Sulfonamides etc. Flashcards
What is the strucutre of sulfonamides?
Similar to PABA, a precursor required by bacteria for folic acid synthesis
What is the MoA for sulfonamides?
Stop bacteria from synthesizing folic acid
Bacteriostatic
How are sulfonamides excreted?
Renal
Extent varies with each agent
What are the ADRs for sulfonamides?
Anaphylaxis
Cutaneous reactions
Hematologic
Hypersensitivity
Nephrotoxicity
Kernicterus
What are the mechanisms of resistant against sulfonamides?
Over production of PABA (Neisseria, Staph)
Structureal change in dihydropteroate synthetase
Decreased permeability of the bacteria to the drug
What are the indications for sulfonamides?
Acute, uncomplicated UTI
Pneumocystis carinii
Nocardosis
Toxoplasmosis
Malaria
Rheumatic fever
What is the MoA for trimethoprim?
Inhibits dihydrofolate reductase, preventing THF formation
Bacteriostatic or bactericidal depending on the growth conditions
How is trimethoprim excreted?
80% unchanged via glomerular filtration and tubular secretion
What are the ADRs of trimethoprim?
Cutaneous rxns
GI rxns
Hematologic rxns
Caution in patients with foalte deficiency
What are the indications for trimethoprim?
Acute uncomplicated UTI
Recurrent UTI prophylaxis
Traveler’s diarrhea
What is the MoA of bactrim?
Trimethoprim/sulfamethoxazole
Combined mechanisms of both agents, usually bactericidal
What are the indications for bactrim?
UTI
RTI - COPD, Pneumonia, Sinusitis
GI infections - Slmonella/shigella, traveler’s diarrhea, cholera
STDs
Stenotrophomonas maltophilia
What are the drug interactions associated with bactrim?
Warfarin - potentiation
Methorexate - increase free fraction
What is the MoA for Nitrofurantoin?
Possibly interferes with early stages of bacterial carb metabolism
Possibly production of free radicals
What is the distribution and excretion for Nitrofurantoin?
Distribution - High urine concentrations
Excretion - rate is linearly related to GFR
What are the ADRs of Nitrofurantoin?
Hypersensitivity
Hematologic
Hepatotoxicity
Peripheral neuropathy
GI
What are the pulmonary ADRs of nitrofurantoin?
Acute - hypersensitivity
Subacute - after 1 month, cough, dyspnea, interstitial infiltrate
Chronic - cough, dyspnea, interstitial infiltrate
Often reversible, but not necessarily and can be fatal
What is nitrofurantoin indicated for?
Acute uncomplicated UTI
UTI prophylaxis
What is the MoA for methenamine?
At adequate urine pH (<5.5), its hydrolyzed to formaldehyde, which kills bacteria by denaturing proteins
What is the absorption and excretion of methenamine?
Absorption - rapidly absorbed in GI tract, excellant bioavailability
Excretion - Renal clearance is 95% of total, half life = 3-4hrs
What are the ADRs for methenamine?
Hypersensitivity
Hemorrhagic Cystitis
GI
Avoid in hepatic insufficiency
Renal failure
What is the spectrum of methenamine?
Virtually all bacteria and fungi
Certain urease positive bacteria can alkalinize the urine
What are the indications for methenamine?
UTI prophylaxis only
