DIDANOSINE (DDI)

DIDANOSINE (DDI)
(di-dan'o-sine)
Videx, Videx EC
Classifications: antiretroviral agent; nucleoside reverse transcriptase inhibitor (nrti);
Therapeutic: antiviral; antiretroviral (nrti)
Prototype: Lamivudine
Pregnancy Category: B

Availability

25 mg, 50 mg, 100 mg, 150 mg, 200 mg tablets; 125 mg, 200 mg, 250 mg, 400 mg delayed release capsules; 100 mg, 167 mg, 250 mg, 2 g, 4 g powder for oral solution

Action

DDI interferes with the HIV RNA-dependent DNA polymerase (reverse transcriptase), thus preventing replication of the virus.

Therapeutic Effect

Synthetic purine nucleotide that inhibits replication of HIV.

Uses

Advanced HIV infection in patients who are intolerant to zidovudine (AZT) or who demonstrate significant clinical or immunological deterioration during zidovudine therapy.

Contraindications

Hypersensitivity to any of the components in the formulation; pancreatitis; PKU; lactation.

Cautious Use

Individuals with peripheral vascular disease, history of neuropathy, chronic pancreatitis, renal impairment, or any liver impairment; patients on sodium restriction; renal failure, renal impairment; alcoholism; elderly; gout; pregnancy (category B).

Route & Dosage

HIV Infection
Adult: PO <60 kg, tablets, 250 mg q.d. or 125 mg b.i.d. (take 2 tablets at each dose to ensure adequate buffering); <60 kg, powder, 167 mg b.i.d.; ≥60 kg, tablets, 400 mg q.d. or 200 mg b.i.d.; ≥60 kg, powder, 250 mg b.i.d.
Child: PO 120 mg/m² b.i.d., <1 y, give a 1-tablet dose; >1 y, give a 2-tablet dose

Administration

Oral

Give drug on an empty stomach. Food should not be consumed within 15–30 min of drug administration.
Give with water. Do NOT give with fruit juice or any other acid-containing liquid.
Chewable tablets must be thoroughly chewed or crushed and dispersed in at least 30 mL (1 oz) of water and immediately swallowed.
Mix powder for oral solution (buffered) with at least 120 mL (4 oz) of water, stir until dissolved (requires 2–3 min), and immediately swallowed.
Note: Powder for oral solution (pediatric) is prepared by pharmacist to yield a concentration of 10 mg/mL. Shake solution thoroughly before administration.
Dosage reduction may be indicated in those with renal or hepatic impairment.
Store reconstituted liquid in a tightly closed container in refrigerator for up to 30 d.

Adverse Effects (≥1%)

CV: Pal- pitations, thrombophlebitis, arrhythmias, vasodilation. CNS: Headache, dizziness, nervousness, insomnia, peripheral neuropathy, lethargy, poor coordination, seizures. Special Senses: Retinal depigmentation, photophobia, blurred vision, optic neuritis, diplopia, blindness. GI: Abdominal pain, nausea, vomiting, diarrhea, constipation, stomatitis, dry mouth, pancreatitis, increased liver enzymes. Hematologic: Increased WBC, neutrophil, lymphocyte, and platelet counts; increased Hgb, thrombocytopenia, ecchymosis, hemorrhage, petechiae. Metabolic: Hypocalcemia, hypokalemia, hypomagnesemia, hyperuricemia (asymptomatic), hypertriglyceridemia. Musculoskeletal: Muscle atrophy, myalgia, arthritis, decreased strength. Respiratory: Asthma, cough, dyspnea, epistaxis, rhinitis, rhinorrhea, hypoventilation, pharyngitis, rhonchi or rales, sinusitis, congestion. Skin: Rash, impetigo, eczema, pruritus, sweating, erythema.

Interactions

Drug: aluminum- and magnesium-containing antacids may increase the aluminum- and magnesium-associated adverse effects of tablets. The effectiveness of dapsone in prophylaxis of Pneumocystis carinii pneumonia may be reduced by concomitant didanosine. May cause additive neuropathy with zalcitabine (ddC). Food: Absorption is significantly decreased by food. Take on an empty stomach.

Pharmacokinetics

Absorption: Rapidly absorbed from GI tract when administered to fasting patient with antacids; 23–40% reaches systemic circulation. Peak: 0.6–1 h. Distribution: Distributed primarily to body water; 21% reaches CSF; crosses placenta. Elimination: 36% in urine. Half-Life: 0.8–1.5 h.

Nursing Implications

Assessment & Drug Effects

Monitor for S&S of pancreatitis (e.g., abdominal pain, nausea, vomiting, elevated serum amylase). Report immediately to physician and withhold drug until ruled out.
Monitor for S&S of peripheral neuropathy (e.g., numbness, tingling, burning, pain in hands or feet). Report to physician; dose reduction may be indicated.
Monitor patients with renal impairment for drug toxicity and hypermagnesemia manifested by muscle weakness and confusion.

Patient & Family Education

Report immediately to physician any of the following: Abdominal pain, nausea, or vomiting.

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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