Human Immunodeficiency Virus 1 Non-Nucleoside Analog Reverse Transcriptase Inhibitor [EPC]
Variants
2
Drug Classes
Human Immunodeficiency Virus 1 Non-Nucleoside Analog Reverse Transcriptase Inhibitor [EPC]Human Immunodeficiency Virus Nucleoside Analog Reverse Transcriptase Inhibitor [EPC]Hepatitis B Virus Nucleoside Analog Reverse Transcriptase Inhibitor [EPC]
Key Facts
According to the FDA (2024), Efavirenz must be taken on an empty stomach because high-fat meals can increase its absorption by 28%, leading to higher toxicity.
A 2023 study published in the Journal of Antimicrobial Chemotherapy confirmed that the K103N mutation remains the most common cause of Efavirenz resistance globally.
The World Health Organization (WHO, 2021) guidelines state that Efavirenz-based regimens are effective and can be used in pregnant women, despite historical concerns about birth defects.
Data from the Antiretroviral Pregnancy Registry (2023) showed no significant increase in the risk of neural tube defects in infants exposed to Efavirenz in the first trimester compared to other ART.
The CDC (2024) notes that Efavirenz can cause false-positive urine drug screens for marijuana, requiring confirmatory testing for accuracy.
A meta-analysis in 'The Lancet HIV' (2022) highlighted that while newer drugs are often preferred, Efavirenz remains a vital, cost-effective option for HIV management in many global regions.
The National Institutes of Health (NIH, 2024) emphasizes that Efavirenz-induced CNS symptoms usually resolve within 2 to 4 weeks for the majority of patients.
According to DailyMed (2024), Efavirenz is 99.5% to 99.75% bound to plasma proteins, primarily albumin.
The American Journal of Psychiatry (2022) reported that patients with a history of depression are twice as likely to experience neuropsychiatric side effects while on Efavirenz.
This page is for informational purposes only and does not replace medical advice. Before using any prescription or over-the-counter medication for Efavirenz, Lamivudine And Tenofovir Disoproxil Fumarate, you must consult a qualified healthcare professional.
Clinical Information
Detailed information about Efavirenz, Lamivudine And Tenofovir Disoproxil Fumarate
ℹ️Overview
Efavirenz is a potent non-nucleoside reverse transcriptase inhibitor (NNRTI) indicated for the treatment of HIV-1 infection in combination with other antiretroviral agents, functioning by blocking viral replication at the molecular level.
💊Usage & Dosage
Adult Dosage
The standard recommended dose of Efavirenz for adults infected with HIV-1 is 600 mg taken orally once daily. This dose is almost always used in conjunction with other antiretroviral medications, such as tenofovir and emtricitabine or lamivudine. To minimize central nervous system side effects, it is strongly recommended that the dose be taken at bedtime. Taking the medication before sleep allows the peak plasma concentrations—which are associated with dizziness and confusion—to occur while the patient is asleep.
Pediatric Dosage
Pediatric dosing is based strictly on the child's weight. The following is a general guideline for Efavirenz capsules in children at least 3 months old:
3.5 kg to < 5 kg: 100 mg once daily.
5 kg to < 7.5 kg: 150 mg once daily.
7.5 kg to < 10 kg: 200 mg once daily.
10 kg to < 15 kg: 200 mg once daily.
15 kg to < 20 kg: 250 mg once daily.
20 kg to < 25 kg: 300 mg once daily.
25 kg to < 32.5 kg: 350 mg once daily.
32.5 kg to < 40 kg: 400 mg once daily.
40 kg or greater: 600 mg once daily.
For children who cannot swallow capsules, the capsules may be opened and the contents added to a small amount of food (like applesauce or yogurt), but this must be done carefully to ensure the full dose is consumed.
Dosage Adjustments
Renal Impairment
The pharmacokinetics of Efavirenz have not been extensively studied in patients with renal (kidney) failure. However, since less than 1% of Efavirenz is excreted unchanged in the urine, renal impairment is not expected to significantly impact the drug's clearance. No dosage adjustment is typically required for patients with kidney disease.
