Emtricitabine/tenofovir alafenamide Disease Interactions

Severe acute exacerbations of HBV have been reported in HIV-1/HBV-coinfected patients who have discontinued products containing emtricitabine, lamivudine, and/or tenofovir disoproxil fumarate (DF) and may occur with discontinuation of tenofovir alafenamide-containing products. It is recommended that all patients with HIV-1 infection be tested for the presence of HBV before or when initiating products containing emtricitabine, lamivudine, tenofovir DF, or tenofovir alafenamide. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in HIV-1/HBV-coinfected patients who discontinue products (including fixed-dose combination products) that contain emtricitabine, lamivudine, tenofovir DF, or tenofovir alafenamide. If appropriate, initiation or resumption of antihepatitis B therapy may be warranted, especially in patients with advanced liver disease or cirrhosis since posttreatment exacerbation of hepatitis may lead to hepatic decompensation and liver failure.

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Hepatotoxicity including lactic acidosis, severe hepatomegaly with steatosis, fulminant hepatitis, and hepatic failure has been associated with the use of some nucleoside reverse transcriptase inhibitors (NRTIs) alone or in combination with other antiretroviral agents. Therapy with NRTIs should be administered cautiously in patients with preexisting liver disease, a history of alcohol abuse, or hepatitis. Therapy should be suspended if clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity occur. The use of abacavir is contraindicated in patients with moderate to severe liver dysfunction as its safety and efficacy have not been established in these patients.

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Emtricitabine is removed by hemodialysis. When started within 1.5 hours of emtricitabine dosing, about 30% of the dose was removed over a 3-hour hemodialysis session (blood flow rate of 400 mL/min and a dialysate flow rate of 600 mL/min). If dosing on day of hemodialysis, emtricitabine should be administered after hemodialysis.

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Emtricitabine is primarily eliminated by the kidney. Dosage adjustment of emtricitabine is recommended for patients with CrCl below 50 mL/min or in patients with ESRD requiring dialysis, in accordance with the manufacturer product information. Clinical response to treatment and renal function should be closely monitored.

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In clinical trials, tenofovir disoproxil fumarate (DF) was associated with slightly greater reductions in bone mineral density (BMD) and increases in biochemical markers of bone metabolism, suggesting increased bone turnover relative to comparators. The effects of tenofovir DF-associated changes in BMD and biochemical markers on long-term bone health and future fracture risk have not been established. Calcium and vitamin D supplementation may be beneficial; however, the effect of such supplementation was not studied. Assessment of BMD should be considered for patients with history of pathologic bone fracture or other risk factors for osteoporosis or bone loss. If bone abnormalities are suspected, appropriate consultation should be obtained.

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Tenofovir alafenamide (as a single ingredient product) is not recommended in patients with decompensated liver dysfunction (Child-Pugh B or C); safety and efficacy have not been established in these patients. No dose adjustment of tenofovir alafenamide is required in patients with mild liver dysfunction (Child-Pugh A).
-Combination products containing tenofovir alafenamide have not been studied in patients with severe liver dysfunction; some of these products are not recommended for use in such patients. No dose adjustment of tenofovir alafenamide-containing products is required in patients with mild or moderate liver dysfunction (Child-Pugh A or B).

The pharmacokinetics of tenofovir after a single 300 mg dose of tenofovir disoproxil fumarate (DF) have been studied in non-HIV infected subjects with moderate to severe liver dysfunction. There were no significant changes in tenofovir pharmacokinetics in subjects with liver dysfunction compared to those with normal liver function. No adjustment in tenofovir DF dosing is required in patients with liver dysfunction.

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Tenofovir is primarily eliminated by the kidneys via glomerular filtration and active tubular secretion. Serum creatinine, estimated CrCl, urine glucose, and urine protein should be assessed in all patients before/when starting tenofovir (alafenamide or disoproxil fumarate [DF]) and during therapy when clinically appropriate. Serum phosphorus should also be assessed in patients with chronic kidney disease.

Postmarketing cases of renal impairment (including acute renal failure, proximal renal tubulopathy, and Fanconi syndrome) have been reported with tenofovir alafenamide-containing products; most cases had potential confounders that may have contributed to the reported renal events and may have predisposed patients to tenofovir-related side effects. Tenofovir alafenamide should be discontinued in patients who develop clinically significant decreases in renal function or evidence of Fanconi syndrome.

Renal impairment (including acute renal failure and Fanconi syndrome) has been reported with tenofovir DF. Close monitoring of renal function and dosing interval adjustment are recommended for all patients with CrCl less than 50 mL/min. Creatinine clearance should be calculated in all patients before starting tenofovir treatment and during treatment when clinically appropriate. Routine monitoring of serum creatinine and phosphorus is recommended for patients at risk of or with a history of renal dysfunction. Safety and efficacy have not been evaluated in patients with renal dysfunction using dose adjustments; therefore, the benefit of tenofovir DF treatment should be weighed against the risk of renal toxicity. Renal function should be evaluated in patients at risk of renal dysfunction who have persistent or worsening bone pain, pain in extremities, fractures, and/or muscular pain or weakness (may be indicators of proximal renal tubulopathy).

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