NALMEFENE: 197 Adverse Event Reports & Safety Profile

Nalmefene Hydrochloride Injection Rx only DESCRIPTION Nalmefene Hydrochloride Injection, an opioid antagonist, is a 6-methylene analogue of naltrexone. The chemical structure is shown below: Molecular Formula: C 21 H 25 NO 3

• HCl•H 2 O Molecular Weight: 393.91, CAS # 1228646-72-7 Chemical Name: 17-(Cyclopropylmethyl)-4,5α-epoxy-6-methylenemorphinan-3,14-diol, hydrochloride salt, monohydrate Nalmefene hydrochloride is a white to almost white crystalline powder which is freely soluble in water up to 130 mg/mL and slightly soluble in chloroform up to 0.13 mg/mL, with a pK a of 7.6.

Nalmefene Hydrochloride

Injection is available as a sterile solution for intravenous, intramuscular, and subcutaneous administration in two concentrations, containing 100 µg or 1.0 mg of nalmefene free base per mL.

The

100 µg/mL concentration contains 110.8 µg of nalmefene hydrochloride and the 1.0 mg/mL concentration contains 1.108 mg of nalmefene hydrochloride per mL. Both concentrations contain 9.0 mg of sodium chloride per mL and the pH is adjusted in the range of 3.3-3.5 with hydrochloric acid. Concentrations and dosages of Nalmefene Hydrochloride Injection are expressed as the free base equivalent of nalmefene. image description

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 .)

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 )

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.

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 <span class="opacity-50 text-xs">[see Dosage and Administration (2.2) ]</span>.

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 <span class="opacity-50 text-xs">[see Dosage and Administration (2.3) ]</span> . 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. <span class="opacity-50 text-xs">[see Use in Specific Populations (8.4) ]</span> .

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.

PRECAUTIONS General CARDIOVASCULAR RISKS WITH NARCOTIC ANTAGONISTS Pulmonary edema, cardiovascular instability, hypotension, hypertension, ventricular tachycardia, and ventricular fibrillation have been reported in connection with opioid reversal in both postoperative and emergency department settings. In many cases, these effects appear to be the result of abrupt reversal of opioid effects. Although nalmefene hydrochloride injection has been used safely in patients with pre-existing cardiac disease, all drugs of this class should be used with caution in patients at high cardiovascular risk or who have received potentially cardiotoxic drugs. (See DOSAGE AND ADMINISTRATION .)

Risk Of Precipitated Withdrawal

Nalmefene hydrochloride injection, like other opioid antagonists, is known to produce acute withdrawal symptoms and, therefore, should be used with extreme caution in patients with known physical dependence on opioids or following surgery involving high doses of opioids. Imprudent use or excessive doses of opioid antagonists in the postoperative setting has been associated with hypertension, tachycardia, and excessive mortality in patients at high risk for cardiovascular complications. (See PRECAUTIONS .)

Incomplete Reversal Of Buprenorphine

Preclinical studies have shown that nalmefene at doses up to 10 mg/kg (437 times the maximum recommended human dose) produced incomplete reversal of buprenorphine- induced analgesia in animal models. This appears to be a consequence of a high affinity and slow displacement of buprenorphine from the opioid receptors. Hence, nalmefene hydrochloride injection may not completely reverse buprenorphine-induced respiratory depression.

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. Carcinogenesis, Mutagenesis, Impairment of Fertility Nalmefene did not have mutagenic activity in the Ames test with five bacterial strains or the mouse lymphoma assay. Clastogenic activity was not observed in the mouse micronucleus test or in the cytogenic bone marrow assay in rats. However, nalmefene did exhibit a weak but significant clastogenic activity in the human lymphocyte metaphase assay in the absence but not in the presence of exogenous metabolic activation. Oral administration of nalmefene up to 1200 mg/m 2 /day did not affect fertility, reproductive performance, and offspring survival in rats. Use in Pregnancy Reproduction studies have been performed in rats (up to 1200 mg/m 2 /day) and rabbits (up to 2400 mg/m 2 /day) by oral administration of nalmefene and in rabbits by intravenous administration up to 96 mg/m 2 /day (114 times the human dose). There was no evidence of impaired fertility or harm to the fetus. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Nursing Mothers

Nalmefene and its metabolites were secreted into rat milk, reaching concentrations approximately three times those in plasma at one hour and decreasing to about half the corresponding plasma concentrations by 24 hours following bolus administration. As no clinical information is available, caution should be exercised when Nalmefene Hydrochloride Injection is administered to a nursing woman. Use in Pediatric Patients Safety and effectiveness of nalmefene hydrochloride injection in pediatric patients have not been established. Use in Neonates The safety and effectiveness of nalmefene hydrochloride injection in neonates have not been established in clinical studies. In a preclinical study, nalmefene was administered by subcutaneous injection to rat pups at doses up to 205 mg/m 2 /day throughout maternal lactation without producing adverse effects. A preclinical study evaluating the irritancy of the dosage form following arterial and venous administration in animals showed no vascular irritancy.

Nalmefene Hydrochloride

Injection should only be used in the resuscitation of the newborn when, in the opinion of the treating physician, the expected benefits outweigh the risks.

Geriatric Use

Clinical studies of nalmefene hydrochloride injection did not include sufficient number of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

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.