Efavirenz

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Generic Name of Efavirenz - Learn More

Efavirenz

Efavirenz Precaution - What You Need to Know

Efavirenz is an antiretroviral medication primarily used for the treatment of HIV (human immunodeficiency virus) infection. When prescribing efavirenz, several precautions must be taken into account. Efavirenz is known to cross the placenta and is categorized as a Category D drug for pregnancy. This classification indicates that there is evidence of human fetal risk, and it should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus. In particular, the first trimester should be avoided unless necessary due to risks like neural tube defects.

For breastfeeding women, efavirenz can pass into breast milk, and the potential risk to the infant must be considered. Therefore, it is advised that breastfeeding should be avoided during treatment with efavirenz.

Efavirenz has psychiatric and neurological side effects, including depression, anxiety, and suicidal thoughts, and can exacerbate conditions such as severe depression or psychosis. It is crucial to screen patients for a history of mental health disorders prior to starting efavirenz. Caution should also be exercised in individuals with a history of seizures, as efavirenz can lower the seizure threshold.

Regular liver function testing should be conducted, as efavirenz is metabolized by the liver, and liver toxicity may occur. This drug should be used with caution in patients with hepatitis or severe liver disease.

Efavirenz Indication - Uses and Benefits

Efavirenz is primarily used as part of combination therapy for the treatment of HIV-1 infection. It is an NNRTI (non-nucleoside reverse transcriptase inhibitor) that works by binding directly to the reverse transcriptase enzyme, preventing the conversion of viral RNA into DNA, which is an essential step in the replication of HIV. Efavirenz is generally used in combination with other antiretrovirals (e.g., NRTIs, protease inhibitors) to reduce the viral load and increase the CD4 count.

Efavirenz is particularly indicated in treatment-naive patients or in patients switching from other therapies. It is often included in the first-line therapy regimens for HIV in combination with other antiretrovirals.

Off-label uses of efavirenz include its use in post-exposure prophylaxis (PEP) for HIV prevention in high-risk individuals. It has also been explored for use in pre-exposure prophylaxis (PrEP), but it is not typically preferred due to its side effect profile.

Efavirenz Contraindications - Important Warnings

Efavirenz is contraindicated in individuals with known hypersensitivity to the drug or any of its components. Patients with a history of severe hepatic impairment, active hepatitis, or liver failure should not use efavirenz due to the potential for liver toxicity.

Efavirenz is contraindicated in patients who are taking teratogenic drugs during pregnancy, as it can cause birth defects in the fetus, particularly in the first trimester. Therefore, it is contraindicated in pregnancy unless no alternatives are available. Women who are pregnant or planning to become pregnant should not start efavirenz therapy.

Because of its CNS effects, including dizziness, insomnia, and psychiatric symptoms, efavirenz should be used cautiously in patients with a history of mental health disorders. It is also contraindicated in patients with active psychiatric disorders (including severe depression, psychosis, or suicidal ideation), as these conditions could worsen during treatment.

Efavirenz Side Effects - What to Expect

Efavirenz's side effects can be mild, moderate, or severe, and they are often related to its effects on the central nervous system. Common adverse effects include dizziness, insomnia, headaches, and fatigue. These effects often occur during the first few weeks of therapy and may subside as the patient adjusts to the medication.

Serious side effects can include psychiatric disturbances, such as depression, suicidal thoughts, and psychosis. Efavirenz is associated with an increased risk of neuropsychiatric side effects, particularly in individuals with a history of mental health disorders. The drug can also cause liver enzyme elevations, and in rare cases, hepatotoxicity.

Efavirenz may cause rash, which is generally mild but can sometimes progress to severe reactions like Stevens-Johnson syndrome. Liver toxicity, including hepatitis, can occur, and liver function should be monitored regularly.

Other less common side effects include gastrointestinal symptoms (nausea, vomiting), dyslipidemia (elevated cholesterol), and hyperglycemia.

Efavirenz Pregnancy Category ID - Safety Information

4

Efavirenz Mode of Action - How It Works

Efavirenz works as a non-nucleoside reverse transcriptase inhibitor (NNRTI) by directly binding to the reverse transcriptase enzyme, which is essential for the replication of HIV-1. By binding to reverse transcriptase, efavirenz causes a conformational change that inhibits the enzyme’s activity. This prevents the conversion of HIV RNA into DNA, a crucial step in the viral replication process, thereby reducing the amount of HIV in the blood and other tissues.

The pharmacokinetics of efavirenz involve rapid absorption with peak plasma levels occurring approximately 3–5 hours after oral administration. It is highly protein-bound and metabolized by the liver via CYP3A4, CYP2B6, and other cytochrome P450 enzymes. Efavirenz has a long half-life of about 52-76 hours, allowing for once-daily dosing.

Efavirenz’s interaction with the cytochrome P450 system can affect the metabolism of other drugs, which may require dose adjustments when used concurrently.

Efavirenz Drug Interactions - What to Avoid

Efavirenz has significant drug-drug interactions that should be carefully managed. It is a strong inducer of the cytochrome P450 enzyme system (CYP3A4) and can affect the metabolism of many other drugs. For example, efavirenz can reduce the effectiveness of oral contraceptives, requiring the use of additional contraception methods.

It can also decrease the levels of drugs such as methadone, simvastatin, warfarin, and certain anticonvulsants, which may necessitate dose adjustments of these medications. The co-administration of st. john’s wort (a herbal supplement) can significantly reduce efavirenz plasma concentrations and should be avoided.

In contrast, efavirenz may increase the concentration of other drugs, particularly benzodiazepines, phenytoin, and certain antifungal medications. Careful monitoring of drug levels is recommended when co-administering these drugs.

Patients taking antacids, H2 blockers, or proton pump inhibitors should be monitored for potential reduced efavirenz absorption.

Efavirenz Adult Dose - Recommended Dosage

For adults, the standard dose of efavirenz is typically 600 mg once daily, administered on an empty stomach, usually at night, to minimize CNS-related side effects such as dizziness and insomnia. It is often used in combination with other antiretroviral agents as part of a combination regimen to treat HIV.

The dose should not exceed 600 mg daily, and dose adjustments are usually unnecessary in patients with normal renal function. For patients with hepatic impairment, dose adjustments may be required, and liver function should be monitored closely.

Efavirenz Child Dose - Dosage for Children

Efavirenz is not recommended for children under 3 years old due to safety concerns. For children aged 3 years and older, the dosing is based on body weight:

- 10 mg/kg once daily for children weighing < 25 kg.
- 600 mg once daily for children weighing ≥ 25 kg.

As with adults, efavirenz should be administered on an empty stomach, preferably at bedtime to minimize central nervous system effects. Monitoring for psychiatric side effects is particularly important in the pediatric population. Regular monitoring of liver function and viral load is essential to assess the efficacy and safety of therapy in children.

In summary, Efavirenz is a powerful NNRTI used in combination with other antiretrovirals to treat HIV. However, it requires careful management, particularly in pregnancy, individuals with mental health disorders, and those with liver dysfunction. Regular monitoring is essential for efficacy and safety.

Efavirenz Renal Dose - Dosage for Kidney Conditions

Efavirenz is primarily metabolized by the liver, and renal impairment does not significantly affect its pharmacokinetics. Therefore, no dose adjustment is necessary for patients with mild to moderate renal impairment.

However, in patients with severe renal impairment or end-stage renal disease (ESRD) on dialysis, careful monitoring is recommended as the drug may accumulate, potentially increasing the risk of side effects. In these cases, consultation with an HIV specialist for alternative treatments may be necessary.