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Isentress

Isentress: Raltegravir Overview

Isentress is a branded medication that contains the active ingredient raltegravir. It belongs to the integrase inhibitor class of antiretroviral drugs used to treat HIV-1 infection. In the United Kingdom Isentress is available as a 400 mg film-coated tablet (tab) and is prescribed only by a qualified healthcare professional.

Roughly, the medication is classified as a prescription-only medicine (POM) and is regulated by the Medicines and Healthcare products Regulatory Agency (MHRA). The tablet can be taken with or without food, but specific timing with certain other medicines is important to preserve its effectiveness.

How Raltegravir Works in the Body

• Target: Raltegravir blocks the HIV-1 integrase enzyme, which the virus needs to insert its genetic material into the host’s DNA.
• Result: By preventing this integration step, the drug stops new virus particles from being produced, reducing the amount of HIV in the bloodstream.
• Pharmacokinetics: After oral administration, raltegravir reaches peak plasma concentrations in about 1-3 hours. It is metabolised mainly by glucuronidation (UDP-glucuronosyltransferase 1A1) and eliminated through urine and faeces.
• Onset and Duration: Antiviral activity begins within a few days of starting therapy, and steady-state levels are achieved after about 2 days of twice-daily dosing.

Conditions Treated with Isentress

• Primary indication: Treatment of HIV-1 infection in adults and adolescents when combined with other antiretroviral agents.
• Guideline use: The UK’s BHIVA (British HIV Association) and NHS guidelines recommend raltegravir as part of a combined antiretroviral regimen for patients who are antiretroviral-naïve or who need a switch due to resistance, intolerance, or drug-interaction concerns.

Off-Label and Investigational Applications

Current UK-approved labelling does not list any off-label uses for raltegravir. Emerging research has explored raltegravir in pre-exposure prophylaxis (PrEP) and in pregnant women with high viral loads, but these applications remain investigational and are not sanctioned by the MHRA. Use outside the approved indication should only occur under specialist supervision and with a clear risk-benefit assessment.

Who Should (and Should Not) Use Isentress?

Absolute Contraindications

• Known hypersensitivity to raltegravir or any tablet excipient.

Relative Contraindications & Cautions

• Pregnancy: Raltegravir is considered safe and is often continued during pregnancy, but the decision should be individualised.
• Breastfeeding: Limited data; benefits and risks must be weighed.
• Severe liver disease: Use with caution; monitor liver enzymes.

Special Populations

• Renal impairment: No dose adjustment needed for mild-to-moderate kidney disease.
• Hepatic impairment: No formal dose change, but regular liver function monitoring is advised.
• Elderly: No specific dosage change, but consider comorbidities and polypharmacy.

Safety Profile: Side Effects and Interactions

Common Side Effects

• Nausea
• Diarrhoea
• Headache
• Fatigue
• Insomnia

These events are usually mild and transient; they often improve with continued therapy.

Serious Adverse Events

• Severe allergic reactions (rash, angio-oedema, anaphylaxis) - seek emergency care.
• Liver enzyme elevations (ALT/AST) - monitor regularly, especially in patients with hepatitis co-infection.
• Rhabdomyolysis (muscle breakdown) - rare, but patients should report unexplained muscle pain or dark urine.
• Immune reconstitution inflammatory syndrome (IRIS) - can occur after viral suppression begins.

Drug Interactions

• UGT1A1 inducers (e.g., rifampicin, carbamazepine) increase raltegravir clearance - dose may need to be doubled to 800 mg twice daily.
• UGT1A1 inhibitors (e.g., atazanavir) may raise raltegravir levels - monitor for toxicity.
• Antacids containing aluminium or magnesium (e.g., Maalox®, Gaviscon®) - take raltegravir at least 2 hours before or after the antacid.
• Dolutegravir, elvitegravir, other integrase inhibitors - co-administration is not recommended due to overlapping mechanisms.

Food and Lifestyle Interactions

• Raltegravir can be taken with or without food; however, a high-fat meal may modestly increase absorption, which is not clinically significant.
• Alcohol does not have a direct pharmacological interaction, but excessive intake can worsen liver toxicity.
• No known impact on driving or operating machinery, but severe side effects (e.g., dizziness) may affect safety.

How to Take Isentress

• Standard dosing: One 400 mg tablet twice daily (approximately every 12 hours).
• Dose adjustment for enzyme inducers: Increase to 800 mg twice daily if taking strong UGT1A1 inducers such as rifampicin.
• Special populations: No routine adjustments for renal or hepatic impairment, but follow specialist advice if severe liver disease is present.

Administration Tips

• Swallow the tablet whole; do not crush or chew.
• Keep the dose schedule consistent; missing a dose should be followed by taking the missed dose as soon as remembered, unless the next scheduled dose is near, in which case skip the missed dose. Do not double-dose.
• Store tablets at 20-25 °C (68-77 °F), protected from moisture and light.

Overdose Management

• Symptoms may include nausea, vomiting, dizziness, and rapid heart rate.
• If an overdose is suspected, seek immediate medical attention; supportive care and monitoring are the mainstays of treatment. No specific antidote exists.

Discontinuation

• No tapering is required; however, abrupt cessation can lead to viral rebound.
• Patients should discuss any plan to stop therapy with their HIV specialist to arrange a suitable alternative regimen.

Monitoring and Follow-Up

• Baseline labs before starting: CD4 count, HIV viral load, liver function tests, renal function, and hepatitis B/C status.
• During therapy: Viral load is typically checked at 4 weeks, then every 12 weeks once suppressed. Liver enzymes should be monitored at baseline and periodically, especially if co-infected with hepatitis.
• Clinical review: Evaluate adherence, side-effect burden, and any new medications at each visit.

Storage and Handling

• Keep the bottle tightly closed and store at room temperature, away from direct sunlight and moisture.
• Do not use tablets after the expiration date printed on the packaging.
• Dispose of unused medication via a pharmacy take-back scheme or according to local waste-disposal guidelines to prevent accidental ingestion.

Medication-Specific Glossary

Integrase inhibitor

A class of antiretroviral drugs that block the HIV integrase enzyme, preventing viral DNA from integrating into host cells.

Viral load

The quantity of HIV RNA copies per millilitre of blood; a key indicator of treatment effectiveness.

Glucuronidation

A metabolic pathway where the liver adds a glucuronic acid moiety to a drug, enhancing its water solubility for excretion.

UGT1A1

The enzyme (uridine diphosphate glucuronosyltransferase 1A1) responsible for raltegravir’s primary metabolism; its activity can be altered by other medicines.

Medical Disclaimer

This article provides educational information about Isentress (raltegravir) and is not a substitute for professional medical advice. Treatment decisions, including the use of any medication for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes only and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.