ADEFOVIR DIPIVOXIL

ADEFOVIR DIPIVOXIL
(a-de'fo-vir)
Hepsera
Classifications: antiviral agent; nucleotide analog;
Therapeutic: antiviral

Pregnancy Category: C

Availability

10 mg tablets

Action

Inhibits human hepatitis virus (HBV) DNA polymerase (reverse transcriptase) by competing with its DNA and by causing DNA chain termination after its incorporation into viral DNA. This results in inhibition of HBV DNA replication.

Therapeutic Effect

A nucleotide analog with activity against human hepatitis B virus (HBV).

Uses

Treatment of chronic hepatitis B.

Contraindications

Hypersensitivity to adefovir; untreated or unknown human immunodeficiency virus (HIV); exacerbations of hepatitis B, especially in patients who have discontinued anti-hepatitis B therapy; pregnancy (category C); lactation. Safety and efficacy in children are not established.

Cautious Use

Decreased cardiac function due to concomitant disease or other drug therapy; elderly; concomitant use of highly nephrotoxic drugs; renal dysfunction; co-administration with drugs that reduce renal function or compete for active tubular secretion. Appropriate infant immunizations should be used to prevent neonatal acquisition of the hepatitis B virus.

Route & Dosage

Hepatitis B
Adult: PO 10 mg q.d.

Renal Impairment
Clcr 20–49 mL/min: 10 mg q48h; 10–19 mL/min: 10 mg q72h
Hemodialysis: 10 mg q7d following dialysis

Administration

Oral
  • Note that the dosing interval of adefovir should be adjusted in patients with baseline creatinine clearance <50 mL/min.
  • Store in original container at 15°–30° C (59°–86° F).

Adverse Effects (≥1%)

CNS: Asthenia, headache. GI: Abdominal pain, nausea, flatulence, diarrhea, dyspepsia, exacerbation of hepatitis after discontinuation of therapy, hepatomegaly. Metabolic: Increased ALT, AST, increased creatine kinase, amylase, lactic acidosis. Urogenital: Hematuria, glycosuria, increased serum creatinine, nephrotoxicity. Other: HIV resistance in patient with unrecognized HIV, hematuria.

Interactions

Drug: Risk of lactic acidosis when used with nucleoside analogs. Ibuprofen increases bioavailability of adefovir.

Pharmacokinetics

Absorption: Adefovir dipivoxil is a prodrug. 59% of dose is absorbed as active drug. Peak: 1–4 h. Distribution: Minimal protein binding. Metabolism: Adefovir dipivoxil is rapidly converted to active adefovir. Elimination: Primarily in urine. Half-Life: 7.5 h.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Monitor baseline and periodic renal function tests (monitor more often with pre-existing impairment or other risk factors for renal impairment); monitor periodic liver function tests, creatinine kinase, serum amylase, and routine blood chemistries including serum electrolytes.
  • Withhold drug and notify physician if lactic acidosis is suspected [e.g., hyperventilation, lethargy, plasma pH <7.35 and lactate >5–6 mol/L (mEq/L)].

Patient & Family Education

  • Report any of the following to physician: blood in urine, unexplained weakness, or exacerbation of S&S of hepatitis.
  • Patients who discontinue adefovir should be monitored at repeated intervals over a period of time for hepatic function.

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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