Antimicrobials I Flashcards
What are the two antimetabolites? What are their mechanisms?
Trimethoprim: dihydrofolate reducates inhibitor; it prevents folic acid from being reduced: DHF –> THF.
Sulfamethoxazole: dihydropterate synthase inhibitor: prevents pteridine + PABA –> dihydropteric acid.
Often used together (Bactrim)
What is a complication of Trimethoprim?
Hyperkalemia in patients with renal insufficiency.
What three drugs are used for TB?
Isoniazid, pyrazinamide, ethambutol
What is the mechanism of Isoniazid?
Binds enol-acyl carrier protein reductase (InhA), preventing synthesis of mycolic acid; prodrug
What is the mechanism of Pyrazinamide?
Targets fatty acid synthase I in mycolic acid synthesis (no more protection inside macrophage).
What is the mechanism of Ethambutol?
Inhibits arabinosyl transferases involved in cell wall biosynthesis.
What can you do to prevent the neurologic symptoms of Isoniazid?
Co-administer with B6.
What are the side effects of Pyrazinamide?
Elevates uric acid (gout predisposition), centrilobular hepatitis
What are the side effects of Ethambutol?
Dose-dependent optic neuritis: loss of ability to differentiate red and green. Elevates uric acid (gout predisposition).
What are the two purine analogs? What is their mechanism?
Acyclovir, ganciclovir
Binds to enzymes, which produce inactive compounds, stopping nucleic acid synthesis.
What are side effects of Ganciclovir?
Neutropenia, thrombocytopenia, adverse CNS effects
What is Acyclovir used for?
HSV, VZV (higher doses)
What is Ganciclovir used for?
CMV, retinitis in HIV
What is the mechanism of Foscarnet? What is it used for?
Binds to enzymes, which produces inactive compounds, stopping nucleic acid synthesis (highly ionized- no oral utility, renal excretion)
Broad spectrum (HSV, VZV, CMV and RNA viruses, including HIV). Used for invasive HSV/VZV infections from acyclovir-resistant strains. Alternative to ganciclovir for CMV.
Renal/CNS toxicities.
