TENOFOVIR DISOPROXIL FUMARATE

TENOFOVIR DISOPROXIL FUMARATE
(ten-o-fo'vir di-so-prox'il fum'a-rate)
Viread
Classifications: antiretroviral agent; nucleoside reverse transcriptase inhibitor (nrti);
Therapeutic: antiretroviral; nrti

Prototype: Zidovudine
Pregnancy Category: B

Availability

300 mg tablets

Action

Tenofovir is a potent inhibitor of retroviruses, including HIV-1. It may be active against nucleoside-resistant HIV strains. The active form of tenofovir persists in HIV-infected cells for prolonged periods, thus, it results in sustained inhibition of HIV replication.

Therapeutic Effect

It reduces the viral load (plasma HIV-RNA), and CD4 counts.

Uses

In combination with other antiretrovirals for the treatment of HIV.

Contraindications

Hypersensitivity to tenofovir; hepatitis; lactic acidosis; concurrent administration of nephrotoxic agents, renal failure; lactation.

Cautious Use

Hepatic dysfunction, alcoholism; renal impairment; obesity; children, pregnancy (category B).

Route & Dosage

HIV Infection
Adult: PO 300 mg once daily with meal

Renal Impairment
Clcr 30–49 mL/min: dose q48h, 10–29 mL/min dose twice weekly
Hemodialysis: Dose weekly or after 12 h of dialysis

Administration

Oral
  • Give at the same time each day with a meal.
  • Give 2 h before or 1 h after didanosine (if ordered concurrently).
  • Store at room temperature; excursions to 15°–30° C (59°–80° F) are permitted.

Adverse Effects (≥1%)

Body as a Whole: Asthenia. CNS: Headache. GI: Nausea, vomiting, diarrhea, flatulence, abdominal pain, anorexia. Hematologic: Neutropenia. Metabolic: Increased creatine kinase, AST, ALT, serum amylase, triglycerides, serum glucose.

Interactions

Drug: May increase didanosine toxicity; acyclovir, amphotericin B, cidofovir, foscarnet, ganciclovir, probenecid, valacyclovir, valganciclovir may increase tenofovir toxicity by decreasing its renal elimination. Food: Food increases absorption.

Pharmacokinetics

Absorption: Bioavailability 25% fasting, 40% with high fat meal. Peak: 1 h. Distribution: <7% protein bound. Metabolism: Not metabolized by CYP450 enzyme system. Elimination: Renally eliminated. Half-Life: 11–14 h.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Monitor baseline and periodic renal function and LFTs; monitor periodically serum electrolytes, and ABGs if lactic acidosis is suspected.
  • Monitor for S&S of bone abnormalities (e.g., bone pain, stress fractures).
  • Monitor closely patients receiving other nephrotoxic agents for changes in serum creatinine and phosphorus. Withhold drug and notify physician for creatinine clearance <60 mL/min.
  • Withhold drug and notify physician if patient develops clinical or lab findings suggestive of lactic acidosis or pronounced hepatotoxicity (e.g., hepatomegaly and steatosis even in the absence of marked transaminase elevations).

Patient & Family Education

  • Take this drug exactly as prescribed. Do not miss any doses. If you miss a dose, take it as soon as possible and then take your next dose at its regular time. If it is almost time for your next dose, do not take the missed dose. Wait and take the next dose at the regular time. Do not double the next dose.
  • Report any of the following to physician: unexplained anorexia, nausea, vomiting, abdominal pain, fatigue, dark urine.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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