Efavirenz (EFV) — Patient Information
Efavirenz is an antiretroviral medicine used in the treatment of HIV (human immunodeficiency virus). It belongs to a class of medicines called NNRTIs (non-nucleoside reverse transcriptase inhibitors). This page explains how Efavirenz works, how it is used, common safety considerations, interactions, and practical tips to help you use it as safely as possible.
In the UK, Efavirenz may be used as part of combination HIV therapy, depending on your treatment plan and national/local guidance. Always follow the advice of your healthcare team.
Basic product information
| Item | Information |
|---|---|
| Active ingredient | Efavirenz |
| Medicine type | Antiretroviral (NNRTI) |
| Common formulations | Tablets (strengths vary by product) |
| How it is usually taken | Oral, once daily (often at bedtime) |
| Key use | HIV treatment in combination with other antiretrovirals |
Mechanism of action
HIV needs an enzyme called reverse transcriptase to copy itself inside your body. Efavirenz works by binding to reverse transcriptase and blocking its activity. This prevents HIV from making copies of itself, which helps reduce the amount of virus in the blood and improves immune function over time.
Efavirenz is effective only as part of a combination regimen. Using it alone can lead to rapid viral resistance.
Pharmacokinetics (how the body handles it)
Pharmacokinetics explains how the medicine is absorbed, distributed, metabolised, and eliminated. Efavirenz is known for a relatively long duration of action due to its metabolism.
Absorption
- Efavirenz is absorbed from the gut after taking a dose.
- Food can significantly affect levels of efavirenz in the bloodstream (see “Food interactions” below).
Distribution
- Efavirenz distributes into body tissues, including the central nervous system (which is relevant to possible neurological side effects).
Metabolism
- Efavirenz is metabolised primarily in the liver, largely through the CYP450 enzyme system (especially CYP2B6).
- This is why interactions with other medicines—particularly those affecting CYP enzymes—may be important.
Elimination
- Efavirenz has a long elimination half-life, which supports once-daily dosing.
- It is cleared mainly through metabolism, with metabolites excreted via urine and faeces.
Typical use in HIV treatment
Efavirenz is used for HIV infection as part of an effective combination antiretroviral regimen. The exact combination depends on factors such as:
- your previous HIV treatment history
- your viral load and CD4 count
- drug resistance testing where appropriate
- co-infections (for example hepatitis B or C)
- other medicines you take (to reduce interactions)
- pregnancy status and other individual considerations
How and when to take Efavirenz
Many people are advised to take Efavirenz once daily and often at bedtime. This can help reduce common early side effects such as dizziness or vivid dreams.
Timing tips
- Try to take your dose at the same time each day.
- If you experience early sleep-related or nervous system effects, bedtime dosing may help.
- Avoid missing doses—regular use helps keep HIV under control.
If you forget a dose
If you miss a dose, follow the guidance provided with your medicine. In general, taking it as soon as you remember on the same day is often recommended, but the safest approach depends on timing and your situation. If you are unsure, ask your pharmacist or healthcare team.
Food interactions
Food can increase efavirenz exposure, which may raise the risk of side effects for some people. For this reason, many regimens recommend taking Efavirenz with a particular meal pattern.
A common practical approach is:
- Take Efavirenz on an empty stomach or with a light meal, depending on local guidance and your product instructions.
- Avoid large, high-fat meals if your medicine advice says this.
Because product instructions can differ by formulation, always check the leaflet supplied with your specific pack. If you have questions, ask your pharmacist.
Alcohol and medicine interactions
Alcohol
Efavirenz can cause dizziness, sleep disturbances, or impaired concentration in some people—especially early on. Alcohol may worsen these effects. For safer use:
- Limit alcohol, particularly during the first weeks of treatment.
- Avoid driving or operating machinery if you feel drowsy, dizzy, or “not yourself.”
Interactions with other medicines (key examples)
Efavirenz interacts with many medicines because it can affect and be affected by liver enzymes. Tell your healthcare team and pharmacist about all medicines you take, including:
- prescription medicines
- over-the-counter products
- herbal remedies
- vitamins and supplements
The most clinically relevant interactions often involve medicines that: reduce efavirenz levels (leading to treatment failure) or increase efavirenz levels (leading to more side effects).