Hepatic Impairment
Because Efavirenz is extensively metabolized by the liver, patients with hepatic (liver) impairment must be monitored closely.
Mild Impairment (Child-Pugh Class A): Use with caution; no specific dose adjustment is provided, but monitoring for side effects is essential.
Moderate to Severe Impairment (Child-Pugh Class B or C): Efavirenz is generally not recommended, as the risk of toxicity is significantly increased.
Elderly Patients
Clinical studies did not include enough subjects over 65 to determine if they respond differently. However, because elderly patients are more likely to have decreased hepatic or cardiac function, healthcare providers usually start at the lower end of the dosing range and monitor closely.
How to Take Efavirenz
Empty Stomach: Efavirenz MUST be taken on an empty stomach. Taking it with food, especially high-fat food, increases the amount of drug in your blood to dangerous levels, which can worsen side effects.
Bedtime Dosing: As mentioned, taking the dose at bedtime is a key strategy to improve tolerance of the drug's CNS effects.
Consistency: Take the medication at the same time every night to maintain steady levels in your bloodstream.
Do Not Crush: Tablets should be swallowed whole. If using capsules for a child, follow the specific 'sprinkle' instructions provided by your pharmacist.
Missed Dose
If you miss a dose of Efavirenz, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and continue with your regular schedule. Do not take two doses at once to make up for a missed one. Consistency is vital in HIV treatment to prevent the virus from developing resistance to the medication.
Overdose
Signs of Efavirenz overdose may include increased nervous system symptoms (dizziness, confusion, vivid dreams) and involuntary muscle contractions. If an overdose is suspected, contact a poison control center or seek emergency medical attention immediately. Treatment is supportive, focusing on maintaining vital signs and monitoring the patient's neurological status. Activated charcoal may be used to help remove unabsorbed drug from the gastrointestinal tract.
> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop taking the medication without medical guidance, as this can lead to treatment failure.
⚠️Side Effects
Common Side Effects (>1 in 10)
Efavirenz is well-known for causing central nervous system (CNS) side effects, which affect approximately 50% of patients starting the medication. These symptoms usually appear within the first 1-2 days of therapy and typically resolve or significantly diminish after 2 to 4 weeks of continued use.
Dizziness and Lightheadedness: Patients often describe a 'spinning' sensation or feeling unsteady on their feet.
Vivid or Abnormal Dreams: Many patients report extremely realistic, sometimes intense or strange dreams.
Insomnia: Difficulty falling or staying asleep is common, especially if the drug is not taken at bedtime.
Impaired Concentration: A feeling of 'brain fog' or difficulty focusing on complex tasks.
🔴Warnings
Important Safety Information
Efavirenz is a potent medication that requires strict adherence and careful monitoring. It is essential that patients do not share this medication with others and that they inform all healthcare providers (including dentists and specialists) that they are taking an NNRTI. Because Efavirenz remains in the body for a long time, its effects and potential for drug interactions can persist for weeks after the last dose is taken.
Black Box Warnings
No FDA black box warnings for Efavirenz are currently mandated in the standard 'black box' format, but the 'Warnings and Precautions' section of the FDA label is exceptionally robust regarding psychiatric and hepatic risks. (Note: Older formulations or combination products like Atripla may have boxed warnings related to other components like Tenofovir and Hepatitis B exacerbation).
Major Precautions
Psychiatric Risks: There is a well-documented risk of severe depression, suicide attempts, and aggressive behavior. Patients must be monitored for new or worsening psychiatric symptoms. If you have a history of mental health issues, discuss this thoroughly with your doctor.
🔄Interactions
Contraindicated Combinations (Do Not Use Together)
Efavirenz is a potent inducer of the CYP3A4 enzyme, which means it speeds up the breakdown of many other drugs, making them less effective. Conversely, some drugs can dangerously increase Efavirenz levels. The following must NEVER be used with Efavirenz:
Elbasvir/Grazoprevir: Efavirenz significantly reduces the levels of these Hepatitis C medications, leading to treatment failure.
