Sustiva (Efavirenz) — Patient-Friendly Guide (United Kingdom)

Sustiva is a medicine used to treat HIV (human immunodeficiency virus). The active ingredient is efavirenz. This page explains how Sustiva works, how it is used, common timing and food considerations, important safety information, and practical tips to help you get the best from your treatment.

Basic product information

What is HIV and what does Sustiva do?

HIV attacks the immune system. Over time, untreated HIV can lead to serious illness. Combination antiretroviral therapy (ART) helps control HIV by reducing the amount of virus in the body to undetectable or very low levels, allowing the immune system to recover.

Mechanism of action (how Sustiva works)

Efavirenz is an NNRTI. HIV uses an enzyme called reverse transcriptase to convert its genetic material into DNA that can integrate into human cells. Efavirenz binds to reverse transcriptase and blocks its action, preventing HIV from making copies of itself.

Pharmacokinetics (how the body handles efavirenz)

Understanding how a medicine moves through the body can help you take it correctly. Efavirenz has some features that influence timing and food advice.

• Absorption: Efavirenz is absorbed after oral dosing. Food can affect how much efavirenz reaches your bloodstream; high-fat meals may increase levels.
• Distribution: It distributes into body tissues and can reach sites where HIV replicates.
• Metabolism: Efavirenz is metabolised mainly in the liver (primarily by CYP enzymes). This is why drug interactions matter.
• Elimination: Efavirenz is cleared relatively slowly. This contributes to a long half-life, supporting once-daily dosing for many people.
• Steady state: It may take several days to reach consistent blood levels. The medicine should still be taken daily as directed to maintain viral suppression.

Typical use in HIV treatment

Sustiva (efavirenz) is used as part of combination antiretroviral therapy. Using only one HIV medicine is usually not enough and can lead to resistance. Your regimen may also include other antiretroviral medicines from different classes.

Indications

Efavirenz is indicated for the treatment of HIV-1 infection in adults and certain paediatric populations depending on local guidance, formulation, and eligibility. It should be used with other antiretroviral medicines in line with current clinical practice.

How and when to take Sustiva

Many people tolerate efavirenz best when it is taken at night. This is because some side effects (such as dizziness or vivid dreams) are commonly noticed during the early period of treatment and may be easier to manage with bedtime dosing.

Timing guidance

• Once daily: Take your dose around the same time each day.
• Night-time dosing is often recommended: If you experience nervous system side effects, taking it in the evening or before bed may help.
• If you miss a dose: Take it as soon as you remember unless it is close to the time for your next dose. Do not take double the dose. Follow the advice given by your healthcare team.
• Consistent daily routine: A stable schedule helps maintain medicine levels to suppress HIV.

Dosing (overview)

Dosing varies by age, weight, and individual clinical factors. In practice, efavirenz is often prescribed as a fixed dose once daily for many adults, but your regimen should match your specialist’s plan. The prescriber (or treatment team) will calculate the correct dose for you.

Important: Do not change your dose or stop treatment without medical advice. Stopping or skipping doses can increase the risk of viral rebound and resistance.

Food interactions (what to eat and what to avoid)

Food can influence efavirenz absorption. The safest approach for many people is to follow the guidance provided with your medicine.

General food advice

• Take as directed regarding meals: If your regimen instructions advise taking on an empty stomach or with specific meal timing, follow them carefully.
• High-fat meals may raise levels: Higher efavirenz blood concentrations may increase the likelihood of nervous system side effects.
• Be consistent: Try not to make sudden major changes in meal size around your dose.

If you have questions about how to take Sustiva with your normal eating pattern (for example, shift work, late evenings, or irregular meal times), speak to your HIV clinic or pharmacist.

Alcohol and medicine interactions

Efavirenz can affect the nervous system in some people. Alcohol may worsen dizziness, drowsiness, impaired concentration, and mood changes.

Alcohol

• Avoid binge drinking: It increases the risk of severe impairment of judgement, falls, and dangerous interactions.
• Watch for increased side effects: If you feel more dizzy or unsteady than usual, reduce or avoid alcohol and seek advice.
• Driving and machinery: If efavirenz makes you feel drowsy or affects attention, avoid driving until you know how you personally respond.