Common interaction themes
- Medicines that induce CYP enzymes (for example some anticonvulsants and herbal products like St John’s wort) may lower efavirenz levels.
- Medicines that inhibit CYP enzymes may raise efavirenz levels.
- Some medicines may have combined effects on the nervous system or the liver.
Herbal products: St John’s wort
Do not use St John’s wort while taking Efavirenz unless your clinician specifically instructs it. It can reduce blood levels of efavirenz and compromise HIV control.
Opioids, sleep medicines, and sedatives
Efavirenz may add to sleepiness or dizziness from sedatives, some pain medicines, and other treatments affecting the central nervous system. Use caution and seek advice if you need these medicines.
If you want, share a list of your current medicines (including non-prescription and herbal products) and a pharmacist can help check for potential interactions.
Indications: when Efavirenz is used
In the UK, Efavirenz is indicated as part of combination HIV therapy for adults and selected patient groups. Specific eligibility and the best regimen choice depend on:
- treatment history (new start vs switching)
- resistance profile
- co-morbidities and other medicines
- pregnancy considerations and risk assessment
Your clinician may choose Efavirenz when appropriate or may prefer other antiretrovirals depending on individual factors and current guidance.
Dosing (general guidance)
Efavirenz dosing depends on your regimen and product strength. The most common adult dosing is:
- Typically once daily, often at bedtime
Some patients may use paediatric or weight-based dosing depending on local treatment protocols. Always use the exact instructions provided with your specific product and by your healthcare team.
Missed doses and dose adjustments
- Do not change your dose unless a clinician advises it.
- If you have liver problems, your clinician may monitor you more closely or consider a different regimen.
- If you start or stop other medicines, dose adjustments or extra monitoring may be required due to interactions.
If you experience troubling side effects (for example persistent dizziness, mood changes, or rash), contact your healthcare team promptly—especially if symptoms are severe or rapidly worsening.
Safety profile
Like all medicines, Efavirenz can cause side effects. Not everyone gets them, and many early effects improve with time. It’s important to know what to watch for.
Common side effects
- Dizziness
- Sleep disturbance (including vivid dreams)
- Headache
- Nausea
- Fatigue
These are often most noticeable during the first few weeks. Taking the medicine at bedtime and avoiding alcohol may help.
Skin reactions
A rash can occur. Some rashes are mild, but certain skin reactions can be serious. Seek urgent medical attention if you develop:
- severe blistering or peeling skin
- ulcers in the mouth or around the eyes
- fever with a rash
- widespread rash with feeling very unwell
Psychiatric and nervous system effects
Efavirenz may affect mood or cause unusual thoughts in some people. Contact your healthcare team urgently if you experience:
- severe anxiety or agitation
- depression that is new or worsening
- hallucinations, confusion, or severe sleep disruption
- thoughts of self-harm
If you have a history of mental health conditions, tell your clinician—additional monitoring may be needed.
Liver effects
Efavirenz is metabolised in the liver. Liver inflammation or increased liver enzymes can occur. Tell your healthcare team if you notice:
- yellowing of the skin/eyes (jaundice)
- dark urine
- persistent nausea or abdominal pain
- unusual tiredness or itching
Interactions can affect safety
Because efavirenz interacts with many medicines, safety depends not just on efavirenz itself, but on your overall regimen. Always check before starting any new medicine, including herbal products.
Practical use tips for patients
- Use a routine: take it at the same time each day to support adherence.
- Bedtime dosing: if you feel dizzy or notice vivid dreams, this often helps.
- Be careful with alcohol: it may worsen dizziness or sleep disruption.
- Watch for rash early: contact your clinician quickly if a rash appears.
- Keep a medicine list: include prescription, non-prescription, and herbal products.
- Don’t miss combination therapy: Efavirenz works best as part of a complete HIV regimen.
- Attend monitoring appointments: routine blood tests help check viral response and safety.
Alternative options
Efavirenz is one of several antiretroviral options. Depending on your circumstances and current guidance, clinicians may consider:
- Other NNRTIs (for example medicines with different interaction profiles)
- Integrase inhibitors (often used in many modern regimens)
- Protease inhibitor–based regimens
- NRTI backbones paired with an alternative “anchor” medicine
The “best” alternative depends on factors such as co-existing conditions, potential drug interactions, and resistance history. Discuss options with your HIV specialist or clinical pharmacist.