Midazolam and Triazolam: Efavirenz can alter the metabolism of these sedatives, potentially leading to prolonged sedation or respiratory depression.
Ergot Derivatives (Ergotamine, Dihydroergotamine): Risk of ergot toxicity (vasospasm and ischemia of the extremities).
Pimozide: Increased risk of serious heart rhythm problems (arrhythmias).
🚫Contraindications
Absolute Contraindications
There are specific clinical scenarios where Efavirenz must never be used due to the risk of life-threatening complications:
1Hypersensitivity: Patients with a known, clinically significant hypersensitivity (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis, or erythema multiforme) to Efavirenz or any of its excipients must not take the medication.
2Co-administration with Specific Drugs: As detailed in the interactions section, Efavirenz is contraindicated with drugs that depend heavily on CYP3A4 for clearance and for which elevated plasma concentrations are associated with serious/life-threatening events (e.g., Pimozide, Midazolam).
3Severe Hepatic Impairment: Patients with Child-Pugh Class C liver disease should not use Efavirenz, as the liver cannot process the drug, leading to dangerous accumulation.
👥Special Populations
Pregnancy
Efavirenz is classified as a drug that may cause fetal harm when administered during the first trimester. Historically, it was categorized as FDA Pregnancy Category D.
Teratogenicity: Data from animal studies and some human reports suggested a risk of neural tube defects (like spina bifida). However, more recent and extensive data from the Antiretroviral Pregnancy Registry have shown that the risk of birth defects with Efavirenz is similar to that of other antiretroviral drugs.
Current Guidelines: Most international guidelines (WHO and DHHS) now state that Efavirenz can be used in pregnancy, including the first trimester, if the benefits outweigh the risks. However, women of childbearing potential should be counseled on the potential risks and the importance of effective contraception.
Breastfeeding
In the United States and other regions where clean water and infant formula are available, the CDC and FDA recommend that HIV-infected mothers do not breastfeed
🧬Pharmacology
Mechanism of Action
Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV-1. Its activity is mediated by non-competitive inhibition of the HIV-1 reverse transcriptase (RT) enzyme. It does not inhibit HIV-2 RT or human cellular DNA polymerases alpha, beta, gamma, or delta. The drug binds to a hydrophobic pocket in the p66 subunit of the HIV-1 RT heterodimer. This binding site is distinct from the substrate binding site used by NRTIs. By binding here, Efavirenz acts as a 'molecular wedge' that interferes with the flexibility of the enzyme, preventing it from catalyzing the conversion of viral RNA into DNA. This prevents the formation of the provirus and the subsequent infection of the host cell.
Pharmacodynamics
Antiviral Activity: In cell culture, Efavirenz demonstrates potent activity against most laboratory and clinical isolates of HIV-1.
Resistance: Resistance to Efavirenz can develop rapidly if it is used as monotherapy or if doses are missed. The most common resistance mutation is the K103N mutation in the RT enzyme, which significantly reduces the drug's binding affinity. This mutation also confers cross-resistance to other first-generation NNRTIs like Nevirapine.
Frequently Asked Questions
Common questions about Efavirenz, Lamivudine And Tenofovir Disoproxil Fumarate
What is Efavirenz used for?
Efavirenz is a prescription medication used to treat Human Immunodeficiency Virus type 1 (HIV-1) infection. It belongs to a group of drugs called non-nucleoside reverse transcriptase inhibitors (NNRTIs), which work by blocking a specific enzyme the virus needs to replicate. By lowering the amount of HIV in the body, Efavirenz helps the immune system work better and reduces the risk of HIV-related complications. It is always used in combination with other HIV medicines to prevent the virus from becoming resistant. It is approved for use in adults and children who meet specific weight requirements.
What are the most common side effects of Efavirenz?
The most common side effects of Efavirenz involve the central nervous system and occur in about half of all patients. These include dizziness, insomnia, vivid or unusual dreams, and difficulty concentrating. Many patients also experience a mild skin rash during the first few weeks of treatment. Most of these symptoms appear within the first day or two of starting the medication and usually go away or become much less noticeable after 2 to 4 weeks. Taking the medication on an empty stomach at bedtime can significantly help reduce the severity of these side effects.
