Etravirine

BRAND NAMES

1. Intelence – the most widely recognized original brand name 

2. Etravirine Tablets – used as a generic or descriptive labeling in some regions.

MECHANISM OF ACTION

Etravirine is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that works by binding directly to the HIV-1 reverse transcriptase enzyme at a site distinct from the nucleoside binding site. This binding induces a conformational change in the enzyme, which inhibits its ability to transcribe viral RNA into DNA, thereby preventing viral replication.

PHARMACOKINETICS

Absorption

Etravirine is well absorbed orally, with peak plasma concentrations typically reached 4–5 hours after ingestion. Its bioavailability is enhanced when taken with food, so it is recommended to take the drug with a meal to improve absorption.

Distribution

Etravirine has a moderate volume of distribution, typically around 2.5–4 L/kg, indicating that the drug distributes beyond the bloodstream into body tissues but is largely retained in the plasma due to high protein binding (~99%).

Metabolism

Etravirine is extensively metabolized in the liver, primarily by the cytochrome P450 enzymes CYP3A4, CYP2C9, and CYP2C19. It undergoes oxidation and glucuronidation, resulting in inactive metabolites that are subsequently excreted.

Elimination

Etravirine is eliminated primarily through hepatic metabolism, with less than 1% excreted unchanged in the urine. The metabolites are mainly excreted via feces and, to a lesser extent, in urine. 

PHARMACODYNAMICS

Etravirine exerts its pharmacodynamic effect by inhibiting the HIV-1 reverse transcriptase enzyme, a critical enzyme for viral replication. By binding to a non-nucleoside allosteric site on the enzyme, etravirine induces a conformational change that prevents the conversion of viral RNA into DNA, effectively halting viral replication.

ADMINISTRATION

Etravirine is administered orally in tablet form and is typically taken twice daily. It should be taken with food to enhance absorption and achieve optimal plasma concentrations. Tablets must be swallowed whole and should not be crushed, chewed, or broken, as this can affect drug release and bioavailability.

DOSAGE AND STRENGTH

Etravirine is generally prescribed as 200 mg taken orally twice daily in combination with other antiretroviral agents for the treatment of HIV-1 infection. Tablets are available in a strength of 100 mg, so the standard twice-daily dose is achieved by taking two 100 mg tablets per dose.

DRUG INTERACTIONS

Etravirine is subject to multiple drug interactions due to its metabolism by CYP3A4, CYP2C9, and CYP2C19 enzymes. Concomitant use of CYP3A4 inducers such as rifampin, carbamazepine, or phenytoin can reduce etravirine plasma levels and decrease its antiviral effectiveness, while CYP3A4 inhibitors like ketoconazole or itraconazole may increase drug levels, raising the risk of side effects including rash or hepatic toxicity.

FOOD INTERACTIONS

Etravirine should be taken with food, as meals enhance its oral absorption and increase plasma concentrations, improving antiviral efficacy. Taking it without food may reduce bioavailability and result in lower systemic drug levels.

CONTRAINDICATIONS

Etravirine is contraindicated in patients with a known hypersensitivity to etravirine or any component of the formulation. It should also be avoided in individuals with severe hepatic impairment, as impaired liver function can reduce metabolism and increase the risk of toxicity.

SIDE EFFECTS

Gastrointestinal:

1. Nausea 

2. Vomiting 

3. Diarrhea 

4. Abdominal discomfort

OVER DOSAGE   

An overdose of Etravirine can intensify its known adverse effects, including severe rash, gastrointestinal disturbances, liver enzyme elevations, fatigue, dizziness, and headache. There is no specific antidote for etravirine overdose, so management is primarily supportive.

TOXICITY

Etravirine exhibits toxicity that is generally mild to moderate, with the most common effects involving the skin, liver, and gastrointestinal system. Dermatologic reactions such as rash are the most frequently reported, ranging from mild irritation to rare severe hypersensitivity reactions.