Formulary
Fosamprenavir: Indications, Dosing, Side Effects and Interactions
Fosamprenavir is a pro-drug of amprenavir.
MedNext Academy | 3 min read
Fosamprenavir: Indications, Dosing, Side Effects and Interactions
Fosamprenavir is a pro-drug of amprenavir.
Drug action
Fosamprenavir is a pro-drug of amprenavir.
Indications and dose
**HIV infection in combination with other antiretroviral drugs-with low-dose ritonavir**
- **Adult** (By Mouth): 700 mg twice daily.
**HIV infection in combination with other antiretroviral drugs-with low-dose ritonavir for fosamprenavir**
- **Child 6-17 years (body-weight 25-39 kg)** (By mouth): 18 mg/kg twice daily (max. per dose 700 mg).
- **Child 6-17 years (body-weight 40 kg and above)** (By mouth): 700 mg twice daily.
Cautions
For all protease inhibitors Haemophilia (increased risk of bleeding)
Contraindications
For all protease inhibitors Acute porphyrias
Side effects
For all protease inhibitors Common or very common Angioedema; anxiety; appetite abnormal; arthralgia; asthenia; diabetes mellitus; diarrhoea; dizziness; dyslipidaemia; fever; gastrointestinal discomfort; gastrointestinal disorders; headache; hepatic disorders; hypersensitivity; hypertension; myalgia; nausea; oral ulceration; pancreatitis; peripheral neuropathy; seizure; skin reactions; sleep disorders; syncope; taste altered; urinary frequency increased; vomiting Uncommon Alopecia; dry mouth; immune reconstitution inflammatory syndrome; myocardial infarction; osteonecrosis; weight increased Rare or very rare Stevens-Johnson syndrome Side-effects For fosamprenavir Common or very common Oral paraesthesia Side-effects, further information Rash may occur, usually in the second week of therapy; discontinue permanently if severe rash with systemic or allergic symptoms or, mucosal involvement; if rash mild or moderate, may continue without interruption-usually resolves and may respond to antihistamines.
Interactions
**Severe interactions:**
- Fosamprenavir/ ritonavir (700/100 mg BID) (Lopinavir/ritonavir 400/100 mg BID) or Fosamprenavir (1400 mg BID) (Lopinavir/ritonavir 533/133 mg BID) Fosamprenavir: Amprenavir concentrations are...
- Possible toxicity with phenytoin on stopping primidone); stiripentol, tiagabine, valproic acid, zonisamide.
**Other interactions (17):**
- Amprenavir, fosamprenavir Not studied.
- Fosamprenavir 1400 mg BID Amprenavir AUC 0.67 (0.55-0.80) Amprenavir C min 0.65 (0.49-0.85) Amprenavir C max 0.75 (0.63-0.89) Nevirapine AUC 1.29 (1.19-1.40) Nevirapine C min 1.34...
- Fosamprenavir/ ritonavir 700/ 100 mg BID Amprenavir AUC 0.89 (0.77-1.03) Amprenavir C min 0.81 (0.69-0.96) Amprenavir C max 0.97 (0.85-1.10) Nevirapine AUC 1.14 (1.05-1.24) Nevirapine C min...
- Antivirals: ritonavir-boosted darunavir, ritonavir-boosted fosamprenavir, indinavir (see also under 'Drugs that may have their plasma concentrations increased by itraconazole'), ritonavir (see also...
- Co-administration of increased doses of fosamprenavir (1400 mg BID) with Kaletra (533/133 mg BID) to protease inhibitor-experienced patients resulted in a higher incidence of gastrointestinal...
- Monitor for fesoterodine or solifenacin adverse reactions, dose reduction of fesoterodine or solifenacin may be necessary.
Pregnancy
Toxicity in animal studies; manufacturer advises use only if potential benefit outweighs risk.
Hepatic impairment
For all protease inhibitors In general, manufacturers advise use with caution in patients with chronic hepatitis B or C (increased risk of hepatic side-effects). Hepatic impairment For fosamprenavir Manufacturer advises caution. Dose adjustments Manufacturer advises dose reduction to 450 mg twice daily in moderate impairment and 300 mg twice daily in severe impairment.
Medicinal forms
Medicinal forms No licensed medicines listed.
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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