INVIRASE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for INVIRASE (INVIRASE).
Saquinavir is a selective, competitive, reversible inhibitor of the HIV-1 protease, preventing cleavage of viral polyprotein precursors into functional proteins in infected cells, resulting in the formation of immature, non-infectious viral particles.
| Metabolism | Primarily hepatic via CYP3A4; saquinavir is extensively metabolized, and co-administration with strong CYP3A4 inhibitors (e.g., ritonavir) is required to achieve therapeutic plasma concentrations. |
| Excretion | Primarily hepatic metabolism via CYP3A4, with ~1-2% excreted unchanged in urine and ~81% in feces. Renal elimination of unchanged drug is minimal (<3%). |
| Half-life | Terminal elimination half-life is approximately 1.5-2 hours, but due to potent CYP3A4 inhibition, it is often coadministered with ritonavir, which increases half-life to about 3-5 hours (effective half-life with boosting). |
| Protein binding | ~98-99% bound to human serum albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.44 L/kg (range 0.25-0.76 L/kg), indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability is low and variable, approximately 4% (range 1-8%) without ritonavir boosting; coadministration with ritonavir increases bioavailability to about 8-20%. |
| Onset of Action | Oral administration: Onset is within 1-2 hours, reaching peak plasma concentrations at about 4 hours post-dose. |
| Duration of Action | With ritonavir boosting, trough concentrations remain above IC95 for 12 hours, allowing twice-daily dosing. Without boosting, duration is short (approximately 6-8 hours) due to rapid clearance. |
1000 mg orally twice daily boosted with ritonavir 100 mg orally twice daily or 1500 mg orally once daily boosted with ritonavir 100 mg orally once daily.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl ≥30 mL/min). For severe renal impairment (CrCl <30 mL/min), use is not recommended due to lack of data. |
| Liver impairment | Child-Pugh Class A: No dose adjustment. Child-Pugh Class B: Caution, reduce dose to 600 mg orally three times daily boosted with ritonavir. Child-Pugh Class C: Contraindicated. |
| Pediatric use | For children ≥2 years and weighing ≥10 kg: 50 mg/kg/dose orally twice daily (maximum 1000 mg/dose) boosted with ritonavir (3 mg/kg/dose twice daily, maximum 100 mg/dose). For children <2 years: Not recommended. |
| Geriatric use | No specific dose adjustment recommended. Monitor renal function and potential drug interactions due to age-related decline in organ function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for INVIRASE (INVIRASE).
| Breastfeeding | Saquinavir is excreted in human breast milk at low concentrations (M/P ratio unknown); potential for HIV transmission in breast milk contraindicates breastfeeding in HIV-positive women regardless of therapy. |
| Teratogenic Risk | First trimester: Limited human data, but no increased risk of major birth defects observed in small studies; animal studies show no teratogenicity at systemic exposures similar to human. Second and third trimesters: No specific fetal risks identified; use only if benefit outweighs potential risk due to lack of adequate data. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to saquinavir or any component of the formulation.","Concomitant use with drugs that are highly dependent on CYP3A4 for clearance and for which elevated plasma concentrations are associated with serious/life-threatening events (e.g., alfuzosin, amiodarone, bepridil, ergot derivatives, lovastatin, simvastatin, midazolam oral, pimozide, quetiapine, sildenafil when used for pulmonary arterial hypertension, triazolam, cisapride, lurasidone, ranolazine, avanafil).","Concomitant use with strong CYP3A4 inducers (e.g., rifampin, St. John's wort, carbamazepine, phenobarbital, phenytoin) due to risk of loss of virologic response.","Concomitant use with PPIs (e.g., omeprazole, esomeprazole, lansoprazole, dexlansoprazole, pantoprazole, rabeprazole) is not recommended due to significant decrease in saquinavir concentrations.","Patients with congenital or acquired QT prolongation (QTc >450 ms for men, >470 ms for women).","Patients with complete atrioventricular block without implanted pacemaker."]
| Precautions | ["Hepatotoxicity: Monitor hepatic function; discontinue if signs of hepatitis or transaminase elevation with bilirubin >2x ULN.","PR interval prolongation: Use with caution in patients with pre-existing conduction abnormalities or concurrent use of drugs that prolong PR interval; monitor ECG.","QT interval prolongation: Avoid use in patients with history of QT prolongation or with drugs known to prolong QT; correct electrolyte abnormalities before initiating.","Hyperglycemia/diabetes mellitus: Monitor blood glucose; new-onset diabetes or exacerbation may occur.","Increased bleeding in hemophiliacs: Spontaneous hematomas may occur in patients with hemophilia A or B.","Fat redistribution: Accumulation of central obesity, dorsocervical fat (buffalo hump), peripheral wasting, breast enlargement, and cushingoid appearance.","Immune reconstitution syndrome: During initial treatment, inflammatory response to indolent or residual opportunistic infections may occur (e.g., Mycobacterium avium, CMV, PCP).","Hyperlipidemia: Monitor triglycerides and cholesterol; manage as clinically appropriate.","Pancreatitis: Discontinue if signs/symptoms (nausea, vomiting, abdominal pain) with elevated lipase/amylase."] |
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| Fetal Monitoring |
| Monitor maternal liver function tests, serum triglycerides, cholesterol, and blood glucose regularly; fetal ultrasound for growth and development if used during pregnancy. |
| Fertility Effects | No negative effects on fertility reported in animal studies; no human data available. |