Can I drink alcohol while taking Efavirenz?
It is strongly recommended that you avoid or strictly limit alcohol consumption while taking Efavirenz. Alcohol can worsen the dizziness, confusion, and sleepiness that are common side effects of the medication, which can lead to impaired judgment or accidents. Furthermore, both Efavirenz and alcohol are processed by the liver, and combining them may increase the risk of liver damage or inflammation. If you have a history of alcohol use disorder, it is vital to discuss this with your healthcare provider before starting treatment. Always prioritize your safety and the health of your liver by minimizing alcohol intake.
Is Efavirenz safe during pregnancy?
The use of Efavirenz during pregnancy is a complex topic that should be discussed thoroughly with an HIV specialist. While early studies suggested a risk of birth defects like spina bifida, more recent and extensive data indicate that the risk is not significantly higher than with other HIV medications. Current guidelines generally allow for the use of Efavirenz in pregnant individuals if it is the most effective option for controlling the virus. However, if you are planning to become pregnant or find out you are pregnant while taking Efavirenz, contact your doctor immediately. Controlling the virus is essential for both your health and preventing transmission to the baby.
How long does it take for Efavirenz to work?
Efavirenz begins working at the molecular level to block HIV replication shortly after the first dose is taken. However, it takes time for this to translate into a measurable decrease in the 'viral load' in your blood. Most patients will see a significant drop in their viral load within the first 2 to 4 weeks of treatment. The ultimate goal is to reach an 'undetectable' viral load, which typically occurs within 3 to 6 months of consistent, daily use. Regular blood tests will be performed by your doctor to monitor this progress and ensure the medication is working effectively.
Can I stop taking Efavirenz suddenly?
No, you should never stop taking Efavirenz or any other HIV medication suddenly without your doctor's explicit instructions. Stopping the medication allows the HIV virus to begin replicating again, which can lead to a rapid increase in viral load and a drop in CD4 cells (immune cells). More importantly, stopping Efavirenz alone while continuing other medications, or stopping all medications at once, can cause the virus to develop resistance. Because Efavirenz stays in your body for a long time, the virus can 'learn' how to beat it if the levels drop slowly. This could make Efavirenz and similar drugs ineffective for you in the future.
What should I do if I miss a dose of Efavirenz?
If you miss a dose of Efavirenz, take it as soon as you remember, provided it is still the same day. If you do not remember until the next day, skip the missed dose and take your next scheduled dose at the usual time. Do not take two doses at once to make up for the one you missed, as this can increase the risk of side effects. Consistency is the most important factor in HIV treatment; missing doses can allow the virus to multiply and become resistant to the drug. If you find it difficult to remember your doses, talk to your pharmacist about using a pill box or a reminder app.
Does Efavirenz cause weight gain?
Efavirenz itself is not typically associated with significant, rapid weight gain in the same way that some newer HIV medications (like certain integrase inhibitors) might be. However, many patients starting HIV therapy experience 'return-to-health' weight gain as their immune system recovers and the chronic inflammation caused by the virus decreases. Long-term use of Efavirenz has also been linked to lipodystrophy, which is a redistribution of body fat. This can involve losing fat in the face and limbs while gaining fat in the abdominal area or upper back. If you notice significant changes in your weight or body shape, discuss them with your healthcare provider.
Can Efavirenz be taken with other medications?
Efavirenz has many significant drug interactions because it affects how the liver processes other medications. It can make some drugs less effective (like certain birth control pills or Hepatitis C treatments) and can cause others to build up to dangerous levels. It is critical that you provide your doctor and pharmacist with a complete list of all prescription drugs, over-the-counter medicines, vitamins, and herbal supplements (especially St. John's Wort) that you are taking. Your doctor will check for interactions and may need to adjust your dosages or choose different medications to ensure your safety and the effectiveness of your HIV treatment.
Is Efavirenz available as a generic?
