DEMEROL

DEMEROL (meperidine hydrochloride injection) is an opioid agonist available as a sterile aqueous solution, for intramuscular, intravenous, or subcutaneous administration. It contains meperidine hydrochloride as the active pharmaceutical ingredient. Meperidine hydrochloride chemical name is 4‑Piperidinecarboxylic acid, 1‑methyl-4-phenyl-,ethyl ester, hydrochloride. The molecular weight is 283.79 g/mol. Its molecular formula is C 15 H 21 NO 2 ·HCl, and it has the following chemical structure. Meperidine hydrochloride is a white crystalline substance with a melting point of 186° C to 189° C, and it is readily soluble in water. DEMEROL (meperidine hydrochloride injection) is available as: Single-dose Carpuject TM cartridge with Luer Lock for the Carpuject Syringe System: 25 mg/mL, 50 mg/mL, 75 mg/mL, and 100 mg/mL. Each mL of Single-dose cartridge contains 25 mg, 50 mg, 75 mg or 100 mg of meperidine hydrochloride USP (equivalent to 21.79 mg, 43.58 mg, 65.36 mg or 87.15 mg of meperidine), respectively, and sodium hydroxide NF, and hydrochloric acid NF as pH adjusters, in water for injection. Only the 25 mg strength contains 3.8 mg of sodium chloride USP as isotonicity agent. Multiple-dose vials: 1,500 mg/30 mL (50 mg/mL) strength. Each mL of vial contains 50 mg of meperidine hydrochloride USP (equivalent to 43.58 mg of meperidine), 1 mg of meta-cresol USP, as a preservative, and sodium hydroxide NF, and hydrochloric acid NF as pH adjusters, in water for injection. Single-dose NexJect™ Prefilled Syringe with Luer Lock: 25 mg/mL and 50 mg/mL strengths. Each mL contains 25 mg or 50 mg of meperidine hydrochloride USP (equivalent to 21.79 mg or 43.58 mg of meperidine), respectively, and sodium hydroxide NF, and hydrochloric acid NF as pH adjusters, in water for injection. Only the 25 mg strength contains 3.8 mg of sodium chloride USP as isotonicity agent. The pH of DEMEROL (meperidine hydrochloride injection) solutions is between 3.5 and 6.0. DEMEROL (meperidine hydrochloride injection) 5 percent solution has a specific gravity of 1.0086 at 20°C, and the 10 percent solution has a specific gravity of 1.0165 at 20°C. Chemical Structure

DEMEROL Injection is indicated for preoperative medication, support of anesthesia, and obstetrical analgesia. DEMEROL Injection is indicated for the management of pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate. DEMEROL Injection is indicated for preoperative medication, support of anesthesia, for obstetrical analgesia, and for the management of pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate. ( 1 ) Limitations of Use Because of the risks of addiction, abuse, misuse, overdose, and death, which can occur at any dosage or duration and persist over the course of therapy, reserve opioid analgesics, including DEMEROL Injection, for use in patients for whom alternative treatment options are ineffective, not tolerated, or would be otherwise inadequate to provide sufficient management of pain. Use of ‎DEMEROL Injection for an extended period of time may increase the risk of ‎toxicity (e.g., seizures) from the accumulation of the meperidine metabolite, ‎normeperidine. ( 1 , 5.1 )‎ Limitations of Use: Because of the risks of addiction, abuse, misuse , overdose, and death , which can occur at any dosage or duration and persist over the course of therapy, [see Warnings and Precautions (5.1) ] , reserve opioid analgesics, including DEMEROL Injection, for use in patients for whom alternative treatment options are ineffective, not tolerated, or would be otherwise inadequate to provide sufficient management of pain. Use of DEMEROL Injection for an extended period of time may increase the risk of toxicity (e.g., seizures) from the accumulation of the meperidine metabolite, normeperidine.

