If you miss a dose

If you miss a dose, take it as soon as you remember unless it is nearly time for the next dose. Avoid taking a double dose. If you are unsure, ask your pharmacist.

Food interactions and what you should eat

Food can affect efavirenz exposure. In particular, high-fat meals may increase efavirenz levels in the blood, which may increase the risk of side effects (for example, dizziness or central nervous system symptoms).

Practical advice:

• Prefer: taking efavirenz with a light meal or when food is consistent with your clinician’s advice.
• Avoid: very fatty meals close to your dose if you notice side effects after eating.
• Do not make major meal timing changes suddenly without discussing with your pharmacist or clinician.

If you experience troublesome side effects, it can be useful to note what and when you ate in relation to your dose.

Alcohol and medicine interactions

Alcohol

Drinking alcohol may worsen some efavirenz-related side effects such as dizziness, drowsiness, impaired concentration, and mood changes. For many people, it is safest to limit alcohol and avoid heavy drinking, especially when starting treatment or changing dose.

Other medicines (important interactions)

Efavirenz can interact with many medicines due to its metabolism in the liver and its effect on certain enzymes and transport pathways. Some interactions can reduce effectiveness of HIV treatment or increase side-effect risk.

Always check:

• Antifungal medicines (e.g., certain azoles)
• Antibiotics or antivirals
• Medicines for seizures (antiepileptics)
• Rifampicin/rifabutin (tuberculosis medicines)
• Hormonal contraceptives (see below)
• Psychiatric medications (antidepressants, antipsychotics, sleep aids)
• St John’s wort (a common herbal product)—generally should be avoided
• Oral anticoagulants (blood thinners) and other medicines with narrow safety margins

Tell your pharmacist about all medicines you take, including over-the-counter products, vitamins, and herbal supplements.

Indications (what it is used for)

Sustiva (efavirenz) is indicated for the treatment of HIV-1 infection as part of combination antiretroviral therapy.

Efavirenz is generally chosen when it is suitable based on:

• HIV resistance profile
• Medication interaction risk
• Comorbidities (including mental health and liver function)
• Contraception and pregnancy considerations

Dosing: typical adult regimen

Efavirenz dosing may differ by tablet strength and patient factors. In many adult regimens, efavirenz is taken once daily. The most important rule is: use the exact dose your clinician has prescribed for you.

Common dosing approach (adults)

• Once daily dosing
• Bedtime timing is often used to help reduce central nervous system symptoms

Children and adolescents

Dosing in paediatric patients may be weight-based and may use different formulations. Follow the dosing plan provided by the child’s HIV team.

Liver or kidney impairment

Efavirenz is mainly metabolised by the liver. If you have liver disease, your clinician may need closer monitoring or dose considerations. Kidney impairment usually has less impact, but you should still inform your healthcare team about all health conditions.

Safety profile: what to watch for

Like all medicines, efavirenz can cause side effects. Many people experience mild symptoms early on, and these may improve as your body adjusts. However, some side effects require urgent medical attention.

Common side effects

• Dizziness
• Sleep-related symptoms (e.g., vivid dreams)
• Headache
• Nausea
• Fatigue
• Rash (often appears in early weeks)

Neuropsychiatric effects (seek advice promptly)

Efavirenz may cause mood and mental health changes in some people, including:

• Confusion
• Anxiety
• Depression
• Unusual thoughts or behaviour
• Severe agitation
• Rarely, suicidal thoughts

If you develop severe or worsening symptoms, contact your healthcare team promptly. Do not stop treatment without professional advice—interruption can lead to loss of viral suppression.

Skin reactions

Mild rash can occur. Severe skin reactions (rare) may be serious. Seek urgent medical help if you have:

• Blistering or peeling skin
• Rash with fever or feeling very unwell
• Sores in the mouth or eyes

Liver effects

Efavirenz can affect liver enzymes. Your clinician may perform blood tests to monitor liver function, especially if you have existing liver disease or hepatitis co-infection.

Long-term considerations

• Lipid changes: some people see changes in cholesterol or triglycerides.
• Bone and metabolic health: risk depends on the overall regimen and your health factors.
• Adherence impact: missed doses may increase viral replication and risk of resistance.

Practical use tips for better tolerability

• Take at bedtime (often helps): if dizziness or vivid dreams occur, bedtime dosing can reduce disruption.
• Keep a simple routine: taking it at the same time daily supports adherence.
• Manage early side effects: symptoms like dizziness may improve over the first few weeks for some people.
• Light meals can help: try to avoid heavy, high-fat meals near dosing if you notice a link to side effects.
• Alcohol awareness: reduce alcohol especially when first starting or if you feel “cloudy” or unsteady.
• Know red flags: get urgent help for severe skin reactions, severe mood changes, or signs of liver problems.
• Don’t skip doses: consistent daily dosing protects the effectiveness of your regimen.

