Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor (NtRTI). Its mechanism differs from nucleoside analogues (NRTIs) because:

• A TDF does not require any intracellular phosphorylation to become active
• B TDF inhibits HIV integrase rather than reverse transcriptase
• C TDF acts as a non-competitive allosteric inhibitor of reverse transcriptase, unlike chain terminators
• D TDF is a prodrug of tenofovir, an acyclic nucleoside phosphonate that requires only two (not three) intracellular phosphorylation steps to become the active diphosphate ✓

Explanation

Tenofovir disoproxil fumarate is a prodrug of tenofovir, which is itself an acyclic nucleoside phosphonate — it already contains one phosphate group in its structure. Therefore, it requires only two (not three) kinase-mediated phosphorylation steps to become tenofovir diphosphate, the active form that competes with dATP and acts as a chain terminator of reverse transcriptase. Traditional NRTIs (like zidovudine) start without phosphate and need all three phosphorylation steps. TDF does not inhibit integrase (which is the target of dolutegravir/raltegravir) and is not a non-competitive inhibitor.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.