Ritonavir

A to Z Drug Facts

  Action Inhibits human immunodeficiency virus (HIV) protease, the enzyme required to form functional proteins in HIV-infected cells.

  Indications Treatment of HIV infection. May be given in combination with nucleoside analogs (eg, zidovudine) or as monotherapy.

  Contraindications Concomitant therapy with amiodarone, bepridil, bupropion, cisapride, clozapine, encainide, flecainide, meperidine, pimozide, piroxicam, propafenone, propoxyphene, quinidine, and rifabutin. Coadministration of alprazolam, clorazepate, diazepam, ergot derivatives, estazolam, flurazepam, midazolam, triazolam, and zolpidem.

  Route/Dosage

ADULTS: PO 600 mg bid. If nausea occurs, relief may be provided by dose titration: 300 mg bid for 1 day, 400 mg bid for 2 days, 500 mg bid for 1 day, then 600 mg bid.

CHILDREN GREATER THAN OR EQUAL TO 2 yr: PO Start at 250 mg/m² bid and increase dose at 2- to 3-day intervals by 50 mg/m² bid (max, 600 mg bid).

  Interactions

Amiodarone, Bepridil, Bupropion, Cisapride, Clarithromycin, Clozapine, Encainide, Flecainide, Meperidine, Piroxicam, Propafenone, Propoxyphene, Quinidine, Rifabutin, Sildenafil: Ritonavir may elevate blood levels of these drugs, which may increase the risk of arrhythmias, hematologic abnormalities, seizures, or other potential serious adverse effects.

Alprazolam, Clorazepate, Diazepam, Estazolam, Fentanyl, Flurazepam, Midazolam, Triazolam, Zolpidem: Ritonavir may increase blood levels of these drugs, which may produce extreme sedation and respiratory depression. Do not coadminister.

Azole Antifungal Agents (eg, Ketoconazole), Clarithromycin, Interleukins: May elevate ritonavir plasma levels, increasing the risk of side effects.

Carbamazepine, Dexamethasone, Phenobarbital, Phenytoin, Rifabutin, Rifampin, St. John’s Wort: May decrease plasma concentrations of ritonavir.

Desipramine: Desipramine levels may be increased.

Didanosine, Methadone, Theophylline: Levels may be decreased by ritonavir.

Disulfiram, Metronidazole: Ritonavir contains alcohol and may produce a disulfiram-like reaction with these drugs.

Ergot Derivatives (eg, Ergotamine): Because the risk of ergot toxicity may be increased, coadministration with ritonavir is contraindicated.

Oral Contraceptives: Concentrations of ethinyl estradiol, a component of oral contraceptives, may be reduced.

Saquinavir: Ritonavir may inhibit indinavir and saquinavir metabolism and increase their levels.

Warfarin: The risk of bleeding may be increased.

  Lab Test Interferences None well documented.

  Adverse Reactions

CARDIOVASCULAR: Vasodilation; hemorrhage; hypotension; palpitations, postural hypotension; tachycardia. CNS: Headache; malaise; circumoral paresthesia; paresthesia; dizziness; insomnia; somnolence; abnormal thinking. DERMATOLOGIC: Rash; swelling. EENT: Pharyngitis; sore throat; abnormal taste. GI: Anorexia; constipation; diarrhea; dyspepsia; flatulence; nausea; vomiting; abdominal pain. GU: Impotence; dysuria; kidney failure. HEPATIC: Hepatitis; hepatomegaly; abnormal LFTs. METABOLIC: Increased CPK; hyperlipidemia; diabetes mellitus. OTHER: Asthenia; fever; myalgia.

  Precautions

Pregnancy: Category B. Lactation: Undetermined. HIV-infected mothers should not breastfeed their infants. Children: Not recommended for children less than 2 yr. Hepatic Function Impairment: Use caution; decreased ritonavir clearance may occur.

  Administration/Storage

• The medication should be taken with food.
• The oral solution may be mixed with chocolate milk, Ensure, or Advera within 1 hr of dosing to improve the taste.
• Store capsules in the refrigerator in a light-resistant container.
• Store oral solution in refrigerator until opened. It may be stored at room temperature after opening if used within 30 days. Keep in original container with cap tightly closed.
• Do not switch between oral solution and capsules, as the absorption rates are different.

  Assessment/Interventions

• Obtain patient history.
• Assess for history of impaired hepatic function. This medication is metabolized in, and toxic to, the liver.
• Obtain baseline triglycerides, ALT, AST, GGT, CPK, and uric acid. Monitor periodically during treatment.
• Monitor WBC and differential. Note any significant changes.
• Monitor Hct and Hgb frequently (severe anemia may require blood transfusions).

  Patient/Family Education

• Advise patient to take ritonavir with food.
• Advise patient to take medication exactly as prescribed.
• Warn patient not to alter the dose or discontinue the medication without consulting health care provider.
• If patient misses a dose, take the next dose as soon as possible. If a dose is skipped, do not double the next dose.
• Instruct patient not to take any other medications, including otc medications, without checking with their health care provider first. This medication interacts with a wide range of all types of medications.
• Explain that the patient will be required to have frequent follow-up blood and urine tests during the course of the treatment and to keep appointments.
• Inform patient that this medication is not a cure for HIV infection and they may continue to acquire secondary illnesses associated with the disease.
• Emphasize to patient, family, and significant others that this medication does not reduce the risk of transmitting HIV to others through sexual contact or blood contamination.
• Inform patient to report symptoms associated with paresthesia (eg, sensations of burning, prickling, formication) to health care provider for a possible reduction in dosage.
• Inform patient to report any other serious side effects to health care provider.
• Explain that the long-term effects of this medication are not known at this time.

Books@Ovid
Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts