Nurses Compass
Drug Guide
Ritonavir
Classification
Therapeutic: Antiretroviral agent, Protease inhibitor
Pharmacological: Viral protease inhibitor
FDA Approved Indications
- Treatment of HIV-1 infection in combination with other antiretroviral agents
Mechanism of Action
Inhibits the HIV protease enzyme, preventing viral maturation and producing non-infectious viral particles.
Dosage and Administration
Adult: Typically 300 mg twice daily with food, in combination with other antiretrovirals.
Pediatric: Dosing varies; consult specific guidelines.
Geriatric: Adjust dose based on renal and hepatic function, caution due to comorbidities.
Renal Impairment: Use with caution; no specific dose adjustment, but renal function should be monitored.
Hepatic Impairment: Use with caution; dose adjustment may be necessary due to extensive hepatic metabolism.
Pharmacokinetics
Absorption: Well absorbed orally, food increases bioavailability.
Distribution: Widely distributed; crosses the blood-brain barrier.
Metabolism: Primarily metabolized in the liver via CYP3A4 and CYP2D6.
Excretion: Metabolites are excreted mainly in feces; minimal renal excretion.
Half Life: Approx. 3-5 hours; adjusted when given with other drugs.
Contraindications
- Use caution in patients with hypersensitivity to ritonavir or other components.
- Contraindicated with certain drugs that are CYP3A4 substrates, QT prolongation risk, or when combined with drugs that can cause torsades de pointes.
Precautions
- Hepatic impairment, especially hepatitis B or C co-infection.
- Use with caution in patients with significant cardiac disease or QT prolongation.
- Pregnancy category B—discuss potential benefits and risks.
Adverse Reactions - Common
- Gastrointestinal disturbances (nausea, vomiting, diarrhea) (Common)
- Altered taste (dysgeusia) (Common)
Adverse Reactions - Serious
- Hepatotoxicity (including hepatitis and hepatitis exacerbation) (Uncommon)
- QT prolongation and Torsades de Pointes (Rare)
- Drug hypersensitivity reactions (Rare)
Drug-Drug Interactions
- Interactions with medications metabolized by CYP3A4 (e.g., certain statins, benzodiazepines, ergot derivatives)
- Potential for increased levels of drugs like sildenafil, lidocaine, and certain antiarrhythmics.
Drug-Food Interactions
- High-fat meals increase absorption; consistency recommended.
Drug-Herb Interactions
- St. John’s Wort can significantly decrease ritonavir levels, reducing efficacy.
Nursing Implications
Assessment: Monitor liver function tests, lipid profile, and cardiac status (ECG) as needed.
Diagnoses:
- Risk for hepatotoxicity
- Risk for cardiac arrhythmias due to QT prolongation
Implementation: Administer with food, monitor for signs of hepatitis or cardiac issues, educate patient about interactions.
Evaluation: Check viral load response, monitor for adverse effects, ensure adherence.
Patient/Family Teaching
- Take exactly as prescribed, with food.
- Inform about potential side effects like gastrointestinal upset and altered taste.
- Report signs of hepatotoxicity (jaundice, dark urine) or cardiac symptoms (chest pain, dizziness).
- Avoid herbal supplements, especially St. John’s Wort.
Special Considerations
Black Box Warnings:
- Serious drug interactions resulting in adverse outcomes such as hepatic failure or cardiac arrhythmias.
- Potential for hepatotoxicity and increased bleeding in hemophilia patients.
Genetic Factors: Pharmacogenetic variations in CYP3A4 may influence drug levels.
Lab Test Interference: Can affect lipid panels, hepatic function tests.
Overdose Management
Signs/Symptoms: Nausea, vomiting, hypotension, dizziness, and possible hepatic injury.
Treatment: Supportive care; no specific antidote. Discontinue drug, monitor cardiac and hepatic function, provide symptomatic treatment.
Storage and Handling
Storage: Store at room temperature (15-30°C), protected from light and moisture.
Stability: Stable under recommended storage conditions for the duration specified in the label.