• DEMEROL Injection should be prescribed only by healthcare ‎professionals who are knowledgeable about the use of ‎opioids and how to mitigate the associated risks. ( 2.1 )‎ • Use the lowest effective dosage for the shortest duration of time consistent with individual patient treatment goals. ‎Reserve titration to higher doses of DEMEROL ‎Injection for patients in whom lower doses are ‎insufficiently effective and in whom the expected benefits ‎of using a higher dose opioid clearly outweigh the ‎substantial risks. ( 2.1 , 5 )‎ • Many acute pain conditions (e.g., the pain that occurs with ‎a number of surgical procedures or acute ‎musculoskeletal injuries) require no more than a few ‎days of an opioid analgesic. Clinical guidelines on ‎opioid prescribing for some acute pain conditions are ‎available. ( 2.1 )‎ • Initiate the dosing regimen for each patient individually, ‎taking into account the patient’s underlying cause and ‎severity of pain, prior analgesic treatment and ‎response, and risk factors for addiction, abuse, and ‎misuse. ( 2.1 , 5.2 )‎ • Respiratory depression can occur at any time during opioid ‎therapy, especially when initiating and following dosage ‎increases with DEMEROL Injection. Consider this risk ‎when selecting an initial dose and when making dose ‎adjustments. ( 2.2 , 5.3 )‎ • Periodically reassess patients receiving DEMEROL Injection to evaluate the continued need for opioid analgesics to maintain pain control, for the signs or symptoms of adverse reactions, and for the development of addiction, abuse, or misuse. ( 2.2 ) • For Relief of Pain: Titrate the dose based upon the individual patient’s response to their ‎initial dose of DEMEROL Injection. ( 2.2 , 5 )‎ Adults: 50 mg to 150 mg intramuscularly or subcutaneously every 3 to 4 hours. ( 2.2 ) Children: 0.5 mg/lb to 0.8 mg/lb intramuscularly or subcutaneously up to the adult dose every 3 to 4 hours. ( 2.2 ) • Preoperative Medication: Adults: 50 mg to 100 mg intramuscularly or subcutaneously, 30 to 90 minutes before beginning anesthesia. ( 2.3 ) Children: 0.5 mg/lb to 1 mg/lb intramuscularly or subcutaneously up to the adult dose, 30 to 90 minutes before beginning anesthesia. ( 2.3 ) • Obstetrical Analgesia: 50 mg to 100 mg intramuscularly or subcutaneously; may be repeated at 1 to 3 hour intervals. ( 2.4 ) • Do not rapidly reduce or abruptly discontinue DEMEROL Injection in a physically‑dependent patient. ( 2.2 , 5.15 ) 2.1 Important Dosage and Administration Instructions • DEMEROL Injection should be prescribed only by healthcare professionals ‎who are knowledgeable about the use of opioids and how to mitigate the ‎associated risks.‎ • Use the lowest effective dosage for the shortest duration of time consistent with individual patient treatment goals [see Warnings and Precautions (5) ]. Because the risk of overdose increases as opioid doses increase, reserve ‎titration to higher doses of DEMEROL Injection for patients in whom lower ‎doses are insufficiently effective and in whom the expected benefits of using a ‎higher dose opioid clearly outweigh the substantial risks.‎ • Many acute pain conditions (e.g., the pain that occurs with a number of surgical ‎procedures or acute musculoskeletal injuries) require no more than a few days of ‎an opioid analgesic. Clinical guidelines on opioid prescribing for some acute ‎pain conditions are available.‎ • There is variability in the opioid analgesic dose and duration needed to ‎adequately manage pain due both to the cause of pain and to individual patient ‎factors. ‎Initiate the dosing regimen for each patient individually, taking into account the patient's underlying cause and severity of pain, prior analgesic treatment and response, and risk factors for addiction, abuse, and misuse [see Warnings and Precautions (5.1) ] . • Respiratory depression can occur at any time during opioid therapy, especially ‎when initiating and following dosage increases with DEMEROL Injection.‎ Consider this risk when selecting an initial dose and when making dose ‎adjustments [see Warnings and Precautions (5) ] . • Inspect DEMEROL Injection for particulate matter and discoloration prior to administration. Do not use if color is darker than pale yellow, if it is discolored in any other way, or if it contains a ‎precipitate.