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RITONAVIR

Medical Diagnosis and Drugs, Medications
RITONAVIR
(ri-ton'a-vir)
Norvir
Classifications: antiretroviral agent; protease inhibitor;
Therapeutic: antiretroviral; protease inhibitor
Prototype: Saquinavir
Pregnancy Category: B

Availability

100 mg capsules; 80 mg/mL solution

Action

HIV protease is an enzyme required to produce the polyprotein procurers of functional proteins in infectious HIV. Protease inhibitors prevent cleavage of the viral polyproteins, resulting in the formation of immature noninfectious virus particles.

Therapeutic Effect

Protease inhibitor of both HIV-1 and HIV-2 resulting in the formation of noninfectious viral particles.

Uses

Alone or in combination with other antiretroviral agents or protease inhibitors for treatment of HIV infection. Often used to increase the effect of other ANTIRETROVIRALS.

Contraindications

Hypersensitivity to ritonavir; antimicrobial resistance to protease inhibitors; pancreatitis; lactation. Safe use in children <1 mo has not been established.

Cautious Use

Pregnancy (category B); hepatic diseases, hepatic insufficiency, liver enzyme abnormalities, or hepatitis, jaundice, advanced HIV disease; diabetes mellitus, diabetic ketoacidosis, hyperglycemia, hyperlipidemia, hypertriglyceridemia; hemophilia A or B, renal insufficiency, concurrent administration with HMG-Coa reductase inhibitors.

Route & Dosage

HIV
Adult: PO 600 mg b.i.d. 1 h before or 2 h after meal (may take with a light snack)
Child (>1 mo): PO 300–400 mg/m2 b.i.d. (max: 600 mg b.i.d.), start with 250 mg/m2 b.i.d., increase by 50 mg/m2 q2–3d

Administration

Oral
  • Give preferably with food; oral solution may be mixed with chocolate milk within 1 h of dosing to improve taste.
  • Do not give concurrently with any of the following drugs: alprazolam, amiodarone, bepridil, bupropion, clozapine, clorazepate, diazepam, dihydroergotamine, ergotamine, encainide, estazolam, flecainide, flurazepam, meperidine, midazolam, piroxicam, propafenone, propoxyphene, quinidine, rifabutin, triazolam, zolpidem.
  • Store refrigerated at 2°–8° C (36°–46° F). Protect from light in tightly closed container.

Adverse Effects (≥1%)

Body as a Whole: Myalgia, allergic reaction, bronchitis, cough, rhinitis, taste alterations, visual disturbances, dysuria, hyperglycemia, diabetes. CNS: Asthenia, fatigue, headache, fever, malaise, circumoral or peripheral paresthesia, insomnia, dizziness, somnolence, abnormal thinking, amnesia, agitation, anxiety, confusion, convulsions, aphasia, ataxia, diplopia, emotional lability, euphoria, hallucinations, decreased libido, nervousness, neuralgia, neuropathy, peripheral neuropathy, paralysis, tremor, vertigo. CV: Palpitations, vasodilation, hypotension, postural hypotension, syncope, tachycardia. Hematologic: Anemia, thrombocytopenia, lymphadenopathy. GI: Nausea, diarrhea, vomiting, abdominal pain, dyspepsia, stomatitis, anorexia, dry mouth, constipation, flatulence, cholecystitis, cholestasis, abnormal liver function tests, hepatitis. Skin: Rash, sweating, acne, contact dermatitis, pruritus, urticaria, skin ulceration, dry skin.

Interactions

Drug: Carbamazepine, dexamethasone, phenobarbital, phenytoin, rifabutin, rifampin, smoking can decrease ritonavir levels. Ritonavir may increase serum levels and toxicity of clarithromycin, especially in patients with renal insufficiency (reduce clarithromycin dose in patients with Clcr <60 mL/min); desipramine; saquinavir, amiodarone, bepridil, bupropion, clozapine, dihydroergotamine, flecainide, meperidine, pimozide, piroxicam, propoxyphene, quinidine, rifabutin, trazodone, alfuzosin, fluticasone. Ritonavir decreases levels of oral contraceptives, theophylline; may increase ergotamine toxicity with dihydroergotamine, ergotamine; may increase systemic steroid exposure with fluticasone. Liquid formulation may cause disulfiram-like reaction with alcohol or metronidazole. See the complete prescribing information for a comprehensive table of potential, but not studied, drug interactions. Herbal: St. John's wort, garlic may decrease antiretroviral activity.

Pharmacokinetics

Absorption: Rapidly from GI tract. Peak: 2–4 h. Distribution: 98–99% protein bound. Metabolism: In liver (CYP3A4). Elimination: Primarily in feces (>80%).

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Monitor periodically CBC with differential and platelet count, liver function, kidney function, serum albumin, lipid profile, CPK, serum amylase, electrolytes, blood glucose HbA1C, and alkaline phosphatase.
  • Withhold drug and notify physician in the presence of abnormal liver function.
  • Assess for S&S of GI distress, peripheral neuropathy, and other potential adverse effects.

Patient & Family Education

  • Learn potential adverse reactions and drug interactions; report to physician use of any OTC or prescription drugs.
  • Take this drug exactly as prescribed. Do not skip doses. Take at same time each day.

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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