Adult: To enhance the efficacy of other protease inhibitors: 100-200 mg once daily or bid.
Oral HIV infection
Adult: In combination w/ other antiretrovirals:
Initially, 300 mg bid for 3 days, increased gradually by 100 mg bid over a
period of up to 14 days. Max: 600 mg bid. Child: ≥2 yr In combination w/ other antiretrovirals: Initially, 250 mg/m2 bid, increase dose by 50 mg/m2 bid at 2-3 day intervals up to 350-400 mg/m2 bid. Max: 600 mg bid.
Administration
film-coated tab: Should be taken with food. Swallow whole, do not chew/break/crush. oral powd: Should be taken with food. May be mixed w/ soft food (eg, applesauce, vanilla pudding), water, chocolate milk or infant formula. oral soln: Should be taken with food. May be mixed w/ chocolate milk w/in 1 hr of dosing.
Contraindications
Hypersensitivity. Decompensated liver disease. Lactation. Concomitant admin w/ α1-adrenoreceptor antagonist (alfuzosin), analgesics (pethidine, piroxicam, dextropropoxyphene), antiarrhythmics (encainide, amiodarone, bepridil, flecainide, quinidine, propafenone), antihistamines (astemizole and terfenadine), antibacterial (fusidic acid), antipsychotics/neuroleptics (clozapine, pimozide, quetiapine), sedatives and hypnotics (clorazepate, diazepam, estazolam, flurazepam, triazolam, oral midazolam), ergot derivatives (ergotamine, dihydroergotamine, ergonovine, methylergonovine), statins (lovastatin, simvastatin), phosphodiesterase type 5 (PDE5) inhibitors [avanafil, sildenafil (when used for the treatment of pulmonary arterial HTN), vardenafil], GI motility agent (cisapride), voriconazole (ritonavir dose ≥400 mg bid), rifabutin (ritonavir dose of 600 mg bid), St John’s wort.
Special Precautions
Patient w/ ischaemic heart disease, cardiomyopathy, pre-existing conduction abnormalities or structural heart disease, haemophilia A or B, porphyria, increased triglycerides. Renal and severe hepatic impairment (Child Pugh Grade C) w/o decompensation. Childn. Pregnancy.
Adverse Reactions
GI effects (e.g. abdominal pain, nausea, vomiting, diarrhoea, anorexia),
asthenia, taste disorder, headache, numbness or tingling around the mouth or
extremities, anxiety, insomnia, fever, dizziness, malaise, hyperaesthesia,
pharyngitis, rash, pruritus, sweating, vasodilatation, wt loss, allergic
reactions (e.g. urticaria, bronchospasm, angioedema, mild skin eruptions);
immune reconstitution syndrome, lipodystrophy, osteonecrosis, metabolic abnormalities
(e.g. hypertriglyceridaemia, hypercholesterolaemia, insulin resistance,
hyperglycaemia, hyperlactataemia). Reduced levels of Hb, K, free and
total thyroxine; increased eosinophil, liver enzymes, amylase and uric acid;
reduced or increased WBC and neutrophil counts. Potentially Fatal: Pancreatitis, hepatic dysfunction, Stevens-Johnson syndrome. Rarely, anaphylaxis.
Symptoms: Paraesthesia, renal failure w/ eosinophilia. Management: Supportive treatment. Perform gastric lavage and administer activated charcoal.
Drug Interactions
Increases plasma concentrations of budesonide, fluticasone, rivaroxaban. Increased risk of PR interval prolongation w/ (e.g. digoxin, Ca channel blockers, β-blockers, atazanavir). Reduces plasma concentration of raltegravir. Potentially Fatal: Risk of severe hypotension w/ α1-adrenoreceptor antagonist (alfuzosin). Increased risk of serious resp depression or haematologic abnormalities w/ analgesics (pethidine, piroxicam, dextropropoxyphene). Increased risk of cardiac arrhythmias w/ antiarrhythmics (encainide, amiodarone, bepridil, flecainide, quinidine, propafenone), antihistamines (astemizole and terfenadine) and cisapride. Increases plasma concentrations of antibacterial (fusidic acid), rifabutin (ritonavir dose of 600 mg bid), PDE5 inhibitors [avanafil, sildenafil (when used for the treatment of pulmonary arterial HTN), vardenafil]. Increased risk of haematological abnormalities w/ clozapine and pimozide; risk of coma w/ quetiapine). Risk of extreme sedation and resp depression w/ sedatives/hypnotics (clorazepate, diazepam, estazolam, flurazepam, triazolam, oral midazolam). Increases plasma concentrations of ergot derivatives (ergotamine, dihydroergotamine, ergonovine, methylergonovine) leading to acute ergot toxicity including vasospasm and ischaemia. Increased risk of myopathy (including rhabdomyolysis) w/ statins (lovastatin, simvastatin). Significantly reduces plasma concentration which may lead to loss of antifungal response to voriconazole (ritonavir dose ≥400 mg bid).
Food Interaction
Increased absorption w/ food. Reduced concentration w/ St John’s wort.
Action
Description: Ritonavir is a selective, competitive and reversible HIV protease inhibitor that interferes w/ the formation of essential proteins and enzymes. It blocks virus maturation and causes non-functional, immature and non-infectious virions formation. Pharmacokinetics: Absorption: Well absorbed from the GI tract. Increased absorption w/ food. Time to peak plasma concentration: Approx 2-4 hr. Distribution: Enters CNS (minimal amount). Volume of distribution: 0.16-0.66 L/kg. Plasma protein binding: Approx 98%. Metabolism: Extensively metabolised hepatically mainly by CYP3A4 and to a lesser extent by CYP2D6 isoenzymes. Excretion: Via faeces (approx 86%, both as unchanged drug and metabolites); urine (approx 11%, w/ 3.5% as unchanged drug). Elimination half-life: 3-5 hr.
Chemical Structure
Ritonavir Source: National Center for Biotechnology Information. PubChem Database. Ritonavir, CID=392622, https://pubchem.ncbi.nlm.nih.gov/compound/Ritonavir (accessed on Jan. 22, 2020)
Storage
Tab/soln: Store between 20-25°C. Cap: Store between 2-8°C.
J05AE03 - ritonavir ; Belongs to the class of protease inhibitors. Used in the systemic treatment of viral infections.
References
Anon. Ritonavir. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 12/02/2016 .Buckingham R (ed). Ritonavir. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 12/02/2016 .Joint Formulary Committee. Ritonavir. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 12/02/2016 .McEvoy GK, Snow EK, Miller J et al (eds). Ritonavir. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 12/02/2016 .Norvir Capsules. U.S. FDA. https://www.fda.gov/. Accessed 12/02/2016.Norvir Tablet, Film Coated and Solution (AbbVie Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 12/02/2016 .
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