‎ 2.2 For Management of Pain Initial Dosage Dosage should be adjusted according to the severity of the pain and the response of the patient. While subcutaneous administration is suitable for occasional use, intramuscular administration is preferred when repeated doses are required. If intravenous administration is required, dosage should be decreased and the injection made very slowly, preferably utilizing a diluted solution. Adults: Initiate treatment in a dosing range of 50 mg to 150 mg intramuscularly or subcutaneously every 3 to 4 hours as needed for pain, and at the lowest dose necessary to achieve adequate analgesia. Elderly patients should usually be given meperidine at the lower end of the dose range and observed closely. Children: Initiate treatment in a dosing range of 0.5 mg/lb to 0.8 mg/lb intramuscularly or subcutaneously up to the adult dose, every 3 to 4 hours as necessary, and at the lowest dose necessary to achieve adequate analgesia. Titration and Maintenance of Therapy Titrate the dose based upon the individual patient’s response to their initial dose of DEMEROL Injection. Individually titrate DEMEROL Injection to a dose that provides adequate analgesia and minimizes adverse reactions. Continually reevaluate patients receiving DEMEROL Injection to assess the maintenance of pain control, signs and symptoms of opioid withdrawal, and other adverse reactions, as well as to reassess for the development of addiction, abuse, or misuse [see Warnings and Precautions (5.1 , 5.15) ] . Frequent communication is important among the prescriber, other members of the health and care team, the patient, and the caregiver/family during periods of changing analgesic requirements, including initial titration. If the level of pain increases after dosage stabilization, attempt to identify the source of increased pain before increasing the DEMEROL Injection dosage. If after increasing the dosage, unacceptable opioid-related adverse reactions are observed (including an increase in pain after a dosage increase), consider reducing the dosage [see Warnings and Precautions ‎‎(5) ] . Adjust the dosage to obtain an appropriate balance between management of pain and opioid-related adverse reactions. Discontinuation of DEMEROL Injection When a patient who has been taking DEMEROL Injection regularly and may be physically-dependent no longer requires therapy with DEMEROL Injection, taper the dose gradually, by 25% to 50% every 2 to 4 days, while monitoring carefully for signs and symptoms of withdrawal. If the patient develops these signs or symptoms, raise the dose to the previous level and taper more slowly, either by increasing the interval between decreases, decreasing the amount of change in dose, or both. Do not rapidly reduce or abruptly discontinue DEMEROL Injection in patient s who may be physically dependent on opioids [see Warnings and Precautions (5.15) , Drug Abuse and Dependence (9.3) ] . 2.3 For Preoperative Medication Adults: The usual dosage is 50 mg to 100 mg intramuscularly or subcutaneously, 30 to 90 minutes before the beginning of anesthesia. Elderly patients should usually be given meperidine at the lower end of the dose range and observed closely. Children: The usual dosage is 0.5 mg/lb to 1 mg/lb intramuscularly or subcutaneously up to the adult dose, 30 to 90 minutes before the beginning of anesthesia. 2.4 For Support of Anesthesia Repeated slow intravenous Injections of fractional doses (e.g., 10 mg/mL) or continuous intravenous infusion of a more dilute solution (e.g., 1 mg/mL) should be used. The dose should be titrated to the needs of the patient and will depend on the premedication and type of anesthesia being employed, the characteristics of the particular patient, and the nature and duration of the operative procedure. Elderly patients should usually be given meperidine at the lower end of the dose range and observed closely. 2.5 For Obstetrical Analgesia The usual dosage is 50 mg to 100 mg intramuscularly or subcutaneously when pain becomes regular, and may be repeated at 1- to 3-hour intervals. 2.6 Dosage Modifications with Concomitant Phenothiazines The dose of DEMEROL Injection should be proportionately reduced (usually by 25 to 50 percent) when administered concomitantly with phenothiazines and many other tranquilizers since they potentiate the action of DEMEROL Injection.

