EFAVIRENZ

Efavirenz is an HIV-1 specific, non-nucleoside, reverse transcriptase inhibitor (NNRTI). Efavirenz USP is chemically described as (S)-6-chloro-4-(cyclopropylethynyl)-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one. Its empirical formula is C 14 H 9 ClF 3 NO 2 and its structural formula is: Efavirenz USP is a white to slightly pink crystalline powder with a molecular mass of 315.68. It is practically insoluble in water (<10 microgram/mL). Tablets: Efavirenz are available as film-coated tablets for oral administration containing 600 mg of efavirenz USP and the following inactive ingredients: microcrystalline cellulose, sodium lauryl sulfate, croscarmellose sodium, hydroxypropyl cellulose, lactose monohydrate, magnesium stearate. The film coating contains Opadry® Yellow (hypromellose, titanium dioxide, iron oxide yellow and polyethylene glycol). Efavirenzstructure

INDICATIONS & USAGE Efavirenz tablets in combination with other antiretroviral agents is indicated for the treatment of human immunodeficiency virus type 1 (HIV-1) infection in adults and in pediatric patients at least 3 months old and weighing at least 3.5 kg. Efavirenz is a non-nucleoside reverse transcriptase inhibitor indicated in combination with other antiretroviral agents for the treatment of human immunodeficiency virus type 1 infection in adults and in pediatric patients at least 3 months old and weighing at least 3.5 kg. (1)

DOSAGE & ADMINISTRATION • Efavirenz tablets should be taken orally once daily on an empty stomach, preferably at bedtime. (2) • Recommended adult dose: 600 mg. (2.2) • Pediatric dosing is based on weight. (2.3) 2.1 Hepatic Function Monitor hepatic function prior to and during treatment with efavirenz tablets [see Warnings and Precautions ( 5.9)]. Efavirenz tablets are not recommended in patients with moderate or severe hepatic impairment (Child Pugh B or C) [see Warnings and Precautions (5.9) and Use in Specific Populationns ( 8.6)]. 2.2 Adults The recommended dosage of efavirenz tablets are 600 mg orally, once daily, in combination with a protease inhibitor and/or nucleoside analogue reverse transcriptase inhibitors (NRTIs). It is recommended that efavirenz tablets be taken on an empty stomach, preferably at bedtime. The increased efavirenz concentrations observed following administration of efavirenz tablets with food may lead to an increase in frequency of adverse reactions [see Clinical Pharmacology (12.3)]. Dosing at bedtime may improve the tolerability of nervous system symptoms [see Warnings and Precautions (5.6), Adverse Reactions (6.1), and Patient Counseling Information ( 17)]. Efavirenz tablets should be swallowed intact with liquid. Concomitant Antiretroviral Therapy Efavirenz tablets must be given in combination with other antiretroviral medications [see Indications and Usage (1), Warnings and Precautions (5.3), Drug Interactions (7.1), and Clinical Pharmacology (12.3)]. 2.3 Pediatric Patients It is recommended that efavirenz tablets be taken on an empty stomach, preferably at bedtime. Table 1 describes the recommended dose of efavirenz tablets for pediatric patients 3 months of age or older and weighing between 3.5 kg and 40 kg [see Clinical Pharmacology (12.3)]. The recommended dosage of efavirenz tablets for pediatric patients weighing 40 kg or greater is 600 mg once daily. Table 1: Efavirenz Tablets Dosing in Pediatric Patients Patient Body Weight Efavirenz Tablets Daily Dose Number of Tablets b and Strength to Administer at least 40 kg 600 mg one 600 mg tablet b Tablets must not be crushed.

