Home Drug Guide Darunavir and Ritonavir

Drug Guide

Generic Name

Darunavir and Ritonavir

Brand Names Prezcobix

Classification

Therapeutic: Antiretroviral (HIV-1 protease inhibitor combination)

Pharmacological: Protease inhibitor with CYP3A4 inhibitor

FDA Approved Indications

Treatment of HIV-1 infection

Mechanism of Action

Darunavir inhibits the HIV-1 protease enzyme, preventing viral maturation. Ritonavir inhibits CYP3A4, boosting darunavir levels by decreasing its metabolism.

Dosage and Administration

Adult: 600 mg darunavir with 100 mg ritonavir once daily or 800 mg darunavir with 100 mg ritonavir twice daily, taken with food.

Pediatric: Not generally approved for pediatric use.

Geriatric: No specific dosing adjustments recommended; consider renal and hepatic function.

Renal Impairment: Use with caution; no specific dose adjustment provided.

Hepatic Impairment: Adjust dose in moderate to severe hepatic impairment; specific guidelines not established.

Pharmacokinetics

Absorption: Well absorbed orally, enhanced by food.

Distribution: Widely distributed in tissues; protein binding approx. 95%.

Metabolism: Metabolized primarily by CYP3A4; ritonavir inhibits CYP3A4 to boost levels.

Excretion: Primarily fecal, minimal renal excretion.

Half Life: Darunavir: approximately 15 hours; ritonavir: approximately 3-5 hours.

Contraindications

Hypersensitivity to darunavir, ritonavir, or excipients.
Use with drugs highly dependent on CYP3A4 for clearance and with known interactions.

Precautions

Use with caution in hepatic impairment.
Monitor for hepatotoxicity and hypersensitivity reactions.
Consider resistance testing for HIV.

Adverse Reactions - Common

Nausea (Common)
Headache (Common)
Diarrhea (Common)
Rash (Common)

Adverse Reactions - Serious

Drug hypersensitivity reactions including Stevens-Johnson syndrome (Rare)
Hepatotoxicity (Uncommon)
Lipodystrophy and metabolic disturbances (Less common)

Drug-Drug Interactions

Strong CYP3A4 inhibitors and inducers, certain statins, antiarrhythmics, sedatives, ergot derivatives.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor liver function tests, lipid profile, and signs of hypersensitivity.

Diagnoses:

Risk for hepatotoxicity
Impaired comfort related to gastrointestinal side effects.

Implementation: Administer with food, monitor labs regularly, educate on adherence and side effect reporting.

Evaluation: Assess viral load suppression, monitor for adverse effects, evaluate liver function.

Patient/Family Teaching

Take medication with food to enhance absorption.
Report any signs of allergic reactions or liver problems.
Do not discontinue without consulting healthcare provider.
Be aware of potential drug interactions.

Special Considerations

Black Box Warnings:

Serious liver injury and drug interactions.
Potential for exacerbation of hepatitis B virus—monitor for hepatitis B reactivation.

Genetic Factors: Genotypic resistance testing recommended before initiation.

Lab Test Interference: May cause elevations in liver enzymes, lipid levels, and blood sugar.

Overdose Management

Signs/Symptoms: Nausea, vomiting, hypersensitivity reactions.

Treatment: Supportive care, symptomatic treatment, contact poison control.

Storage and Handling

Storage: Store at room temperature between 20°C to 25°C (68°F to 77°F), away from moisture and light.

Stability: Stable under recommended storage conditions.