DEMEROL Injection is contraindicated in patients with: • Significant respiratory depression [see Warnings and Precautions (5.2) ] • Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment [see Warnings and Precautions (5.9) ] • Concurrent use of monoamine oxidase inhibitors (MAOIs) or use of MAOIs within the last 14 days [see Warnings and Precautions (5.6) , Drug Interactions (7) ] • Known or suspected gastrointestinal obstruction, including paralytic ileus [see Warnings and Precautions (5.13) ] • Hypersensitivity to meperidine (e.g., anaphylaxis) [see Adverse Reactions (6) ] • Significant respiratory depression. ( 4 ) • Acute or severe bronchial asthma in an unmonitored setting or in absence of resuscitative equipment. ( 4 ) • Concurrent use of monoamine oxidase inhibitors (MAOIs) or use of MAOIs within the last 14 days. ( 7 ) • Known or suspected gastrointestinal obstruction, including paralytic ileus. ( 4 ) • Hypersensitivity to meperidine or to any other ingredients of the product. ( 4 )

The following serious adverse reactions are described, or described in greater detail, in other sections: • Addiction, Abuse, and Misuse [see Warnings and Precautions (5.1) ] • Life-Threatening Respiratory Depression [see Warnings and Precautions (5.2) ] • Interactions with Benzodiazepines or Other CNS Depressants [see Warnings and Precautions (5.3) ] • Neonatal Opioid Withdrawal Syndrome [see Warnings and Precautions (5.4) ] • Opioid-Induced Hyperalgesia and Allodynia [see Warnings and Precautions (5.7) ]‎ • Serotonin Syndrome with Concomitant Use of Serotonergic Drugs [see Warnings and Precautions (5.8) ] • Adrenal Insufficiency [see Warnings and Precautions (5.10) ] • Severe Hypotension [see Warnings and Precautions (5.11) ] • Gastrointestinal Adverse Reactions [see Warnings and Precautions (5.13) ] • Seizures [see Warnings and Precautions (5.14) ] • Withdrawal [see Warnings and Precautions (5.15) ] The following adverse reactions associated with the use of meperidine were identified in clinical studies or postmarketing reports. Because some of these reactions were 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. The major hazards of meperidine, as with other opioid analgesics, are respiratory depression and, to a lesser degree, circulatory depression; respiratory arrest, shock, and cardiac arrest have occurred. The most frequently observed adverse reactions include lightheadedness, dizziness, sedation, nausea, vomiting, and sweating. These effects seem to be more prominent in ambulatory patients and in those who are not experiencing severe pain. In such individuals, lower doses are advisable. Some adverse reactions in ambulatory patients may be alleviated if the patient lies down. Other adverse reactions include: Nervous System : Mood changes (e.g., euphoria, dysphoria), weakness, headache, agitation, tremor, involuntary muscle movements (e.g., muscle twitches, myoclonus), severe convulsions, seizures, transient hallucinations and disorientation, confusion, delirium, visual disturbances. Inadvertent injection about a nerve trunk may result in sensory-motor paralysis which is usually, though not always, transitory. Gastrointestinal : Dry mouth, constipation, biliary tract spasm. Cardiovascular : Flushing of the face, tachycardia, bradycardia, palpitation, hypotension [see Warnings and Precautions (5.18) ] , syncope, phlebitis following intravenous injection. Genitourinary : Urinary retention. Allergic : Pruritus, urticaria, other skin rashes, wheal and flare over the vein with intravenous injection. Hypersensitivity reactions, anaphylaxis. Histamine release leading to hypotension and/or tachycardia, flushing, sweating, and pruritus. Other : Pain at injection site; local tissue irritation and induration following subcutaneous injection, particularly when repeated; antidiuretic effect. Serotonin syndrome : Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of opioids with serotonergic drugs. Adrenal insufficiency : Cases of adrenal insufficiency have been reported with opioid use, more often following greater than one month of use. Androgen deficiency : Cases of androgen deficiency have occurred with use of opioids for an extended period of time [see Clinical Pharmacology (12.2) ] . Hyperalgesia and Allodynia : Cases of hyperalgesia and allodynia have been ‎reported with opioid therapy of any duration [see Warnings and Precautions ‎‎(5.7) ]‎. Hypoglycemia : Cases of hypoglycemia have been reported in patients ‎taking opioids. Most reports were in patients with at least one ‎predisposing risk factor (e.g., diabetes).‎ Opioid-induced esophageal dysfunction (OIED) : Cases of OIED have been reported in patients taking opioids and may occur more frequently in patients taking higher doses of opioids, and/or in patients taking opioids longer term [see Warnings and Precautions (5.13) ]. Adverse Reactions from Observational Studies A prospective, observational cohort study estimated the risks of addiction, abuse, and misuse in patients initiating long-term use of Schedule II opioid analgesics between 2017 and 2021. Study participants included in one or more analyses had been enrolled in selected insurance plans or health systems for at least one year, were free of at least one outcome at baseline, completed a minimum number of follow-up assessments, and either: 1) filled multiple extended-release/long-acting opioid analgesic prescriptions during a 90‑day period (n=978); or 2) filled any Schedule II opioid analgesic prescriptions covering at least 70 of 90 days (n=1,244). Those included also had no dispensing of the qualifying opioids in the previous 6 months. Over 12 months: • approximately 1% to 6% of participants across the two cohorts newly met criteria for addiction, as assessed with two validated interview-based measures of moderate-to-severe opioid use disorder based on Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, and • approximately 9% and 22% of participants across the two cohorts newly met criteria for prescription opioid abuse and misuse [defined in Drug Abuse and Dependence (9.2) ] , respectively, as measured with a validated self-reported instrument. A retrospective, observational cohort study estimated the risk of opioid-involved overdose or opioid overdose-related death in patients with new long-term use of Schedule II opioid analgesics from 2006 through 2016 (n=220,249). Included patients had been enrolled in either one of two commercial insurance programs, one managed care program, or one Medicaid program for at least 9 months. New long-term use was defined as having Schedule II opioid analgesic prescriptions covering at least 70 days’ supply over the 3 months prior to study entry and none during the preceding 6 months. Patients were excluded if they had an opioid-involved overdose in the 9 months prior to study entry. Overdose was measured using a validated medical code-based algorithm with linkage to the National Death Index database. The 5-year cumulative incidence estimates for opioid-involved overdose or opioid overdose-related death ranged from approximately 1.5% to 4% across study sites, counting only the first event during follow-up. Approximately 17% of first opioid overdoses observed over the entire study period (5-11 years, depending on the study site) were fatal. Higher baseline opioid dose was the strongest and most consistent predictor of opioid-involved overdose or opioid overdose-related death. Study exclusion criteria may have selected patients at lower risk of overdose, and substantial loss to follow-up (approximately 80%) also may have biased estimates. The risk estimates from the studies described above may not be generalizable to all patients receiving opioid analgesics, such as those with exposures shorter or longer than the duration evaluated in the studies. Most common adverse reactions were lightheadedness, dizziness, sedation, nausea, vomiting and sweating. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Pfizer, Inc. at 1-800-438-1985, or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

Table 1 includes clinically significant drug interactions with DEMEROL Injection. Table 1: Clinically Significant Drug Interactions with DEMEROL Injection Monoamine Oxidase Inhibitors (MAOIs) Clinical Impact: Meperidine is contraindicated in patients who are receiving monoamine oxidase (MAO) inhibitors or those who have recently received such agents. Therapeutic doses of meperidine have occasionally precipitated unpredictable, severe, and occasionally fatal reactions in patients who have received such agents within 14 days. The mechanism of these reactions is unclear but may be related to a preexisting hyperphenylalaninemia. Some have been characterized by coma, severe respiratory depression, cyanosis, and hypotension, and have resembled the syndrome of acute opioid overdose. Serotonin syndrome with agitation, hyperthermia, diarrhea, tachycardia, sweating, tremors, and impaired consciousness may also occur. In other reactions the predominant manifestations have been hyperexcitability, convulsions, tachycardia, hyperpyrexia, and hypertension [see Warnings and Precautions (5.6) ]‎ . Intervention: Do not use DEMEROL Injection in patients taking MAOIs or within 14 days of stopping such treatment. Intravenous hydrocortisone or prednisolone have been used to treat severe reactions, with the addition of intravenous chlorpromazine in those cases exhibiting hypertension and hyperpyrexia. The usefulness and safety of opioid overdose reversal agents in the treatment of these reactions are unknown. Examples: Phenelzine, tranylcypromine, linezolid Inhibitors of CYP3A4 and CYP2B6 Clinical Impact: The concomitant use of DEMEROL Injection and CYP3A4 or CYP2B6 inhibitors can increase the plasma concentration of meperidine, resulting in increased or prolonged opioid effects. These effects could be more pronounced with concomitant use of DEMEROL Injection and CYP2B6 and CYP3A4 inhibitors, particularly when an inhibitor is added after a stable dose of DEMEROL Injection is achieved [see Warnings and Precautions (5.5) ] . After stopping a CYP3A4 inhibitor, as the effects of the inhibitor decline, the meperidine plasma concentration will decrease [see Clinical Pharmacology (12.3) ] , potentially resulting in decreased opioid efficacy or a withdrawal syndrome in patients who had developed physical dependence to meperidine. Intervention: If concomitant use is necessary, consider dosage reduction of DEMEROL Injection until stable drug effects are achieved. Monitor patients for respiratory depression and sedation at frequent intervals. If a CYP3A4 or CYP2B6 inhibitor is discontinued, consider increasing the DEMEROL Injection dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal. Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconizole), protease inhibitors (e.g., ritonavir) CYP3A4 and CYP2B6 Inducers Clinical Impact: The concomitant use of DEMEROL Injection and CYP3A4 inducers or CYP2B6 inducers can decrease the plasma concentration of meperidine [see Clinical Pharmacology (12.3) ] , resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence to meperidine [see Warnings and Precautions (5.5) ] . After stopping a CYP3A4 or CYP2B6 inducer, as the effects of the inducer decline, the meperidine plasma concentration will increase [see Clinical Pharmacology (12.3) ] , which could increase or prolong both the therapeutic effects and adverse reactions and may cause serious respiratory depression. Intervention: If concomitant use is necessary, consider increasing the DEMEROL Injection dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal. If a CYP3A4 or CYP2B6 inducer is discontinued, consider DEMEROL Injection dosage reduction and monitor for signs of respiratory depression. Examples: Rifampin, carbamazepine, phenytoin Benzodiazepines and Other Central Nervous System (CNS) Depressants Clinical Impact: Due to additive pharmacologic effect, the concomitant use of benzodiazepines or other CNS depressants, including alcohol, can increase the risk of hypotension respiratory depression, profound sedation, coma, and death [see Warnings and Precautions (5.3) ] . Intervention: Reserve concomitant prescribing of these drugs for use in patients for whom alternative treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor patients closely for signs of respiratory depression and sedation. Examples: Benzodiazepines and other sedatives/hypnotics, anxiolytics, tranquilizers, muscle relaxants, general anesthetics, antipsychotics, gabapentinoids (gabapentin or pregabalin), other opioids, alcohol. Serotonergic Drugs Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome [see Warnings and Precautions (5.8) ]. Intervention: If concomitant use is warranted, carefully observe the patient, particularly during treatment initiation and dose adjustment. Discontinue DEMEROL Injection if serotonin syndrome is suspected. Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue). Mixed Agonist/Antagonist and Partial Agonist Opioid Analgesics Clinical Impact: May reduce the analgesic effect of DEMEROL Injection and/or precipitate withdrawal symptoms. Intervention: Avoid concomitant use. Examples: Butorphanol, nalbuphine, pentazocine, buprenorphine. Muscle Relaxants Clinical Impact: Meperidine may enhance the neuromuscular blocking action of skeletal muscle relaxants and produce an increased degree of respiratory depression. Intervention: Monitor patients for signs of respiratory depression that may be greater than otherwise expected and decrease the dosage of DEMEROL Injection and/or the muscle relaxant as necessary. Examples: Cyclobenzaprine, metaxalone Diuretics Clinical Impact: Opioids can reduce the efficacy of diuretics by inducing the release of antidiuretic hormone. Intervention: Monitor patients for signs of diminished diuresis and/or effects on blood pressure and increase the dosage of the diuretic as needed. Anticholinergic Drugs Clinical Impact: The concomitant use of anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Intervention: Monitor patients for signs of urinary retention or reduced gastric motility when DEMEROL Injection is used concomitantly with anticholinergic drugs. Acyclovir Clinical Impact: The concomitant use of acyclovir may increase the plasma concentrations of meperidine and its metabolite, normeperidine. Intervention: If concomitant use of acyclovir and DEMEROL Injection is necessary, monitor patients for respiratory depression and sedation at frequent intervals. Cimetidine Clinical Impact: The concomitant use of cimetidine may reduce the clearance and volume of distribution of meperidine also the formation of the metabolite, normeperidine, in healthy subjects Intervention: If concomitant use cimetidine and DEMEROL Injection is necessary, monitor patients for respiratory depression and sedation at frequent intervals. Mixed Agonist/Antagonist and Partial Agonist Opioid Analgesics : Avoid use with DEMEROL Injection because they may reduce analgesic effect of DEMEROL Injection or precipitate withdrawal symptoms. ( 7 )

Store at 20°C to 25°C (68°F to 77°F), excursions permitted between 15°C to 30°C (59°F to 86°F). [See USP Controlled Room Temperature.]