• Efavirenz tablets are contraindicated in patients with previously demonstrated clinically significant hypersensitivity (eg, Stevens-Johnson syndrome, erythema multiforme, or toxic skin eruptions) to any of the components of this product. • Coadministration of efavirenz with elbasvir and grazoprevir is contraindicated [see Warnings and Precautions (5.1) and Drug Interactions ( 7.1)]. • Patients with previously demonstrated hypersensitivity (eg, Stevens-Johnson syndrome, erythema multiforme, or toxic skin eruptions) to any of the components of this product. (4) • Coadministration of efavirenz with elbasvir/grazoprevir.

The most significant adverse reactions observed in patients treated with efavirenz tablets are: • psychiatric symptoms [see Warnings and Precautions ( 5.5)], • nervous system symptoms [see Warnings and Precautions (5.6)], • rash [see Warnings and Precautions (5.8)]. • hepatotoxicity [see Warnings and Precautions ( 5.9)] Most common adverse reactions (>5%, moderate-severe) are impaired concentration, abnormal dreams, rash, dizziness, nausea, headache, fatigue, insomnia, and vomiting. (6) To report SUSPECTED ADVERSE REACTIONS, contact Hetero Labs Limited at 866-495-1995 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical studies are conducted under widely varying conditions, the adverse reaction rates reported cannot be directly compared to rates in other clinical studies and may not reflect the rates observed in clinical practice. Adverse Reactions in Adults The most common (>5% in either efavirenz treatment group) adverse reactions of at least moderate severity among patients in Study 006 treated with efavirenz tablets in combination with zidovudine/lamivudine or indinavir were rash, dizziness, nausea, headache, fatigue, insomnia, and vomiting. Selected clinical adverse reactions of moderate or severe intensity observed in ≥2% of efavirenz tablets-treated patients in two controlled clinical trials are presented in Table 2. Table 2: Selected Treatment-Emergent a Adverse Reactions of Moderate or Severe Intensity Reported in ≥2% of Efavirenz-Treated Patients in Studies 006 and ACTG 364 Adverse Reactions Study 006 LAM-, NNRTI-, and Protease Inhibitor-Naive Patients Study ACTG 364 NRTI-experienced, NNRTI-, and Protease Inhibitor-Naive Patients Efavirenz tablets b + ZDV/LAM (n=412) 180 weeks c Efavirenz tablets b + Indinavir (n=415) 102 weeks c Indinavir + ZDV/LAM (n=401) 76 weeks c Efavirenz tablets b + Nelfinavir + NRTIs (n=64) 71.1 weeks c Efavirenz tablets b + NRTIs (n=65) 70.9 weeks c Nelfinavir + NRTIs (n=66) 62.7 weeks c Body as a Whole Fatigue 8% 5% 9% 0 2% 3% Pain 1% 2% 8% 13% 6% 17% Central and Peripheral Nervous System Dizziness 9% 9% 2% 2% 6% 6% Headache 8% 5% 3% 5% 2% 3% Insomnia 7% 7% 2% 0 0 2% Concentration impaired 5% 3% <1% 0 0 0 Abnormal dreams 3% 1% 0 — — — Somnolence 2% 2% <1% 0 0 0 Anorexia 1% <1% <1% 0 2% 2% Gastrointestinal Nausea 10% 6% 24% 3% 2% 2% Vomiting 6% 3% 14% — — — Diarrhea 3% 5% 6% 14% 3% 9% Dyspepsia 4% 4% 6% 0 0 2% Abdominal pain 2% 2% 5% 3% 3% 3% Psychiatric Anxiety 2% 4% <1% — — — Depression 5% 4% <1% 3% 0 5% Nervousness 2% 2% 0 2% 0 2% Skin & Appendages Rash d 11% 16% 5% 9% 5% 9% Pruritus <1% 1% 1% 9% 5% 9% a Includes adverse events at least possibly related to study drug or of unknown relationship for Study 006. Includes all adverse events regardless of relationship to study drug for Study ACTG 364. b Efavirenz tablets provided as 600 mg once daily. c Median duration of treatment. d Includes erythema multiforme, rash, rash erythematous, rash follicular, rash maculopapular, rash petechial, rash pustular, and urticaria for Study 006 and macules, papules, rash, erythema, redness, inflammation, allergic rash, urticaria, welts, hives, itchy, and pruritus for ACTG 364. — = Not Specified. ZDV = zidovudine, LAM=lamivudine. Pancreatitis