II. Indications
- Used at low dose to "boost" most of the Protease Inhibitors
III. Mechanism
IV. Medications
- Most Protease Inhibitors are "boosted" with either Ritonavir or Cobicistat (Tybost)
- Ritonavir (Norvir) used at low dose in combination with other Protease Inhibitors
- Ritonavir at high standard dose is limited by adverse gastrointestinal effects
- Suffix '/r' added when a protease inhibutor is combined with Ritonavir
- Examples of Combinations with Ritonavir
- Formulations
- Tablets or Capsules: 100 mg
- Oral Powder: 100 mg/packet
- Oral Solution: 80 mg/ml
- Ritonavir solution contains Alcohol and propylene glycol
- Risk of propylene glycol and Alcohol Toxicity in infants age <6 months (esp <4 weeks)
- With Feeding Tube administration, use only silicone or PVC
- Avoid polyurethane tubing due to Alcohols in solution
V. Dosing: Adult
- Take with food
- Anticipate bad taste (Mix with Chocolate milk)
- Boosting dose (added to other Protease Inhibitors)
- Typical boosting dose: 100 mg daily
- Boosting Doses as high as 400 mg twice daily have been used in some protocols
- Full dose (non-boosting)
- Take 600 mg orally twice daily
- Full dose is not typically used due to adverse effects (esp. gastrointestinal)
VI. Dosing: Child
- See specific dosing protocols in which Ritonavir is used as the boosting agent
VII. Adverse Effects
- Adverse effects reflect Ritonavir used at full dose
- Adverse effects are less common with the lower, "boosting dose"
- Gastrointestinal (adverse effects may limit medication use)
- Asthenia
- Paresthesias (Circumoral or peripheral)
- Pancreatitis
- Triglycerides elevated
-
Liver Function Tests
- Cholestatic enzymes elevated
- Hepatic transaminases elevated
- Electrocardiogram changes
VIII. Safety
- Avoid in Lactation
- Pregnancy
- Pregnancy registry exists
- Frequently used in pregnancy added in low dose to other Protease Inhibitors
IX. Drug Interactions
- Multiple Drug Interactions
- See Protease Inhibitor
- Ritonavir, even at its lower boosting dose, has numerous Drug Interactions
- As with other Protease Inhibitors, check a formal Drug Interaction application before prescribing
- Many contraindicated drugs (do not coadminister)
- Check a formal Drug Interaction application before prescribing
- Examples include Amiodarone, Flecainide, Propafenone, Quinidine, rivaroxiban
-
Oral Contraceptives (OCP)
- Decreased OCP effectiveness
- Use backup or alternative Contraception
-
Voriconazole
- Ritonavir (esp. at 400 mg twice daily) decreases Voriconazole levels and efficacy
- Avoid concurrent use if possible
- Opioids
-
Clarithromycin
- Decrease Clarithromycin dose if Creatinine Clearance <60 ml/min
-
Didanosine
- Didanosine is buffered with decreased Ritonavir oral absorption
- Take Ritonavir at least 2.5 hours before or after Didanosine
-
Digoxin
- Ritonavir may increase Digoxin levels
X. Efficacy
- Very effective when "boosting" other Protease Inhibitors
XI. Resources
Images: Related links to external sites (from Bing)
Related Studies
| ritonavir (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| RITONAVIR 100 MG TABLET | Generic | $1.08 each |
| norvir (on 4/20/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| NORVIR 100 MG TABLET | Generic | $1.08 each |