Interactions with other medicines (high importance)

Efavirenz is metabolised through liver pathways (CYP enzymes). Some medicines can either reduce efavirenz levels (leading to poorer HIV control) or increase its levels (increasing side effect risk).

Always tell a healthcare professional about all medicines you take, including over-the-counter products and herbal remedies. Particular attention is needed with:

• Antimycobacterial medicines: Interactions may affect efavirenz effectiveness.
• Anticonvulsants: Some seizure medicines can change efavirenz levels.
• Antifungal and antibiotic medicines: Certain agents can increase or decrease levels.
• St John’s wort (Hypericum perforatum): Typically reduces drug levels and can cause treatment failure.
• Hormonal contraceptives: Interactions are possible; guidance on contraception should be individualised.
• Medicines affecting the central nervous system: Combining with sedatives may increase drowsiness.
• Anticoagulants and heart rhythm medicines: Monitoring may be needed depending on the regimen.

If you are unsure whether a medicine is compatible, ask your pharmacist. A quick check can prevent serious problems.

Safety profile and side effects

Like all medicines, Sustiva can cause side effects. Not everyone gets them. Many early effects improve after the first few weeks as the body adjusts.

Common side effects

• Dizziness and feeling light-headed
• Headache
• Nausea or stomach discomfort
• Sleep disturbances, including vivid dreams
• Fatigue
• Rash (skin changes can occur)

Important warnings (seek urgent advice)

• Severe skin reactions: If you develop a widespread rash, blistering, mouth sores, or skin peeling, seek urgent medical attention.
• Mental health changes: Tell a healthcare professional promptly if you experience severe depression, suicidal thoughts, severe anxiety, confusion, or unusual behaviour.
• Signs of liver problems: Contact medical services if you have persistent nausea/vomiting, yellowing of the eyes/skin, dark urine, severe tiredness, or pain in the right upper abdomen.
• Neurological symptoms: Severe drowsiness, fainting, seizures, or marked worsening of dizziness should be assessed promptly.

Safety considerations for specific groups

• Pregnancy and family planning: Efavirenz has specific considerations in pregnancy. If you could become pregnant, you should discuss contraception and pregnancy plans with your HIV clinic.
• Children and adolescents: Dosing may differ and monitoring is important.
• Liver disease: People with liver problems may need closer monitoring or may be advised against certain medicines due to interaction risk.
• Alcohol use: As above, alcohol can worsen nervous system side effects.

Practical use tips (to make treatment easier)

• Take it at night: If permitted by your instructions, night-time dosing can reduce the impact of dizziness or sleep-related effects.
• Plan for the first weeks: Some symptoms are more common at the start. If symptoms are mild, they often improve, but persistent or severe effects should be reported.
• Build a routine: Link your dose to a consistent bedtime habit (e.g., brushing teeth, preparing for sleep) to reduce missed doses.
• Check interactions early: Before starting any new medicine, including antibiotics, antifungals, migraine treatments, herbal remedies, or supplements, ask for an interaction check.
• Keep follow-up appointments: Routine blood tests and viral load monitoring help confirm that treatment is working and that safety remains appropriate.
• Protect your mood and mental wellbeing: If you notice mood changes or anxiety, seek support early. Getting help early makes a difference.

Alternative options (if efavirenz is not suitable)

Treatment decisions depend on your medical history, previous medicines, viral resistance patterns, side effect profile, drug interactions, and pregnancy considerations. In UK clinical practice, other antiretroviral options may be used instead of efavirenz when appropriate.

Possible alternatives within HIV therapy may include:

• Other NNRTIs (depending on suitability and resistance)
• Integrase strand transfer inhibitors (INSTIs) (commonly used due to tolerability for many patients)
• Protease inhibitors (often boosted in some regimens)
• NRTI backbone combinations paired with a different third agent

Only your HIV specialist can recommend the best combination for you. If you are experiencing side effects or have interaction concerns, discuss switching options promptly.