has been reported, although a causal relationship with efavirenz has not been established. Asymptomatic increases in serum amylase levels were observed in a significantly higher number of patients treated with efavirenz 600 mg than in control patients (see Laboratory Abnormalities ). Nervous System Symptoms For 1,008 patients treated with regimens containing efavirenz tablets and 635 patients treated with a control regimen in controlled trials, Table 3 lists the frequency of symptoms of different degrees of severity and gives the discontinuation rates for one or more of the following nervous system symptoms: dizziness, insomnia, impaired concentration, somnolence, abnormal dreaming, euphoria, confusion, agitation, amnesia, hallucinations, stupor, abnormal thinking, and depersonalization [see Warnings and Precautions (5.6)]. The frequencies of specific central and peripheral nervous system symptoms are provided in Table 2. Table 3: Percent of Patients with One or More Selected Nervous System Symptoms a,b Percent of Patients with: Efavirenz Tablets 600 mg Once Daily (n=1,008) % Control Groups (n=635) % Symptoms of any severity 52.7 24.6 Mild symptoms c 33.3 15.6 Moderate symptoms d 17.4 7.7 Severe symptoms e 2 1.3 Treatment discontinuation as a result of symptoms 2.1 1.1 a Includes events reported regardless of causality. b Data from Study 006 and three Phase 2/3 studies. c “Mild” = Symptoms which do not interfere with patient’s daily activities. d “Moderate” = Symptoms which may interfere with daily activities. e “Severe” = Events which interrupt patient’s usual daily activities. Psychiatric Symptoms Serious psychiatric adverse experiences have been reported in patients treated with efavirenz tablets. In controlled trials, psychiatric symptoms observed at a frequency greater than 2% among patients treated with efavirenz tablets or control regimens, respectively, were depression (19%, 16%), anxiety (13%, 9%), and nervousness (7%, 2%). Rash In controlled clinical trials, the frequency of rash (all grades, regardless of causality) was 26% for 1,008 adults treated with regimens containing efavirenz tablets and 17% for 635 adults treated with a control regimen. Most reports of rash were mild or moderate in severity. The frequency of Grade 3 rash was 0.8% for efavirenz tablets-treated patients and 0.3% for control groups, and the frequency of Grade 4 rash was 0.1% for efavirenz tablets and 0 for control groups. The discontinuation rates as a result of rash were 1.7% for efavirenz tablets-treated patients and 0.3% for control groups [see Warnings and Precautions (5.8)]. Experience with efavirenz tablets in patients who discontinued other antiretroviral agents of the NNRTI class is limited. Nineteen patients who discontinued nevirapine because of rash have been treated with efavirenz tablets. Nine of these patients developed mild-to-moderate rash while receiving therapy with efavirenz tablets, and two of these patients discontinued because of rash. Laboratory Abnormalities Selected Grade 3 to 4 laboratory abnormalities reported in ≥2% of efavirenz tablets-treated patients in two clinical trials are presented in Table 4. Table 4: Selected Grade 3 to 4 Laboratory Abnormalities Reported in ≥2% of Efavirenz-Treated Patients in Studies 006 and ACTG 364 Study 006 LAM-, NNRTI-, and Protease Inhibitor-Naive Patients Study ACTG 364 NRTI-experienced, NNRTI-, and Protease Inhibitor-Naive Patients Variable Limit Efavirenz tablets a +ZDV/LAM(n=412) 180 weeks b Efavirenz tablets a +Indinavir (n=415) 102 weeks b Indinavir +ZDV/LAM (n=401) 76 weeks b Efavirenz tablets a +Nelfinavir + NRTIs (n=64) 71.1 weeks b Efavirenz tablets a + NRTIs (n=65) 70.9 weeks b Nelfinavir + NRTIs (n=66) 62.7 weeks b Chemistry ALT >5 x ULN 5% 8% 5% 2% 6% 3% AST >5 x ULN 5% 6% 5% 6% 8% 8% GGT c >5 x ULN 8% 7% 3% 5% 0 