TENOFOVIR DISOPROXIL Drug Interactions: What You Need to Know

INTERACTIONS This section describes clinically relevant drug interactions with tenofovir disoproxil fumarate tablets. Drug interactions trials are described elsewhere in the labeling [See Clinical Pharmacology ( 12.3 )].

• Tenofovir disoproxil fumarate increases didanosine concentrations. Dose reduction and close monitoring for didanosine toxicity are warranted. (7.2)
• Coadministration decreases atazanavir concentrations. When coadministered with tenofovir disoproxil fumarate, use atazanavir given with ritonavir. (7.2)
• Coadministration of tenofovir disoproxil fumarate with certain HIV-1 protease inhibitors or certain drugs to treat HCV increases tenofovir concentrations. Monitor for evidence of tenofovir toxicity. (7.2)
• Consult Full Prescribing Information prior to and during treatment for important drug interactions. (7.2)

7.1 Drugs Affecting Renal Function Tenofovir is primarily eliminated by the kidneys <span class="opacity-50 text-xs">[see Clinical Pharmacology ( 12.3)]</span>. Coadministration of tenofovir disoproxil fumarate tablets with drugs that are eliminated by active tubular secretion may increase concentrations of tenofovir and/or the coadministered drug. Some examples include, but are not limited to, acyclovir, cidofovir, ganciclovir, valacyclovir, valganciclovir, aminoglycosides (e.g., gentamicin), and high-dose or multiple NSAIDs <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.2)]</span>. Drugs that decrease renal function may increase concentrations of tenofovir. In the treatment of chronic hepatitis B, tenofovir disoproxil fumarate tablets should not be administered in combination with HEPSERA (adefovir dipivoxil).

7.2 Established and Significant Interactions Table 11 provides a listing of established or clinically significant drug interactions. The drug interactions described are based on studies conducted with tenofovir DF <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.3)]</span>.

Table

11 Established and Significanta Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Trials Concomitant Drug Class: Drug Name Effect on Concentration b Clinical Comment NRTI: didanosine ↑ didanosine Patients receiving tenofovir disoproxil fumarate tablets and didanosine should be monitored closely for didanosine-associated adverse reactions. Discontinue didanosine in patients who develop didanosine-associated adverse reactions. Higher didanosine concentrations could potentiate didanosine-associated adverse reactions, including pancreatitis, and neuropathy. Suppression of CD4+ cell counts has been observed in patients receiving tenofovir disoproxil fumarate tablets with didanosine 400 mg daily. In patients weighing greater than 60 kg, reduce the didanosine dose to 250 mg when it is coadministered with tenofovir disoproxil fumarate tablets. In patients weighing less than 60 kg, reduce the didanosine dose to 200 mg when it is coadministered with tenofovir disoproxil fumarate tablets. When coadministered, tenofovir disoproxil fumarate tablets and Videx EC may be taken under fasted conditions or with a light meal (less than 400 kcal, 20% fat). HIV-1 Protease Inhibitors : atazanavir lopinavir/ritonavir atazanavir/ritonavir darunavir/ritonavir ↓ atazanavir ↑ tenofovir When coadministered with tenofovir disoproxil fumarate tablets, atazanavir 300 mg should be given with ritonavir 100 mg. Monitor patients receiving tenofovir disoproxil fumarate tablets concomitantly with lopinavir/ritonavir, ritonavir-boosted atazanavir, or ritonavir-boosted darunavir for tenofovir DF-associated adverse reactions. Discontinue tenofovir disoproxil fumarate tablets in patients who develop tenofovir DF-associated adverse reactions. Hepatitis C Antiviral Agents: sofosbuvir/velpatasvir sofosbuvir/velpatasvir/ voxilaprevir ledipasvir/sofosbuvir ↑ tenofovir Monitor patients receiving tenofovir disoproxil fumarate tablets concomitantly with EPCLUSA ® (sofosbuvir/velpatasvir) or VOSEVI ® (sofosbuvir/velpatasvir/voxilaprevir) for adverse reactions associated with tenofovir DF. Monitor patients receiving tenofovir disoproxil fumarate tablets concomitantly with HARVONI ® (ledipasvir/sofosbuvir) without an HIV-1 protease inhibitor/ritonavir or an HIV-1 protease inhibitor/cobicistat combination for adverse reactions associated with tenofovir DF. In patients receiving tenofovir disoproxil fumarate tablets concomitantly with HARVONI and an HIV-1 protease inhibitor/ritonavir or an HIV-1 protease inhibitor/cobicistat combination, consider an alternative HCV or antiretroviral therapy, as the safety of increased tenofovir concentrations in this setting has not been established. If coadministration is necessary, monitor for adverse reactions associated with tenofovir DF. a. This table is not all inclusive. b. ↑=Increase, ↓=Decrease

