Dolutegravir is preferred over raltegravir as an integrase strand transfer inhibitor (INSTI) in second-line ART regimens. The pharmacological basis for dolutegravir's superiority against INSTI-resistant HIV is:

• A Dolutegravir inhibits reverse transcriptase in addition to integrase, providing a dual mechanism unlike raltegravir
• B Dolutegravir has a longer dissociative half-life from the integrase-DNA complex (residence time >71 hours vs. <1 hour for raltegravir), making it much harder for resistance mutations to dislodge it ✓
• C Dolutegravir is not metabolized by CYP enzymes, avoiding resistance through drug-level reduction
• D Dolutegravir binds the catalytic HHCC zinc finger motif rather than the DDE catalytic core, escaping INSTI cross-resistance mutations

Explanation

The critical pharmacodynamic distinction between second-generation INSTIs (dolutegravir, bictegravir) and first-generation INSTIs (raltegravir, elvitegravir) is the prolonged residency time on the integrase-viral DNA complex. Raltegravir's off-rate from the complex is rapid (residence time <1 hour), allowing resistance mutations (Q148H/K/R, N155H, G140S) to provide sufficient steric disruption to displace the drug. Dolutegravir's bicyclic hydroxypyrimidinone scaffold engages more binding contacts with a longer off-rate (t1/2 > 71 hours), requiring 2–3 accumulated mutations to achieve clinically significant resistance — explaining its efficacy against many INSTI-resistant strains. It is metabolized primarily by UGT1A1 with a minor CYP3A4 component.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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