5% Amylase >2 x ULN 4% 4% 1% 0 6% 2% Glucose >250 mg/dL 3% 3% 3% 5% 2% 3% Triglycerides d ³751mg/dL 9% 6% 6% 11% 8% 17% Hematology Neutrophils <750/mm 3 10% 3% 5% 2% 3% 2% a Efavirenz tablets provided as 600 mg once daily. b Median duration of treatment. c Isolated elevations of GGT in patients receiving efavirenz tablets may reflect enzyme induction not associated with liver toxicity. d Nonfasting. ZDV = zidovudine, LAM = lamivudine, ULN = upper limit of normal, ALT = alanine aminotransferase, AST = aspartate aminotransferase, GGT = gamma-glutamyltransferase. Patients Coinfected with Hepatitis B or C Liver function tests should be monitored in patients with a history of hepatitis B and/or C. In the long-term data set from Study 006, 137 patients treated with efavirenz tablets-containing regimens (median duration of therapy, 68 weeks) and 84 treated with a control regimen (median duration, 56 weeks) were seropositive at screening for hepatitis B (surface antigen positive) and/or C (hepatitis C antibody positive). Among these coinfected patients, elevations in AST to greater than five times ULN developed in 13% of patients in the efavirenz tablets arms and 7% of those in the control arm, and elevations in ALT to greater than five times ULN developed in 20% of patients in the efavirenz tablets arms and 7% of patients in the control arm. Among coinfected patients, 3% of those treated with efavirenz tablets-containing regimens and 2% in the control arm discontinued from the study because of liver or biliary system disorders [see Warnings and Precautions (5.9)]. Lipids Increases from baseline in total cholesterol of 10 to 20% have been observed in some uninfected volunteers receiving efavirenz. In patients treated with efavirenz tablets + zidovudine + lamivudine, increases from baseline in nonfasting total cholesterol and HDL of approximately 20% and 25%, respectively, were observed. In patients treated with efavirenz tablets + indinavir, increases from baseline in nonfasting cholesterol and HDL of approximately 40% and 35%, respectively, were observed. Nonfasting total cholesterol levels 240 mg/dL and 300 mg/dL were reported in 34% and 9%, respectively, of patients treated with efavirenz tablets + zidovudine + lamivudine; 54% and 20%, respectively, of patients treated with efavirenz tablets + indinavir; and 28% and 4%, respectively, of patients treated with indinavir + zidovudine + lamivudine. The effects of efavirenz tablets on triglycerides and LDL in this study were not well characterized since samples were taken from nonfasting patients. The clinical significance of these findings is unknown [see Warnings and Precautions (5.11)]. Adverse Reactions in Pediatric Patients Because clinical studies are conducted under widely varying conditions, the adverse reaction rates reported cannot be directly compared to rates in other clinical studies and may not reflect the rates observed in clinical practice. Assessment of adverse reactions is based on three clinical trials in 182 HIV-1 infected pediatric patients (3 months to 21 years of age) who received efavirenz tablets in combination with other antiretroviral agents for a median of 123 weeks. The adverse reactions observed in the three trials were similar to those observed in clinical trials in adults except that rash was more common in pediatric patients (32% for all grades regardless of causality) and more often of higher grade (ie, more severe). Two (1.1%) pediatric patients experienced Grade 3 rash (confluent rash with fever, generalized rash), and four (2.2%) pediatric patients had Grade 4 rash (all erythema multiforme). Five pediatric patients (2.7%) discontinued from the study because of rash [see Warnings and Precautions (5.8)]. 