United Kingdom market and legal context (overview)
In the UK, medicines are regulated by the Medicines and Healthcare products Regulatory Agency (MHRA). Efavirenz is an established antiretroviral used in HIV care. Availability and prescribing practices can evolve over time as treatment guidelines and evidence develop.
In routine care, HIV treatment is usually managed through specialist services (including NHS HIV clinics). Medicines supplied through UK pharmacies should be sourced and supplied in line with medicines regulations and quality requirements.
If you are buying through an online pharmacy, ensure the site is legitimate and that medicines are supplied by authorised pharmacy services. This helps protect quality, authenticity, and safe dispensing.
Recent guidance (high-level)
HIV treatment guidance in the UK is regularly updated by clinical bodies and expert groups as new evidence emerges. Current practice often emphasises:
- using effective combination therapy to achieve and maintain viral suppression
- considering individual factors such as co-morbidities, drug interactions, and tolerability
- supporting adherence and monitoring for side effects
- choosing regimens with a favourable benefit–risk balance for each person
Efavirenz may still be used in some circumstances, but clinicians may prefer other options depending on your specific situation—particularly if there are concerns about neurological side effects, interactions, or pregnancy-related considerations.
Delivery and availability in the UK
Availability can vary by formulation, strength, and stock levels. In general, UK online pharmacies may provide:
- standard delivery to UK addresses (timeframes vary)
- tracked delivery options
- discrete packaging
Before ordering, check:
- current stock status (“in stock” vs “pre-order”)
- delivery speed and cut-off times
- returns and replacement policy if your order is incorrect or damaged
- how to contact customer support if you have questions
If you need urgent supply to avoid treatment interruption, contact the pharmacy promptly so they can advise on the fastest available options.
FAQ
1) What is Efavirenz used for?
Efavirenz is used to treat HIV infection as part of a combination antiretroviral regimen. It reduces viral activity by blocking HIV reverse transcriptase.
2) How long does it take to work?
Many people see reductions in viral load within weeks of starting effective therapy. The exact timeline varies. Your clinician will monitor your response using blood tests.
3) Should I take Efavirenz with food?
Food can change efavirenz levels. Follow the instructions provided with your specific product. If your guidance recommends taking it on an empty stomach or with a light meal, try to follow that consistently.
4) Why is bedtime dosing often recommended?
Efavirenz can cause dizziness, vivid dreams, or sleep disturbance—especially early in treatment. Taking it at bedtime may make these effects less noticeable and can support comfort with early therapy.
5) Can I drink alcohol while taking Efavirenz?
Alcohol may increase side effects like dizziness, drowsiness, and sleep disruption. If you choose to drink, do so cautiously—particularly during the first weeks—and avoid activities requiring alertness if you feel affected.
6) What interactions should I be particularly careful about?
Efavirenz can interact with medicines that affect liver enzymes. Avoid starting new medicines (including herbal products) without advice. In particular, do not use St John’s wort. Always share a complete medication list with your pharmacist or clinician.
7) What side effects are most concerning?
Seek urgent medical advice for severe rash, blistering/peeling skin, signs of liver problems (such as jaundice), or severe mental health symptoms (for example hallucinations or thoughts of self-harm). For less severe effects, contact your healthcare team for guidance.
8) What if I miss a dose?
Follow the guidance provided with your medicine. In general, you should not double up without advice. If you are unsure, ask your pharmacist for instructions based on when you missed the dose.
9) Can Efavirenz be switched to another HIV medicine?
Switching may be possible, but it depends on your regimen, viral resistance, and your experience with side effects. Any change should be planned with your HIV specialist or clinical team.
10) Is Efavirenz suitable for everyone?
Suitability depends on your medical history, other medicines, liver function, and other individual factors. Your clinician will consider these before starting or continuing therapy.
Important: This information is intended to help you understand Efavirenz and common considerations. It does not replace personalised medical advice. If you have symptoms you are worried about, or questions about interactions, contact your pharmacist or healthcare team promptly.
