Mechanism of action of Zidovudine and Dapsone

 

Zidovudine (AZT)

Mechanism of Action: Zidovudine is an antiretroviral medication used primarily for the treatment of HIV infection. It belongs to the class of drugs known as nucleoside reverse transcriptase inhibitors (NRTIs). Its mechanism of action is as follows:

1. Inhibition of Reverse Transcriptase: HIV relies on the enzyme reverse transcriptase to convert its RNA into DNA, which is then integrated into the host cell’s genome. Zidovudine acts as a thymidine analog and is phosphorylated inside the cell to its active triphosphate form, zidovudine triphosphate (ZDV-TP).

2. Chain Termination: ZDV-TP competes with the natural thymidine triphosphate for incorporation into the viral DNA. Once ZDV-TP is incorporated, it lacks a 3’-hydroxyl group, which prevents the addition of further nucleotides, leading to premature termination of the DNA chain and thus halting viral replication.

Dapsone

Mechanism of Action: Dapsone is an antibacterial and antiprotozoal agent mainly used to treat leprosy, dermatitis herpetiformis, and as prophylaxis or treatment for Pneumocystis jirovecii pneumonia (PCP) in immunocompromised patients (e.g., those with HIV). Its mechanism of action involves:

1. Inhibition of Dihydropteroate Synthase: Dapsone is a sulfone drug that inhibits dihydropteroate synthase, an enzyme involved in the synthesis of folic acid in bacteria and protozoa. Folic acid is necessary for the synthesis of nucleic acids, and by inhibiting its production, dapsone interferes with DNA synthesis, leading to impaired bacterial growth.

2. Anti-inflammatory Action: In conditions like dermatitis herpetiformis, dapsone’s anti-inflammatory properties also play a role by reducing neutrophil migration and activity, which mitigates tissue damage and inflammation.

While zidovudine primarily targets viral replication in HIV, dapsone acts on bacterial/protozoal organisms and exhibits anti-inflammatory effects, making both drugs valuable in the treatment and prevention of infections in immunocompromised patients.