6.2 Postmarketing Experience The following adverse reactions have been identified during postapproval use of efavirenz tablets. Because these reactions are reported voluntarily from a population of unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Body as a Whole: allergic reactions, asthenia, redistribution/accumulation of body fat [see Warnings and Precautions (5.13)] Central and Peripheral Nervous System: abnormal coordination, ataxia, cerebellar coordination and balance disturbances, convulsions, hypoesthesia, paresthesia, neuropathy, tremor, vertigo Endocrine: gynecomastia Gastrointestinal: constipation, malabsorption Cardiovascular: flushing, palpitations Liver and Biliary System: hepatic enzyme increase, hepatic failure, hepatitis. Metabolic and Nutritional: hypercholesterolemia, hypertriglyceridemia. Musculoskeletal: arthralgia, myalgia, myopathy Psychiatric: aggressive reactions, agitation, delusions, emotional lability, mania, neurosis, paranoia, psychosis, suicide, catatonia Respiratory: dyspnea Skin and Appendages: erythema multiforme, photoallergic dermatitis, Stevens-Johnson syndrome Special Senses: abnormal vision, tinnitus

• Coadministration of efavirenz can alter the concentrations of other drugs and other drugs may alter the concentrations of efavirenz. The potential for drug-drug interactions should be considered before and during therapy. (7) 7.1 Potential for Efavirenz to Affect other Drugs Efavirenz has been shown in vivo to induce CYP3A and CYP2B6. Other compounds that are substrates of CYP3A or CYP2B6 may have decreased plasma concentrations when coadministered with efavirenz tablets. 7.2 Potential for Other Drugs to Affect Efavirenz Drugs that induce CYP3A activity (eg, phenobarbital, rifampin, rifabutin) would be expected to increase the clearance of efavirenz resulting in lowered plasma concentrations [see Dosage and Administration (2.2)]. 7.3 QT Prolonging Drugs There is limited information available on the potential for a pharmacodynamic interaction between efavirenz and drugs that prolong the QTc interval. QTc prolongation has been observed with the use of efavirenz [see Clinical Pharmacology ( 12.2)]. Consider alternatives to efavirenz when coadministered with a drug with a known risk of Torsade de Pointes. 7.4 Established and Other Potentially Significant Drug Interactions Drug interactions with efavirenz tablets are summarized in Tables 5. For pharmacokinetics data, [see Clinical Pharmacology (12.3)] Tables 7 and 8. This table includes potentially significant interactions, but is not all inclusive. Table 5: Established and Other Potentially Significant Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies or Predicted Interaction Concomitant Drug Class: Drug Name Effect Clinical Comment HIV antiviral agents Protease inhibitor: Fosamprenavir calcium ↓amprenavir Fosamprenavir (unboosted): Appropriate doses of the combinations with respect to safety and efficacy have not been established. Fosamprenavir/ritonavir: An additional 100 mg/day (300 mg total) of ritonavir is recommended when efavirenz tablets are administered with fosamprenavir/ritonavir once daily. No change in the ritonavir dose is required when efavirenz tablets are administered with fosamprenavir plus ritonavir twice daily. Protease inhibitor: Atazanavir ↓atazanavir * Treatment-naive patients: When coadministered with efavirenz tablets, the recommended dose of atazanavir is 400 mg with ritonavir 100 mg (together once daily with food) and efavirenz tablets 600 mg (once daily on an empty stomach, preferably at bedtime). Treatment-experienced patients: Coadministration of efavirenz tablets and atazanavir is not recommended. Protease inhibitor: Indinavir ↓indinavir * The optimal dose of indinavir, when given in combination with efavirenz tablets, is not known. Increasing the indinavir dose to 1,000 mg every 8 hours does not compensate for the increased indinavir metabolism due to