incidence Greater than 1% (all patients, all clinical settings) Adverse Reaction Nalmefene Placebo N=1127 N=77 Nausea 18% 6% Vomiting 9% 4% Tachycardia 5% - Hypertension 5% - Postoperative Pain 4% N/A Fever 3% - Dizziness 3% 1% Headache 1% 4% Chills 1% - Hypotension 1% - Vasodilatation 1% - Incidence less than 1% Cardiovascular : Bradycardia, arrhythmia Digestive : Diarrhea, dry mouth Nervous System : Somnolence, depression, agitation, nervousness, tremor, confusion, withdrawal syndrome, myoclonus Respiratory : Pharyngitis Skin : Pruritus Urogenital : Urinary retention The incidence of adverse events was highest in patients who received more than the recommended dose of nalmefene injection. 6.2 Postmarketing Experience The following adverse reactions have been identified during post-approval use of nalmefene. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Abrupt reversal of opioid depression using nalmefene in both postoperative and emergency department settings has resulted in nausea, vomiting, sweating, tremulousness, seizures, and cardiovascular instability including tachycardia, hypotension, hypertension, ventricular tachycardia and fibrillation, pulmonary edema, and cardiac arrest. Death, coma, and encephalopathy have been reported as sequelae of these events. These events have primarily occurred in patients who had pre-existing cardiovascular disorders or received other drugs that may have similar adverse cardiovascular effects. In persons who were physically dependent on opioids, abrupt reversal of opioid effects has precipitated an acute withdrawal syndrome. Signs and symptoms have included: body aches, fever, sweating, runny nose, sneezing, piloerection, yawning, weakness, shiver or trembling, nervousness, restlessness or irritability, diarrhea, nausea or vomiting, abdominal cramps, increased blood pressure, tachycardia. In some patients, there may be aggressive behavior upon abrupt reversal of an opioid overdose. In the neonate, opioid withdrawal symptoms also included convulsions, excessive crying, and hyperactive reflexes.

CLINICAL PHARMACOLOGY Pharmacodynamics Nalmefene hydrochloride injection prevents or reverses the effects of opioids, including respiratory depression, sedation, and hypotension. Pharmacodynamic studies have shown that nalmefene hydrochloride injection has a longer duration of action than naloxone at fully reversing doses. Nalmefene hydrochloride injection has no opioid agonist activity. Nalmefene hydrochloride injection is not known to produce respiratory depression, psychotomimetic effects, or pupillary constriction. No pharmacological activity was observed when nalmefene hydrochloride injection was administered in the absence of opioid agonists. Nalmefene hydrochloride injection has not been shown to produce tolerance, physical dependence, or abuse potential. Nalmefene hydrochloride injection 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 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 to 32 62 to 80 C p at 5 min. (ng/mL) 3.7 (29) 5.8 (38) V dss (L/kg) 8.6 (19) 8.6 (29) V c (L/kg) 3.9 (29) 2.8 (41) AUC 0-inf (ng-hr/mL) 16.6 (27) 17.3 (14) Terminal T 1/2 (hr) 10.8 (48) 9.4 (49) Cl plasma (L/hr/kg) 0.8 (23) 0.8 (18) ABSORPTION 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 to 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. DISTRIBUTION Following a 1 mg parenteral dose, nalmefene was rapidly distributed. In a study of brain receptor occupancy, a 1 mg dose of nalmefene blocked over 80% of brain opioid receptors within 5 minutes after administration. The apparent volumes of distribution centrally (V c ) and at steady-state (V dss ) are 3.9 ± 1.1 L/kg and 8.6 ± 1.7 L/kg, respectively. Ultrafiltration studies of nalmefene have demonstrated that 45% (CV 4.1%) is bound to plasma proteins over a concentration range of 0.1 to 2 mcg/mL. An in vitro determination of the distribution of nalmefene in human blood demonstrated that nalmefene distributed 67% (CV 8.7%) into red blood cells and 39% (CV 6.4%) into plasma. The whole blood to plasma ratio was 1.3 (CV 6.6%) over the nominal concentration range in whole blood from 0.376 to 30 ng/mL. METABOLISM Nalmefene is metabolized by the liver, primarily by glucuronide conjugation, and excreted in the urine. Nalmefene is also metabolized to trace amounts of an N-dealkylated metabolite. Nalmefene glucuronide is inactive and the N-dealkylated metabolite has minimal pharmacological activity. Less than 5% of nalmefene is excreted in the urine unchanged. Seventeen percent (17%) of the nalmefene dose is excreted in the feces. The plasma concentration-time profile in some subjects suggests that nalmefene undergoes enterohepatic recycling. ELIMINATION After intravenous administration of 1 mg nalmefene hydrochloride injection to normal males (ages 19 to 32), plasma concentrations declined biexponentially with a redistribution and a terminal elimination half-life of 41 ± 34 minutes and 10.8 ± 5.2 hours, respectively. The systemic clearance of nalmefene is 0.8 ± 0.2 L/hr/kg and the renal clearance is 0.08 ± 0.04 L/hr/kg. Special Populations ELDERLY Dose proportionality was observed in nalmefene AUC 0-inf following 0.5 to 2 mg intravenous administration to elderly male subjects. Following a 1 mg intravenous nalmefene dose, there were no significant differences between young (19 to 32 years) and elderly (62 to 80 years) adult male subjects with respect to plasma clearance, steady-state volume of distribution, or half-life. There was an apparent age-related decrease in the central volume of distribution (young: 3.9 ± 1.1 L/kg, elderly: 2.8 ± 1.1 L/kg) that resulted in a greater initial nalmefene concentration in the elderly group. While initial nalmefene plasma concentrations were transiently higher in the elderly, it would not be anticipated that this population would require dosing adjustment. No clinical adverse events were noted in the elderly following the 1 mg intravenous nalmefene dose. PATIENTS WITH HEPATIC IMPAIRMENT Subjects with hepatic disease, when compared to matched normal controls, had a 28.3% decrease in plasma clearance of nalmefene (0.56 ± 0.21 L/hr/kg versus 0.78 ± 0.24 L/hr/kg, respectively). Elimination half-life increased from 10.2 ± 2.2 hours to 11.9 ± 2.0 hours in the hepatically impaired. No dosage adjustment is recommended since nalmefene will be administered as an acute course of therapy. PATIENTS WITH RENAL IMPAIRMENT There was a statistically significant 27% decrease in plasma clearance of nalmefene in the end-stage renal disease (ESRD) population during interdialysis (0.57 ± 0.20 L/hr/kg) and a 25% decreased plasma clearance in the ESRD population during intradialysis (0.59 ± 0.18 L/hr/kg) compared to normal patients (0.79 ± 0.24 L/hr/kg). The elimination half-life was prolonged in ESRD patients from 10.2 ± 2.2 hours in normal patients to 26.1 ± 9.9 hours (see DOSAGE AND ADMINISTRATION ). GENDER DIFFERENCES There has not been sufficient pharmacokinetic study to make a definitive statement as to whether the pharmacokinetics of nalmefene differs between the genders.