None. None. ( 4 )

AND PRECAUTIONS

• New onset or worsening renal impairment: Can include acute renal failure and Fanconi syndrome. Assess estimated creatinine clearance before initiating treatment with tenofovir disoproxil fumarate tablets. In patients at risk for renal dysfunction, assess estimated creatinine clearance, serum phosphorus, urine glucose, and urine protein before initiating treatment with tenofovir disoproxil fumarate tablets and periodically during treatment. Avoid administering tenofovir disoproxil fumarate tablets with concurrentor recent use of nephrotoxic drugs. (5.2)
• Lactic acidosis/severe hepatomegaly with steatosis: Discontinue treatment in patients who develop symptoms or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity. (5.3)
• Coadministration with other products: Do not use with other tenofovir-containing products (e.g., ATRIPLA, BIKTARVY, COMPLERA, DESCOVY, GENVOYA, ODEFSEY, STRIBILD, TRUVADA, or VEMLIDY). Do not administer in combination with HEPSERA. (5.4)
• HIV testing: HIV antibody testing should be offered to all HBV-infected patients before initiating therapy with tenofovir disoproxil fumarate tablets. Tenofovir disoproxil fumarate tablets should only be used as part of an appropriate antiretroviral combination regimen in HIV-infected patients with or without HBV coinfection. (5.5)
• Decreases in bone mineral density (BMD): Consider assessment of BMD in patients with a history of pathologic fracture or other risk factors for osteoporosis or bone loss. (5.6)
• Immune reconstitution syndrome: Observed in HIV-infected patients. May necessitate further evaluation and treatment. (5.7)
• Triple nucleoside-only regimens: Early virologic failure has been reported in HIV-infected patients. Monitor carefully and consider treatment modification. (5.8)

5.1 Exacerbation of Hepatitis after Discontinuation of Treatment Discontinuation of anti-HBV therapy, including tenofovir disoproxil fumarate tablets, may be associated with severe acute exacerbations of hepatitis. Patients infected with HBV who discontinue tenofovir disoproxil fumarate tablets should be closely monitored with both clinical and laboratory follow-up for at least several months after stopping treatment. If appropriate, resumption of anti-hepatitis B therapy may be warranted.

5.2 New Onset or Worsening Renal Impairment Tenofovir is principally eliminated by the kidney. Renal impairment, including cases of acute renal failure and Fanconi syndrome (renal tubular injury with severe hypophosphatemia), has been reported with the use of tenofovir disoproxil fumarate tablets [See Adverse Reactions (6.2)]. It is recommended that estimated creatinine clearance be assessed in all patients prior to initiating therapy and as clinically appropriate during therapy with tenofovir disoproxil fumarate tablets. In patients at risk of renal dysfunction, including patients who have previously experienced renal events while receiving HEPSERA ®, it is recommended that estimated creatinine clearance, serum phosphorus, urine glucose, and urine protein be assessed prior to initiation of tenofovir disoproxil fumarate tablets, and periodically during tenofovir disoproxil fumarate tablets therapy. Dosing interval adjustment of tenofovir disoproxil fumarate tablets and close monitoring of renal function are recommended in all patients with creatinine clearance below 50 mL/min [See Dosage and Administration (2.3)]. No safety or efficacy data are available in patients with renal impairment who received tenofovir disoproxil fumarate tablets using these dosing guidelines, so the potential benefit of tenofovir disoproxil fumarate tablets therapy should be assessed against the potential risk of renal toxicity. Tenofovir disoproxil fumarate tablets should be avoided with concurrent or recent use of a nephrotoxic agent (e.g., high-dose or multiple non-steroidal anti-inflammatory drugs (NSAIDs)) [See Drug Interactions (7.1)]. Cases of acute renal failure after initiation of high dose or multiple NSAIDs have been reported in HIV-infected patients with risk factors for renal dysfunction who appeared stable on tenofovir DF. Some patients required hospitalization and renal replacement therapy. Alternatives to NSAIDs should be considered, if needed, in patients at risk for renal dysfunction. Persistent or worsening bone pain, pain in extremities, fractures and/or muscular pain or weakness may be manifestations of proximal renal tubulopathy and should prompt an evaluation of renal function in at-risk patients.

5.3 Lactic Acidosis/Severe Hepatomegaly with Steatosis Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs, including tenofovir DF, alone or in combination with other antiretrovirals. Treatment with tenofovir disoproxil fumarate tablets should be suspended in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (which may include hepatomegaly and steatosis even in the absence of marked transaminase elevations).