efavirenz tablets. Protease inhibitor: Lopinavir/ritonavir ↓lopinavir * Lopinavir/ritonavir once daily dosing is not recommended when coadministered with efavirenz tablets. The dose of lopinavir/ritonavir must be increased when coadministered with efavirenz tablets. See the lopinavir/ritonavir prescribing information for dose adjustments of lopinavir/ritonavir when coadministered with efavirenz in adult and pediatric patients. Protease inhibitor: Ritonavir ↑ritonavir * ­ ↑efavirenz * Monitor for elevation of liver enzymes and for adverse clinical experiences (e.g., dizziness, nausea, paresthesia) when efavirenz tablet is coadministered with ritonavir. Protease inhibitor: Saquinavir ↓saquinavir * Appropriate doses of the combination of efavirenz tablets and saquinavir/ritonavir with respect to safety and efficacy have not been established. NNRTI: Other NNRTIs ­ ↑ or ↓efavirenz and/or NNRTI Combining two NNRTIs has not been shown to be beneficial. ↑Efavirenz tablets should not be coadministered with other NNRTIs. CCR5 co-receptor antagonist: Maraviroc ↓maraviroc * Refer to the full prescribing information for maraviroc for guidance on coadministration with efavirenz. Hepatitis C antiviral agents Boceprevir ↓ boceprevir * Concomitant administration of boceprevir with efavirenz tablet is not recommended because it may result in loss of therapeutic effect of boceprevir. Elbasvir/Grazoprevir ↓ elbasvir ↓ grazoprevir Coadministration of clopidogrel with elbasvir/grazoprevir is contraindicated [ see Contraindications (4) ] because it may lead to loss of virologic response to elbasvir/grazoprevir. Pibrentasvir/Glecaprevir ↓ pibrentasvir ↓ glecaprevir Coadministration of clopidogrel is not recommended because it may lead to reduced therapeutic effect of pibrentasvir/glecaprevir. Simeprevir ↓ simeprevir * ↔efavirenz * Concomitant administration of simprevir with efavirenz tablet is not recommended because it may result in loss of therapeutic effect of simeprevir. Velpatasvir/ Sofosbuvir ↓ velpatasvir Coadministration of efavirenz and sofosbuvir/velpatasvir is not recommended because it may result in loss of therapeutic effect of sofosbuvir/velpatasvir. Velpatasvir /Sofosbuvir /Voxilaprevir velpatasvir sofosbuvir Coadministration of efavirenz and sofosbuvir/velpatasvir/voxilaprevir is not recommended because it may result in loss of therapeutic effect of sofosbuvir/velpatasvir/voxilaprevir. Other agents Anticoagulant: Warfarin ­ ↑ or ↓warfarin Monitor INR and adjust warfarin dosage if necessary. Anticonvulsants: Carbamazepine ↓carbamazepine * ↓efavirenz * There are insufficient data to make a dose recommendation for efavirenz. Alternative anticonvulsant treatment should be used. Phenytoin Phenobarbital ↓anticonvulsant ↓efavirenz Potential for reduction in anticonvulsant and/or efavirenz plasma levels; periodic monitoring of anticonvulsant plasma levels should be conducted. Antidepressants: Bupropion Sertraline ↓bupropion * ↓sertraline * Increases in bupropion dosage should be guided by clinical response. Bupropion dose should not exceed the maximum recommended dose. Increases in sertraline dosage should be guided by clinical response. Antifungals: Voriconazole ↓voriconazole * ­ ↑efavirenz * Efavirenz tablets and voriconazole should not be coadministered at standard doses. When voriconazole is coadministered with efavirenz tablets, voriconazole maintenance dose should be increased to 400 mg every 12 hours and efavirenz tablets dose should be decreased to 300 mg once daily using the capsule formulation. Efavirenz tablets must not be broken. [ See Dosage and Administration (2.2) and Clinical Pharmacology (12.3, Tables 7 and 8) .] Itraconazole ↓itraconazole * ↓hydroxyitraconazole * Consider alternative antifungal treatment because no dose recommendation for itraconazole can be made. Ketoconazole ↓ketoconazole Consider alternative antifungal treatment because no dose recommendation for ketoconazole can be made. Posaconazole ↓posaconazole * Avoid concomitant use unless the benefit outweighs the risks. Anti-infective: Clarithromycin ↓ clarithromycin * ­ ↑14-OH metabolite * Consider alternatives to macrolide antibiotics because of the risk of QT interval prolongation. Antimycobacterials: Rifabutin ↓ rifabutin * Increase daily dose of rifabutin by 50%. Consider doubling the rifabutin dose in regimens where rifabutin is given 2 or 3 times a week. Rifampin ↓efavirenz * Increase efavirenz tablets to 800 mg once daily when coadministered with rifampin to patients weighing 50 kg or more. Antimalarials: Artemether/ lumefantrine Atovaquone/ proguanil ↓ artemether* ↓ dihydroartemisinin* ↓ lumefantrine* ↓ atovaquone ↓ proguanil Consider alternatives to artemether/lumefantrine because of the risk of QT interval prolongation. Concomitant administration is not recommended. Calcium channel blockers: Diltiazem ↓diltiazem * ↓desacetyl diltiazem * ↓N-monodesmethyl diltiazem * Diltiazem dose adjustments should be guided by clinical response (refer to the full prescribing information for diltiazem). No dose adjustment of efavirenz is necessary when administered with diltiazem. Others (eg, felodipine, nicardipine, nifedipine, verapamil) ↓ calcium channel blocker When coadministered with efavirenz tablets, dosage adjustment of calcium channels blocker may be needed and should be guided by clinical response (refer to the full prescribing information for the calcium channel blocker). HMG-CoA reductase inhibitors: Atorvastatin Pravastatin Simvastatin ↓atorvastatin * ↓pravastatin * ↓simvastatin * Plasma concentrations of atorvastatin, pravastatin, and simvastatin decreased. Consult the full prescribing information for the HMG-CoA reductase inhibitor for guidance on individualizing the dose. Hormonal contraceptives: Oral Ethinyl estradiol/Norgestimate Implant Etonogestrel ↓ active metabolites of norgestimate * ↓ etonogestrel A reliable method of barrier contraception should be used in addition to hormonal contraceptives. A reliable method of barrier contraception should be used in addition to hormonal contraceptives. Decreased exposure of etonogestrel may be expected. There have been postmarketing reports of contraceptive failure with etonogestrel in efavirenz-exposed patients. Immunosuppressants: Cyclosporine, tacrolimus, sirolimus, and others metabolized by CYP3A ↓ immunosuppressant Dose adjustments of the immunosuppressant may be required. Close monitoring of immunosuppressant concentrations for at least 2 weeks (until stable concentrations are reached) is recommended when starting or stopping treatment with efavirenz. Narcotic analgesic: Methadone ↓methadone * Monitor for signs of methadone withdrawal and increase methadone dose if required to alleviate withdrawal symptoms. * The interaction between efavirenz tablets and the drug was evaluated in a clinical study. All other drug interactions shown are predicted.This table is not all-inclusive. 7.5 Drugs Without Clinically Significant Interactions with Efavirenz No dosage adjustment is recommended when efavirenz is given with the following: aluminum/magnesium hydroxide antacids, azithromycin, cetirizine, famotidine, fluconazole, lorazepam, nelfinavir, nucleoside reverse transcriptase inhibitors (abacavir, emtricitabine, lamivudine, stavudine, tenofovir disoproxil fumarate, zidovudine), paroxetine, and raltegravir. 7.6 Cannabinoid Test Interaction Efavirenz does not bind to cannabinoid receptors. False-positive urine cannabinoid test results have been reported with some screening assays in uninfected and HIV-infected subjects receiving efavirenz. Confirmation of positive screening tests for cannabinoids by a more specific method is recommended.