Market and legal context for the United Kingdom

In the UK, HIV medicines are regulated and supplied within established healthcare pathways. Sustiva (efavirenz) is an established antiretroviral medicine and is used within national and clinic-level treatment strategies. Availability and prescribing practices can vary depending on local formularies, patient suitability, and ongoing guideline updates.

Antiretroviral therapy is typically initiated and monitored by specialist services, and ongoing care includes: viral load testing, safety monitoring, and review of drug interactions.

Recent guidance (what many UK services consider)

UK HIV care typically follows updated guidance from recognised expert bodies and national healthcare policies. Guidance can evolve based on new clinical evidence, resistance considerations, and tolerability improvements.

In recent years, many patients have been treated with integrase-based regimens due to favourable tolerability profiles, but efavirenz may still be used in selected situations where it is suitable and effective. Your clinic may also consider factors such as:

• previous HIV treatment history and resistance testing
• potential drug–drug interactions
• nervous system and mental health tolerability
• pregnancy considerations and contraception requirements
• practical dosing preference and adherence support

Delivery and availability (UK)

Availability can differ by strength, formulation, and supply chain conditions. When ordering from a pharmacy website, you may see:

• In-stock items with standard delivery times
• Backorder or special-order items where dispatch may take longer
• Packaging and patient information leaflet included with the medicine

Delivery times and options vary by supplier and location within the UK. If you need the medicine urgently, check the estimated dispatch and delivery windows shown at checkout, or contact customer support.

FAQ

1) What is Sustiva used for?

Sustiva (efavirenz) is used as part of combination therapy to treat HIV-1. It works by blocking reverse transcriptase, helping reduce HIV levels in the body.

2) How long does it take to work?

Many people see improvements in viral load within weeks, but the exact timeline varies. Your HIV clinic will monitor progress through regular blood tests.

3) Why do people take efavirenz at night?

Efavirenz can cause dizziness, vivid dreams, and sleep disturbances in some people. Night-time dosing may reduce how disruptive these effects feel during the day.

4) Can I take Sustiva with food?

Food can change how much efavirenz is absorbed. Follow the meal advice provided with your medicine or by your healthcare team. If you have been told to take it on an empty stomach or with specific meal timing, it’s important to be consistent.

5) Is it safe to drink alcohol?

Alcohol may increase dizziness and drowsiness and can worsen mood or concentration problems. Avoid binge drinking. If you notice stronger side effects when combining alcohol and efavirenz, reduce or avoid alcohol and seek advice.

6) What medicines should I be especially careful with?

Many medicines can interact with efavirenz through liver enzyme pathways. This includes certain antibiotics and antifungals, seizure medicines, herbal products such as St John’s wort, and some medicines that affect mood or alertness. Always check with a pharmacist before starting anything new.

7) What should I do if I miss a dose?

Take it as soon as you remember unless your next dose is close. Do not take a double dose. If you’re unsure, ask your clinic or pharmacist for advice tailored to your schedule.

8) What side effects are common?

Common side effects include dizziness, headache, nausea, sleep disturbances/vivid dreams, fatigue, and sometimes rash. Many early effects improve with time, but severe or persistent symptoms should be discussed promptly.

9) When should I get urgent help?

Seek urgent medical advice for severe skin reactions (blistering or peeling), signs of liver problems (yellowing skin/eyes, dark urine), severe mood changes or suicidal thoughts, and severe neurological symptoms such as fainting or seizures.

10) Can I stop Sustiva if my HIV is controlled?

Do not stop antiretroviral medicines without medical advice. Stopping treatment can cause viral rebound and increase the risk of resistance.

11) Are there alternatives to Sustiva?

Yes. Depending on your situation, an HIV specialist may recommend different antiretroviral medicines or a different combination. If efavirenz is not suitable due to side effects or interactions, discuss options early.

12) Does Sustiva affect driving?

It can. If efavirenz makes you feel dizzy, drowsy, or affects concentration, avoid driving and operating machinery until you know how you respond and your symptoms are controlled.

Important note

This information is intended to help you understand Sustiva (efavirenz) and how it is commonly used. Your individual regimen may differ based on your health profile and treatment history. Always follow the specific advice given by your HIV clinic and pharmacist, and read the patient information leaflet supplied with your medicine.