Drug Interaction Report

CONTRAINDICATED: Naltrexone can antagonize the effects of opioids via competitive inhibition of opioid receptors. Patients receiving naltrexone may not benefit from opioid-containing medications such as cough and cold products, antidiarrheal preparations, and narcotic analgesics. Likewise, patients dependent on opioids may experience withdrawal symptoms when given naltrexone. Following use of naltrexone, patients may have increased sensitivity to opioids.

**Note: This warning does not apply to opioid products that are specifically formulated with naltrexone to deter abuse via snorting or intravenous injection when crushed.**

MANAGEMENT: The use of naltrexone is considered contraindicated in patients receiving opioids or dependent on opioids, including those maintained on opiate agonists (e.g., methadone) or partial agonists (e.g., buprenorphine). Naltrexone should also not be given to patients in acute opioid withdrawal. In an urgent situation when analgesia may be required in a patient who has received full blocking doses of naltrexone, consideration should be given to regional analgesia, conscious sedation with a benzodiazepine, use of non-opioid analgesics, or general anesthesia. If opioid analgesia is required, the amount of opioid needed may be greater than usual, and the resulting respiratory depression may be deeper and more prolonged. A rapidly-acting opioid analgesic that minimizes the duration of respiratory depression is preferred. Clinicians should be aware that reversal of full naltrexone blockade by administration of large doses of opiates can cause histamine release. Therefore, patients may experience non-opioid receptor-mediated effects such as facial swelling, itching, generalized erythema, and bronchoconstriction. Irrespective of the drug chosen to reverse naltrexone blockade, the patient should be monitored closely by appropriately trained personnel in a setting equipped and staffed for cardiopulmonary resuscitation.

GENERALLY AVOID: Coadministration of naltrexone with other agents known to induce hepatotoxicity may potentiate the risk of liver injury. Naltrexone, especially in larger than recommended doses (more than 50 mg/day), has been associated with hepatocellular injury, hepatitis, and elevations in liver transaminases and bilirubin. Other potential causative or contributory etiologies identified include preexisting alcoholic liver disease, hepatitis B and/or C infection, and concomitant usage of other hepatotoxic drugs.

MANAGEMENT: The use of naltrexone with other potentially hepatotoxic agents should be avoided whenever possible (e.g., acetaminophen; alcohol; androgens and anabolic steroids; antituberculous agents; azole antifungal agents; ACE inhibitors; cyclosporine (high dosages); disulfiram; endothelin receptor antagonists; interferons; ketolide and macrolide antibiotics; kinase inhibitors; minocycline; nonsteroidal anti-inflammatory agents; nucleoside reverse transcriptase inhibitors; proteasome inhibitors; retinoids; sulfonamides; tamoxifen; thiazolidinediones; tolvaptan; vincristine; zileuton; anticonvulsants such as carbamazepine, hydantoins, felbamate, and valproic acid; lipid-lowering medications such as fenofibrate, lomitapide, mipomersen, niacin, and statins; herbals and nutritional supplements such as black cohosh, chaparral, comfrey, DHEA, kava, pennyroyal oil, and red yeast rice). Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, right upper quadrant pain, dark urine, pale stools, and jaundice. Periodic monitoring of hepatic function is advisable.

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics including oxycodone. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of oxycodone. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism of oxycodone by certain compounds present in grapefruit, resulting in decreased formation of metabolites noroxycodone and noroxymorphone and increased formation of oxymorphone due to a presumed shifting of oxycodone metabolism towards the CYP450 2D6-mediated route. In 12 healthy, nonsmoking volunteers, administration of a single 10 mg oral dose of oxycodone hydrochloride on day 4 of a grapefruit juice treatment phase (200 mL three times a day for 5 days) increased mean oxycodone peak plasma concentration (Cmax), systemic exposure (AUC) and half-life by 48%, 67% and 17% (from 3.5 to 4.1 hours), respectively, compared to administration during an equivalent water treatment phase. Grapefruit juice also decreased the metabolite-to-parent AUC ratio of noroxycodone by 44% and that of noroxymorphone by 45%. In addition, oxymorphone Cmax and AUC increased by 32% and 56%, but the metabolite-to-parent AUC ratio remained unchanged. Pharmacodynamic changes were modest and only self-reported performance was significantly impaired after grapefruit juice. Analgesic effects were not affected.

MANAGEMENT: Patients should not consume alcoholic beverages or use drug products that contain alcohol during treatment with oxycodone. Any history of alcohol or illicit drug use should be considered when prescribing oxycodone, and therapy initiated at a lower dosage if necessary. Patients should be closely monitored for signs and symptoms of sedation, respiratory depression, and hypotension. Due to a high degree of interpatient variability with respect to grapefruit juice interactions, patients treated with oxycodone may also want to avoid or limit the consumption of grapefruit and grapefruit juice.

MONITOR: Concomitant use of asparaginase with other hepatotoxic agents may potentiate the risk of liver injury. Asparaginase-associated hepatotoxicity has been reported more commonly in adults than in children and has been strongly associated with obesity. Hepatomegaly, acute severe hepatotoxicity, and fatal liver failure have been reported with asparaginase treatment in adults. Also, asparaginase may increase the toxicity of drugs bound to plasma proteins or metabolized by the liver.

MANAGEMENT: The risk of additive hepatotoxicity should be considered when asparaginase is used with other hepatotoxic agents (e.g., alcohol, androgens, antituberculosis agents, azole antifungal agents, ACE inhibitors, macrolide antibiotics, nonsteroidal anti-inflammatory agents, nucleoside reverse transcriptase inhibitors, sulfonamides, thiazolidinediones, and statins). Liver function tests should be monitored at regular intervals during asparaginase treatment with or without other hepatotoxic drugs. Patients should be advised to seek medical attention if they experience potential symptoms of hepatotoxicity such as right upper quadrant pain, increasing abdominal size, fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, dark urine, pale stools, and jaundice.

GENERALLY AVOID: Coadministration of naltrexone with other agents known to induce hepatotoxicity may potentiate the risk of liver injury. Naltrexone, especially in larger than recommended doses (more than 50 mg/day), has been associated with hepatocellular injury, hepatitis, and elevations in liver transaminases and bilirubin. Other potential causative or contributory etiologies identified include preexisting alcoholic liver disease, hepatitis B and/or C infection, and concomitant usage of other hepatotoxic drugs.

MANAGEMENT: The use of naltrexone with other potentially hepatotoxic agents should be avoided whenever possible (e.g., acetaminophen; alcohol; androgens and anabolic steroids; antituberculous agents; azole antifungal agents; ACE inhibitors; cyclosporine (high dosages); disulfiram; endothelin receptor antagonists; interferons; ketolide and macrolide antibiotics; kinase inhibitors; minocycline; nonsteroidal anti-inflammatory agents; nucleoside reverse transcriptase inhibitors; proteasome inhibitors; retinoids; sulfonamides; tamoxifen; thiazolidinediones; tolvaptan; vincristine; zileuton; anticonvulsants such as carbamazepine, hydantoins, felbamate, and valproic acid; lipid-lowering medications such as fenofibrate, lomitapide, mipomersen, niacin, and statins; herbals and nutritional supplements such as black cohosh, chaparral, comfrey, DHEA, kava, pennyroyal oil, and red yeast rice). Patients should be advised to seek medical attention if they experience potential signs and symptoms of hepatotoxicity such as fever, rash, itching, anorexia, nausea, vomiting, fatigue, malaise, right upper quadrant pain, dark urine, pale stools, and jaundice. Periodic monitoring of hepatic function is advisable.