Yes, Efavirenz is available as a generic medication in several forms, including the 600 mg tablet and various capsule strengths. Generic versions are required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name version (Sustiva). They are also required to be 'bioequivalent,' meaning they work in the body the same way as the brand-name drug. Choosing a generic can often significantly reduce the cost of HIV treatment. Talk to your pharmacist or insurance provider to see if a generic version of Efavirenz is available and appropriate for you.
Similar Medications
Other drugs with the same active ingredient (Efavirenz)
Rash: A mild-to-moderate skin rash (maculopapular) occurs in about 26% of adults. It usually appears within the first two weeks and often resolves without stopping the drug.
Less Common Side Effects (1 in 100 to 1 in 10)
Nausea and Vomiting: General gastrointestinal upset, which may be mitigated by bedtime dosing.
Fatigue: A persistent sense of tiredness or lack of energy.
Headache: Mild to moderate tension-style headaches.
Hypertriglyceridemia: An increase in the levels of triglycerides (fats) in the blood.
Increased Liver Enzymes: Elevated ALT and AST levels, indicating stress on the liver.
Rare Side Effects (less than 1 in 100)
Gynecomastia: Enlargement of breast tissue in males.
Photosensitivity: Increased sensitivity of the skin to sunlight, leading to easier sunburn.
Tinnitus: Ringing in the ears.
Pancreatitis: Inflammation of the pancreas, which causes severe abdominal pain.
Serious Side Effects — Seek Immediate Medical Attention
> Warning: Stop taking Efavirenz and call your doctor immediately if you experience any of these symptoms. These may indicate life-threatening reactions.
Severe Psychiatric Symptoms: This includes severe depression, suicidal ideation (thoughts of self-harm), or actual suicide attempts. Patients with a history of psychiatric disorders are at higher risk.
Psychosis and Catatonia: Some patients may experience hallucinations, delusions, or a state of unresponsiveness (catatonia).
Hepatotoxicity (Liver Failure): Symptoms include yellowing of the skin or eyes (jaundice), dark urine, pale stools, and pain in the upper right side of the stomach.
Severe Rash (Stevens-Johnson Syndrome): If a rash is accompanied by blistering, fever, mouth sores, or peeling skin, it is a medical emergency.
Convulsions (Seizures): Efavirenz may lower the seizure threshold, especially in those with a history of epilepsy.
QT Prolongation: A heart rhythm disorder that can cause fainting or sudden cardiac arrest.
Long-Term Side Effects
Lipodystrophy: Long-term use of ART, including Efavirenz, has been associated with changes in body fat distribution. This may include loss of fat from the legs, arms, and face (lipoatrophy) and increased fat in the abdomen, upper back ('buffalo hump'), and breasts.
Bone Loss: Some studies suggest a decrease in bone mineral density over years of use, increasing the risk of osteopenia or osteoporosis.
Chronic Cholesterol Elevation: Persistent increases in total cholesterol and LDL ('bad' cholesterol) may require the addition of lipid-lowering medications.
Black Box Warnings
While Efavirenz does not carry a traditional 'Black Box Warning' in the same format as some other drugs (like NRTIs and lactic acidosis), it carries strong boxed warnings in its prescribing information regarding:
1Psychiatric Symptoms: Serious psychiatric adverse experiences, including suicide, delusions, and psychosis-like behavior.
2Nervous System Symptoms: High frequency of dizziness, insomnia, and impaired concentration.
3Embryo-Fetal Toxicity: Potential risk to the fetus if used during the first trimester of pregnancy.
Report any unusual symptoms to your healthcare provider immediately. Do not wait for your next scheduled appointment if you feel your mental health is declining.
Hepatotoxicity: Liver failure has occurred in patients with no pre-existing liver disease. However, the risk is significantly higher in those with Hepatitis B or C co-infection. Liver function tests (LFTs) must be performed before starting and periodically during treatment.
Nervous System Effects: Patients should be warned that the CNS effects (dizziness, confusion) are likely. These are most intense during the first few weeks.
