Formulary
Efavirenz: Indications, Dosing, Side Effects and Interactions
Efavirenz clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 4 min read
Efavirenz: Indications, Dosing, Side Effects and Interactions
Efavirenz clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**HIV infection in combination with other antiretroviral drugs**
- **Adult** (By Mouth Using Capsules): 600 mg once daily.
- **Adult** (By Mouth Using Tablets): 600 mg once daily.
**HIV infection in combination with other antiretroviral drugs for efavirenz**
- **Child 3 months-17 years (body-weight 3.5-4 kg)** (By mouth using capsules): 100 mg once daily.
- **Child 3 months-17 years (body-weight 5-7.4 kg)** (By mouth using capsules): 150 mg once daily.
- **Child 3 months-17 years (body-weight 7.5-14 kg)** (By mouth using capsules): 200 mg once daily.
- **Child 3 months-17 years (body-weight 15-19 kg)** (By mouth using capsules): 250 mg once daily.
- **Child 3 months-17 years (body-weight 20-24 kg)** (By mouth using capsules): 300 mg once daily.
- **Child 3 months-17 years (body-weight 25-32.4 kg)** (By mouth using capsules): 350 mg once daily.
- **Child 3 months-17 years (body-weight 32.5-39 kg)** (By mouth using capsules): 400 mg once daily.
- **Child 3 months-17 years (body-weight 40 kg and above)** (By mouth using capsules): 600 mg once daily.
- **Child (body-weight 40 kg and above)** (By mouth using tablets): 600 mg once daily.
Cautions
Acute porphyrias ; elderly; history of psychiatric disorders; history of seizures; risk of QT interval prolongation
Side effects
Common or very common Abdominal pain; anxiety; concentration impaired; depression; diarrhoea; dizziness; drowsiness; dyslipidaemia; fatigue; headache; movement disorders; nausea; skin reactions; sleep disorders; vomiting Uncommon Behaviour abnormal; confusion; flushing; gynaecomastia; hallucination; hepatic disorders; memory loss; mood altered; pancreatitis; psychosis; seizure; Stevens-Johnson syndrome; suicidal behaviours; thinking abnormal; tinnitus; tremor; vertigo; vision blurred Rare or very rare Delusions; photosensitivity reaction Frequency not known Immune reconstitution inflammatory syndrome; osteonecrosis Side-effects, further information Rash Rash, usually in the first 2 weeks, is the most common side-effect; discontinue if severe rash with blistering, desquamation, mucosal involvement or fever; if rash mild or moderate, may continue without interruption-usually resolves within 1 month. CNS effects Administration at bedtime especially in first 2-4 weeks reduces CNS effects. Abnormal hepatic function Manufacturer advises interrupt or discontinue treatment if transaminases more than 5 times the upper limit of normal.
Interactions
**Severe interactions:**
- Fosamprenavir/ritonavir/Efavirenz (700 mg twice daily/100 mg twice daily/600 mg once daily) Fosamprenavir/Nelfinavir/ Efavirenz Fosamprenavir/Saquinavir/ Efavirenz No clinically significant...
- Indinavir/Efavirenz (800 mg q8h/200 mg once daily) Indinavir: AUC : 31% ( 8 to 47) C min : 40% A similar reduction in indinavir exposures was observed when indinavir 1000 mg q8h was given...
- Indinavir/ritonavir/Efavirenz (800 mg twice daily/100 mg twice daily/600 mg once daily) Indinavir: AUC: 25% ( 16 to 32) b C max : 17% ( 6 to 26) b C min : 50% ( 40 to 59) b Efavirenz:...
- Clinically significant interactions are not expected since the NRTIs are metabolised via a different route than efavirenz and would be unlikely to compete for the same metabolic enzymes and...
- Simeprevir/Efavirenz (150 mg once daily/600 mg once daily) Simeprevir: AUC: 71% (67 to 74) C max : 51% (46 to 56) C min : 91% (88 to 92) Efavirenz: AUC: C max : C min : No effect ()...
- Glecaprevir/pibrentasvir glecaprevir pibrentasvir Concomitant administration of glecaprevir/pibrentasvir with efavirenz may significantly decrease plasma concentrations of glecaprevir and...
- Antibiotics Azithromycin/Efavirenz (600 mg single dose/400 mg once daily) No clinically significant pharmacokinetic interaction.
- Antifungals Itraconazole/Efavirenz (200 mg q12h/600 mg once daily) Itraconazole: AUC: 39% ( 21 to 53) C max : 37% ( 20 to 51) C min : 44% ( 27 to 58) (decrease in itraconazole...
**Other interactions (93):**
- Efavirenz is an in vivo inducer of CYP3A4, CYP2B6 and UGT1A1.
- Compounds that are substrates of these enzymes may have decreased plasma concentrations when co- administered with efavirenz.
- In vitro efavirenz is also an inhibitor of CYP3A4.
- Theoretically, efavirenz may therefore initially increase the exposure to CYP3A4 substrates and caution is warranted for CYP3A4 substrates with narrow therapeutic index (see section 4.3).
- Efavirenz may be an inducer of CYP2C19 and CYP2C9; however, inhibition has also been observed in vitro and the net effect of co- administration with substrates of these enzymes is not clear (see...
- Efavirenz exposure may be increased when given with medicinal products (for example, ritonavir) or food (for example, grapefruit juice), which inhibit CYP3A4 or CYP2B6 activity.
Pregnancy
Reports of neural tube defects when used in first trimester.
Hepatic impairment
Greater risk of hepatic side-effects in chronic hepatitis B or C. Manufacturer advises avoid in severe impairment (limited information available).
Renal impairment
Manufacturer advises caution in severe renal failure-no information available.
Medicinal forms
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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