Alternative options (other antiretrovirals)

Alternative treatments depend on your viral load, resistance testing, prior regimens, co-medications, comorbidities, and pregnancy plans. Efavirenz is one option within the NNRTI class. Your clinician may consider alternatives such as:

• Other NNRTIs: e.g., rilpivirine or doravirine (suitability varies by regimen and resistance)
• Integrase inhibitors: e.g., dolutegravir or bictegravir (often used in modern first-line regimens)
• Protease inhibitors: e.g., darunavir (sometimes preferred for certain resistance patterns)
• NRTI backbone options: typically combined with other agents such as tenofovir and emtricitabine/lamivudine

If you are considering switching due to side effects or interactions, discuss timing and overlap strategies with your HIV team. Switching should be planned to maintain viral suppression.

UK market and legal context (high-level)

In the United Kingdom, antiretroviral medicines are regulated and supplied through licensed channels. For online pharmacy services, availability and dispatch generally depend on:

• Regulatory approval and marketing authorisation for the UK
• Supply chain status and stock levels
• Clinical suitability and patient eligibility checks
• Cold chain or storage needs (if applicable—efavirenz tablets generally do not require refrigeration)

Medicines may be supplied via NHS services, private HIV clinics, or pharmacies that support ongoing treatment. Policies can change, and local availability may vary over time.

Recent guidance and regimen considerations (UK clinical practice)

HIV treatment recommendations in the UK are shaped by national guidance and international evidence. Clinicians commonly aim for regimens that:

• Achieve rapid and durable viral suppression
• Have a strong resistance profile for the individual patient
• Minimise serious side effects and drug interactions
• Support adherence (e.g., once-daily options where suitable)
• Account for pregnancy and contraception needs

Efavirenz may still be used when appropriate, but it may be avoided in some situations (for example, where neuropsychiatric side effects are a concern, when safer alternatives fit the patient’s circumstances, or where drug interactions are difficult to manage).

Your HIV specialist will consider current recommendations when deciding what regimen is best for you.

Delivery and availability in the UK

Online pharmacy availability for Sustiva may vary by:

• Tablet strength and formulation
• Current manufacturer and wholesale stock
• Dispatch timeframes used by the pharmacy
• Standard vs. expedited delivery (where offered)

When ordering, check:

• Estimated delivery dates shown at checkout
• Packaging and storage instructions
• Return policy and contact details in case of supply issues

In case a product is temporarily unavailable, some pharmacies may contact you with alternatives or delivery updates.

Storage information

• Keep tablets in the original packaging.
• Store at room temperature and away from excess heat or moisture.
• Keep out of sight and reach of children.
• Check the leaflet for any specific storage instructions provided with your pack.

FAQ – Sustiva (Efavirenz)

1. What is Sustiva used for?

Sustiva (efavirenz) is used as part of combination therapy to treat HIV-1 infection. It works by blocking HIV reverse transcriptase.

2. How soon will it start working?

Many people achieve a drop in viral load quickly after starting effective combination therapy. The exact timeline varies. Your clinician will monitor response with blood tests, typically including viral load measurements and blood counts/chemistry where appropriate.

3. Why do I feel dizzy or have vivid dreams?

Central nervous system effects such as dizziness and vivid dreams can occur, particularly in the early weeks. Taking the dose at bedtime may reduce disruption. If symptoms are severe or worsening, contact your healthcare team.

4. Can I take Sustiva with food?

Food can influence efavirenz levels. If you notice side effects after certain meals, try to keep meals consistent and discuss with your pharmacist. Avoid very high-fat meals near dosing if advised for your situation.

5. What medicines should I avoid with efavirenz?

Efavirenz can interact with many medicines. Particularly important examples include some anticonvulsants, certain antibiotics/antifungals, tuberculosis medicines, herbal products like St John’s wort, and some psychiatric or hormonal treatments. Always provide a full list of your medicines to your pharmacist for interaction checking.

6. Is alcohol safe while taking Sustiva?

Alcohol may worsen dizziness, drowsiness, mood changes, and impaired concentration. Limiting or avoiding alcohol is recommended, especially when starting treatment or if you notice side effects.

7. What if I become pregnant or want to conceive?

Pregnancy planning is very important with efavirenz and other antiretrovirals. Discuss contraception and pregnancy intentions with your HIV clinic. Your clinician can guide the safest approach for your situation.

8. What should I do if I miss a dose?

Take it as soon as you remember unless it is close to the time of your next dose. Do not take double doses. If you are unsure, contact your pharmacist or HIV clinic for advice.

9. Are there any warning signs that mean I should seek urgent help?

Yes. Seek urgent medical help for severe rash, blistering/peeling skin, rash with fever, severe mood changes (including thoughts of self-harm), or signs of liver problems such as yellowing of the eyes/skin, severe abdominal pain, or dark urine.

10. What are typical side effects vs serious side effects?

Common side effects include dizziness, headache, nausea, and vivid dreams. Serious side effects are less common but can include severe skin reactions, significant psychiatric symptoms, and liver problems. If side effects are severe, persistent, or concerning, seek medical advice promptly.

Disclaimer: This information is for general educational purposes and does not replace medical advice from your clinician or pharmacist. Individual factors such as other medicines, liver function, mental health history, and test results can change what is safest for you.