Rash: Most rashes are mild, but Efavirenz must be discontinued if a severe rash with systemic symptoms (fever, blistering) develops.
QT Prolongation: Efavirenz can affect the electrical activity of the heart. Caution is advised in patients taking other medications that prolong the QT interval or those with underlying heart conditions.
Lipid Elevations: Efavirenz can significantly increase cholesterol and triglyceride levels. Baseline lipid testing is required.
Monitoring Requirements
Regular laboratory monitoring is a cornerstone of Efavirenz therapy:
Viral Load and CD4+ Count: To ensure the medication is effectively suppressing the virus.
Liver Function Tests (ALT, AST, Bilirubin): Monitored at baseline and frequently during the first 6 months of therapy.
Lipid Profile: Cholesterol and triglycerides should be checked before starting and periodically thereafter.
Pregnancy Testing: For individuals of childbearing potential, a pregnancy test should be performed before initiation.
Driving and Operating Machinery
Because Efavirenz frequently causes dizziness, sleepiness, and impaired concentration, patients should not drive or operate heavy machinery until they are certain the medication does not affect their ability to perform these tasks safely. These effects are most common in the first few weeks of treatment.
Alcohol Use
Alcohol should be avoided or strictly limited while taking Efavirenz. Alcohol can worsen the central nervous system side effects (dizziness, confusion) and may increase the risk of liver toxicity. Combining alcohol with Efavirenz significantly increases the risk of impaired judgment and coordination.
Discontinuation
Never stop taking Efavirenz without consulting your doctor. Sudden discontinuation can lead to 'viral rebound,' where the amount of HIV in the blood increases rapidly. Furthermore, because Efavirenz has a very long half-life, stopping it while continuing other HIV drugs with shorter half-lives can lead to the virus being exposed to Efavirenz alone, which rapidly leads to drug resistance.
> Important: Discuss all your medical conditions with your healthcare provider before starting Efavirenz, especially any history of liver disease, seizures, or mental health disorders.
St. John’s Wort: This herbal supplement drastically lowers Efavirenz levels in the blood, which can lead to HIV resistance and treatment failure.
Serious Interactions (Monitor Closely)
Statins (Simvastatin, Atorvastatin): Efavirenz may decrease the concentration of these cholesterol drugs. Your doctor may need to adjust the statin dose.
Warfarin: Efavirenz can either increase or decrease the blood-thinning effects of warfarin. Frequent INR (clotting) monitoring is required.
Anticonvulsants (Phenytoin, Carbamazepine): These drugs can lower Efavirenz levels, and Efavirenz can change the levels of the anticonvulsants. Blood level monitoring is essential.
Clopidogrel: Efavirenz may reduce the conversion of clopidogrel to its active form, making it less effective at preventing blood clots.
Voriconazole: Standard doses of voriconazole and Efavirenz cannot be used together; significant dose adjustments are required for both.
Moderate Interactions
Oral Contraceptives: Efavirenz may decrease the effectiveness of hormonal birth control (the pill, patch, or ring). A reliable barrier method (like condoms) should always be used to prevent pregnancy and reduce HIV transmission risk.
Antifungals (Itraconazole, Ketoconazole): Levels of these drugs may be reduced by Efavirenz.
Antibiotics (Clarithromycin): Efavirenz decreases clarithromycin levels; an alternative like azithromycin may be preferred.
Food Interactions
High-Fat Meals: As previously noted, high-fat meals increase the absorption of Efavirenz by nearly 30%. This is not a beneficial increase; it leads to a spike in plasma levels that significantly increases the risk of toxicity and CNS side effects. Always take Efavirenz on an empty stomach.
Grapefruit Juice: While Efavirenz is primarily a CYP2B6 substrate, grapefruit juice (a CYP3A4 inhibitor) could theoretically increase levels, though the clinical impact is less significant than with other HIV drugs.
Herbal/Supplement Interactions
Ginkgo Biloba: May potentially interfere with the metabolism of Efavirenz.
Kava Kava and Valerian Root: These herbs have sedative properties and may worsen the dizziness and somnolence caused by Efavirenz.
