💊 Antiretrovirals (HIV)

Antiretrovirals (ARVs) are a diverse group of drugs used in combination to treat human immunodeficiency virus (HIV) infection. They target various stages of the viral life cycle, aiming to suppress viral replication and improve immune function.

ARVs are categorised by their targets: Nucleoside/tide Reverse Transcriptase Inhibitors (NRTIs/NtRTIs) block reverse transcription; Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) also inhibit reverse transcriptase but at a different site; Protease Inhibitors (PIs) prevent viral protein cleavage; Integrase Strand Transfer Inhibitors (INSTIs) block integration of viral DNA into host genome; Entry Inhibitors prevent viral entry into cells.

Antiretroviral therapy (ART) is indicated for all individuals diagnosed with HIV infection, regardless of CD4 count, to reduce morbidity, mortality, and prevent onward transmission. It is also used for post-exposure prophylaxis (PEP) and pre-exposure prophylaxis (PrEP) in specific high-risk situations to prevent HIV acquisition.

Hypersensitivity to any component of the ARV regimen is an absolute contraindication. Specific ARVs may have contraindications related to severe hepatic or renal impairment, or significant drug-drug interactions. Pregnancy and breastfeeding require careful consideration of drug choice but are not contraindications to ART itself.

Adverse effects vary widely by drug class. Common issues include gastrointestinal upset (nausea, diarrhoea), fatigue, and headache. Specific concerns include renal toxicity (e.g., tenofovir disoproxil fumarate), hepatotoxicity, lipodystrophy, metabolic abnormalities (e.g., PIs), and neuropsychiatric effects (e.g., efavirenz). Hypersensitivity reactions can occur with some agents.

Regular monitoring of viral load (HIV RNA) and CD4 cell count is crucial to assess treatment efficacy and immune status. Renal and liver function tests, full blood count, and metabolic parameters (lipids, glucose) should be monitored due to potential drug toxicities. Adherence to therapy is also continuously assessed.

Prescribing ARVs requires meticulous attention to drug interactions, as many ARVs are metabolised by CYP450 enzymes. Always check for allergies and co-morbidities that might influence drug choice (e.g., renal impairment, cardiovascular risk). Patient counselling on adherence, potential side effects, and the importance of regular monitoring is paramount.

High-yield facts include the concept of combination therapy ('HAART' or 'ART') and the goal of achieving an undetectable viral load. Understand the main drug classes and their targets in the viral life cycle. Remember the importance of ART for prevention (TasP - Treatment as Prevention, PrEP, PEP). Adherence is key to preventing resistance.

SBA questions often test the understanding of different ARV drug classes and their mechanisms of action. Scenarios might involve choosing an appropriate regimen based on patient comorbidities, drug interactions, or resistance profiles. Questions on PEP/PrEP indications and the importance of adherence are also common. Identifying specific adverse effects linked to particular drug classes is high-yield.