5.4 Coadministration with Other Products Tenofovir disoproxil fumarate tablets should not be used in combination with other drugs containing tenofovir DF or tenofovir alafenamide, including ATRIPLA, BIKTARVY, COMPLERA, DESCOVY, GENVOYA, ODEFSEY, STRIBILD, TRUVADA, or VEMLIDY. Tenofovir disoproxil fumarate tablets should not be administered in combination with HEPSERA (adefovir dipivoxil) [See Drug Interactions (7.2) ].

5.5 Patients Coinfected with HIV-1 and HBV Due to the risk of development of HIV-1 resistance, tenofovir disoproxil fumarate tablets should only be used in HIV-1 and HBV coinfected patients as part of an appropriate antiretroviral combination regimen. HIV-1 antibody testing should be offered to all HBV-infected patients before initiating therapy with tenofovir disoproxil fumarate tablets. It is also recommended that all patients with HIV-1 be tested for the presence of chronic hepatitis B before initiating treatment with tenofovir disoproxil fumarate tablets.

5.6 Bone Effects Bone Mineral Density: In clinical trials in HIV-1 infected adults, tenofovir disoproxil fumarate tablets were associated with slightly greater decreases in bone mineral density (BMD) and increases in biochemical markers of bone metabolism, suggesting increased bone turnover relative to comparators. Serum parathyroid hormone levels and 1,25 Vitamin D levels were also higher in subjects receiving tenofovir disoproxil fumarate tablets [See Adverse Reactions (6.1)]. Clinical trials evaluating tenofovir disoproxil fumarate tablets in pediatric and adolescent subjects were conducted. Under normal circumstances, BMD increases rapidly in pediatric patients. In HIV-1 infected subjects aged 2 years to less than 18 years, bone effects were similar to those observed in adult subjects and suggest increased bone turnover. Total body BMD gain was less in the tenofovir disoproxil fumarate-treated HIV-1 infected pediatric subjects as compared to the control groups. Similar trends were observed in chronic hepatitis B infected adolescent subjects aged 12 years to less than 18 years. In all pediatric trials, skeletal growth (height) appeared to be unaffected [See Adverse Reactions (6.1)]. The effects of tenofovir disoproxil fumarate-associated changes in BMD and biochemical markers on long-term bone health and future fracture risk are unknown. Assessment of BMD should be considered for adults and pediatric patients who have a history of pathologic bone fracture or other risk factors for osteoporosis or bone loss. Although the effect of supplementation with calcium and vitamin D was not studied, such supplementation may be beneficial for all patients. If bone abnormalities are suspected then appropriate consultation should be obtained.

Mineralization

Defects: Cases of osteomalacia associated with proximal renal tubulopathy, manifested as bone pain or pain in extremities and which may contribute to fractures, have been reported in association with the use of tenofovir disoproxil fumarate tablets [See Adverse Reactions (6.2)]. Arthralgias and muscle pain or weakness have also been reported in cases of proximal renal tubulopathy. Hypophosphatemia and osteomalacia secondary to proximal renal tubulopathy should be considered in patients at risk of renal dysfunction who present with persistent or worsening bone or muscle symptoms while receiving products containing tenofovir DF [See Warnings and Precautions (5.2)].

5.7 Immune Reconstitution Syndrome Immune reconstitution syndrome has been reported in HIV-infected patients treated with combination antiretroviral therapy, including tenofovir disoproxil fumarate tablets. During the initial phase of combination antiretroviral treatment, patients whose immune system responds may develop an inflammatory response to indolent or residual opportunistic infections (such as Mycobacterium avium infection, cytomegalovirus, Pneumocystis jirovecii pneumonia [PCP], or tuberculosis), which may necessitate further evaluation and treatment. Autoimmune disorders (such as Graves’ disease, polymyositis, and Guillain-Barré syndrome) have also been reported to occur in the setting of immune reconstitution; however, the time to onset is more variable, and can occur many months after initiation of treatment.

5.8 Early Virologic Failure Clinical trials in HIV-infected subjects have demonstrated that certain regimens that only contain three nucleoside reverse transcriptase inhibitors (NRTI) are generally less effective than triple drug regimens containing two NRTIs in combination with either a non-nucleoside reverse transcriptase inhibitor or a HIV-1 protease inhibitor. In particular, early virological failure and high rates of resistance substitutions have been reported. Triple nucleoside regimens should therefore be used with caution. Patients on a therapy utilizing a triple nucleoside-only regimen should be carefully monitored and considered for treatment modification.