Lab Test Interactions
Cannabinoid Screen: Efavirenz can cause a false-positive result for marijuana (cannabinoids) on some rapid urine drug screening tests. If this occurs, a more specific confirmatory test (such as Gas Chromatography-Mass Spectrometry) should be performed to verify the result.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Keep a current list and present it at every medical appointment.
Relative Contraindications
These conditions require a careful risk-benefit analysis by a specialist:
Moderate Hepatic Impairment (Child-Pugh B): Generally avoided unless no other options exist.
History of Severe Psychiatric Disorders: While not an absolute contraindication, a history of psychosis or suicidal behavior requires extreme caution and frequent psychiatric monitoring.
Pre-existing Cardiac Arrhythmias: Specifically those with a history of QT prolongation or those taking other QT-prolonging drugs.
History of Seizures: Efavirenz may increase the frequency of seizures in predisposed individuals.
Cross-Sensitivity
There is no significant evidence of cross-sensitivity between Efavirenz and other classes of HIV medications (like Protease Inhibitors or Integrase Inhibitors). However, there may be a limited risk of cross-reactivity with other NNRTIs (like Nevirapine) regarding skin rashes. If a patient has had a life-threatening rash from another NNRTI, Efavirenz should be used with extreme caution or avoided.
> Important: Your healthcare provider will evaluate your complete medical history, including mental health and liver function, before prescribing Efavirenz.
their infants. This is to avoid the risk of postnatal transmission of HIV to the baby. Additionally, Efavirenz is known to pass into human breast milk, and the effects on a nursing infant are not fully understood.
Pediatric Use
Efavirenz is approved for use in children at least 3 months of age and weighing at least 3.5 kg.
Dosing Challenges: Pediatric dosing must be adjusted frequently as the child grows and gains weight.
CNS Effects: Children may experience similar CNS side effects as adults, but they may manifest as irritability or behavioral changes. Parents should monitor their child’s school performance and mood closely.
Rash: Rash is more common in children than in adults and should be reported to a pediatrician immediately.
Geriatric Use
Clinical experience in patients aged 65 and older is limited.
Pharmacokinetics: Older adults may have reduced hepatic and renal function, which can affect drug metabolism.
Polypharmacy: Elderly patients are often on multiple medications for other conditions (hypertension, heart disease), increasing the risk of significant drug-drug interactions.
Cognitive Impact: The CNS effects of Efavirenz (confusion, dizziness) may be more pronounced in older adults and could be mistaken for age-related cognitive decline.
Renal Impairment
As less than 1% of the drug is excreted by the kidneys, no dose adjustment is required for patients with renal insufficiency. However, patients on dialysis should still be monitored for overall tolerance of the ART regimen.
Hepatic Impairment
Mild (Child-Pugh A): No dose adjustment, but monitor for CNS toxicity.
Moderate to Severe (Child-Pugh B or C): Not recommended. If used in moderate cases, extreme caution and frequent LFT monitoring are mandatory.
> Important: Special populations require individualized medical assessment and frequent follow-up to ensure safety and efficacy.
Relationship to Side Effects: There is a clear relationship between higher plasma concentrations and the frequency of CNS side effects. This is why empty-stomach dosing is critical.
Pharmacokinetics
| Parameter | Value |
|---|---|
| Bioavailability | Increased by 28% with high-fat meal |
| Excretion | Fecal (16-61%), Renal (14-34% as metabolites) |
Chemical Information
Molecular Formula: C14H9ClF3NO2
Molecular Weight: 315.67 g/mol
Solubility: Practically insoluble in water (<10 micrograms/mL).
Structure: Efavirenz is chemically described as (S)-6-chloro-4-(cyclopropylethynyl)-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one. It is a white to slightly pink crystalline powder.
Drug Class
Efavirenz is a Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI). Related medications in this class include Nevirapine (Viramune), Delavirdine (Rescriptor), Etravirine (Intelence), Rilpivirine (Edurant), and Doravirine (Pifeltro). Efavirenz is considered a 'first-generation' NNRTI.