tenofovir disoproxil fumarate

tenofovir disoproxil fumarate,

a prodrug of tenofovir, used in the treatment of HIV-1 (human immunodeficiency virus-1) infection.

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tenofovir disoproxil fumarate

Viread

Pharmacologic class: Nucleoside analog reverse transcriptase inhibitor

Therapeutic class: Antiretroviral

Pregnancy risk category B

FDA Boxed Warning

• Lactic acidosis and severe hepatomegaly with steatosis (including fatal cases) have occurred with use of drug alone or in combination with other antiretrovirals. Drug isn't indicated to treat chronic hepatitis B virus (HBV) infection. Its safety and efficacy aren't established in patients coinfected with HBV and human immunodeficiency virus (HIV). Severe acute HBV exacerbations have occurred in patients with such coinfections who've discontinued therapy; in these patients, monitor hepatic function closely with both clinical and laboratory follow-up for at least several months.

Action

Inhibits activity of HIV by competing with natural substrate deoxyadenosine 5'-triphosphate; disrupts cellular DNA by causing chain termination

Availability

Tablets: 300 mg

⊘Indications and dosages

➣ HIV-1 infection

Adults: 300 mg P.O. daily

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug
• Renal insufficiency
• Hepatotoxicity
• Lactic acidosis
• Breastfeeding

Precautions

Use cautiously in:
• elderly patients
• pregnant patients
• children.

Administration

• Give without regard to meals.
• Know that drug is usually given with other antiretrovirals. If patient is also receiving didanosine, give tenofovir at least 2 hours before or 1 hour after didanosine.

Route	Onset	Peak	Duration
P.O.	Rapid	45-75 min	Unknown

Adverse reactions

CNS: headache, asthenia

GI: nausea, vomiting, diarrhea, abdominal pain, flatulence, anorexia

GU: glycosuria

Hepatic: severe hepatomegaly with steatosis

Metabolic: hyperglycemia, lactic acidosis

Other: body fat redistribution

Interactions

Drug-drug. Acyclovir, cidofovir, didanosine, ganciclovir, indinavir, iopinavir, probenecid, ritonavir, valacyclovir, valganciclovir, other drugs eliminated by active tubular secretion: increased blood level of either drug

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 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 once daily with or without food.
• If patient is also receiving didanosine, instruct him to take tenofovir at least 2 hours before or 1 hour after didanosine.
☞ 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.