tenofovir disoproxil fumarate
tenofovir disoproxil fumarate
Pharmacologic class: Nucleoside analog reverse transcriptase inhibitor
Therapeutic class: Antiretroviral
Pregnancy risk category B
FDA Box Warning
Severe acute exacerbations of hepatitis have been reported in patients with hepatitis B virus (HBV) infection who have discontinued anti-hepatitis B therapy. Monitor hepatic function closely with both clinical and laboratory follow-up for at least several months in patients who discontinue anti-hepatitis B therapy. If appropriate, resumption of anti-hepatitis B therapy may be warranted.
Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs, including tenofovir.
Drug should not be given with adefovir dipivoxil.
Because of risk of development of human immunodeficiency virus-1 (HIV-1) resistance, drug should only be used in HIV-1 and HBV co-infected patients as part of an appropriate antiretroviral combination regimen.
HIV-1 antibody testing should be offered to all HBV-infected patients before start of therapy. It is also recommended that all patients with HIV-1 infection be tested for presence of chronic HBV infection before start of drug therapy.
Drug's effects on bone haven't been studied in patients with chronic HBV infection.
In HIV-infected patients, redistribution or accumulation of body fat, including central obesity, dorsocervical fat enlargement (buffalo hump), peripheral wasting, facial wasting, breast enlargement, and cushingoid appearance, has been observed in patients receiving combination antiretroviral therapy.
Immune reconstitution syndrome has been reported in HIV-infected patients treated with combination antiretroviral therapy.
Action
Inhibits activity of HIV by competing with natural substrate deoxyadenosine 5'-triphosphate; disrupts cellular DNA by causing chain termination
Availability
Powder, oral: 40 mg/scoop
Tablets: 150 mg, 200 mg, 250 mg, 300 mg
Indications and dosages
➣ HIV-1 infection, chronic hepatitis B infection
Adults and adolescents age 12 and older weighing 35 kg (77 lb) or more: 300 mg P.O. daily; for patients unable to swallow tablets, give 7.5 scoops of oral powder.
➣ HIV-1 infection
Children ages 2 to younger than 12: 8 mg/kg (to maximum of 300 mg) P.O. once daily as oral powder or tablets
Dosage adjustment
• Baseline creatinine clearance less than 50 ml/minute
Contraindications
• None
Precautions
Use cautiously in:
• renal impairment
• lactic acidosis
• exacerbation of hepatitis, hepatomegaly with steatosis
• co-administration of adefovir dipivoxil or other tenofovir-containing products
• concurrent or recent use of nephrotoxic drugs.
• decreased bone marrow density
• redistribution or accumulation of body fat
• immune reconstitution syndrome
• elderly patients
• pregnant or breastfeeding patients
• children younger than age 2 with HIV-1 infection and younger than age 12 or less than 35 kg (77 lb) with chronic hepatitis B infection (safety and efficacy not established).
Administration
• Assess creatinine clearance before starting drug.
• Give tablets without regard to meals.
• Give oral powder with 2 to 4 oz of soft foods that can be swallowed without chewing (such as applesauce, baby food, or yogurt). Don't mix with liquids. Give dose immediately after mixing.
• Know that drug is usually given with other antiretrovirals for HIV infection.
Adverse reactions
CNS: headache, asthenia, depression
GI: nausea, vomiting, diarrhea, abdominal pain, flatulence, anorexia
GU: new-onset or worsening renal impairment (including acute renal failure and Fanconi syndrome)
Skin: rash
Hepatic: severe hepatomegaly with steatosis
Metabolic: hyperglycemia, lactic acidosis
Other: body fat redistribution, pain, immune reconstitution syndrome
Interactions
Drug-drug. Acyclovir, cidofovir, didanosine, ganciclovir, indinavir, lopinavir, probenecid, ritonavir, valacyclovir, valganciclovir, other drugs eliminated by active tubular secretion (such as adefovir dipivoxil): increased blood level of either drug
Atazanavir, lopinavir/ritonavir: increased tenofovir concentration
Drug-diagnostic tests. Alanine aminotransferase, amylase, aspartate aminotransferase, blood and urine glucose, creatine kinase, triglycerides: increased levels
Neutrophils: decreased count
Drug-food. Any food: decreased drug bioavailability and efficacy
Patient monitoring
Watch for and report signs and symptoms of lactic acidosis or hepatotoxicity.
• Monitor bone mineral density in patients with history of pathologic fractures or who are at risk for osteopenia.
Monitor for signs of immune reconstitution syndrome, especially during initial phase of combination antiretroviral treatment when patients whose immune systems respond may develop an inflammatory response to indolent or residual opportunistic infections (such as Mycobacterium avium infection, cytomegalovirus, Pneumocystis jiroveci pneumonia, or tuberculosis), which may necessitate further evaluation and treatment.
• Monitor kidney and liver function tests.
• Assess nutritional status and hydration in light of adverse GI reactions and underlying disease.
Patient teaching
• Tell patient to take tablets once daily at the same time every day with or without food and take oral powder at the same time every day with food.
• Tell patient not to mix oral powder with liquids. Tell patient to use only the dosing scoop supplied, to mix only with 2 to 4 oz of soft foods that can be swallowed without chewing (such as baby food, applesauce, or yogurt), and to take entire dose immediately after mixing.
Instruct patient to immediately report unusual tiredness or yellowing of skin or eyes.
• Tell patient drug may cause weakness and headache. Caution him to avoid driving and other hazardous activities until he knows how drug affects performance.
• Caution female patient not to breastfeed.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and foods mentioned above.