Ch. 88: Sulfonamides and Trimethoprim

why is Trimethoprim/sulfamethoxazole (TMP/SMZ) a good combination?*

*Inhibits sequential steps in bacterial folic acid synthesis, making it much more powerful than TMP or SMZ alone

adverse effects of trimethoprim

-Hematologic effects -Hyperkalemia -don't Use in pregnancy and lactation

adverse effects of sulfonamides

-Hypersensitivity reactions: Stevens-Johnson syndrome, photosensetitivity -Hematologic effects -*Kernicterus (fetal damage) -*Renal damage from crystalluria

adverse effects of TMP/SMZ [Bactrim] or [Septra]

-Nausea and vomiting -Rash -Hyperkalemia -Hypersensitivity reactions (Stevens-Johnson syndrome) -Blood dyscrasias -Kernicterus -Renal damage: Crystalluria

drug interactions of sulfonamides

-can increase the levels of warfarin and phenytoin

A patient who sustained second- and third-degree burns has been prescribed mafenide. Which statement about mafenide does the nurse identify as true? A. Use of mafenide can cause alkalosis. B. Mafenide is painful upon application. C. A blue-green to gray discoloration of the skin occurs with mafenide therapy. D. Mafenide exerts its therapeutic effect by the release of free silver.

B: Local application of mafenide is frequently painful. Mafenide is metabolized to a compound that can suppress renal excretion of acid, thereby causing acidosis. Silver sulfadiazine, another topical sulfonamide used for burn therapy, can cause a blue-green to gray skin discoloration, so facial application should be avoided. Mafenide does not cause this specific skin discoloration. Mafenide acts by the same mechanism as other sulfonamides. In contrast, the antibacterial effects of silver sulfadiazine are due primarily to the release of free silver, not to the sulfonamide portion of the molecule.

A patient who takes warfarin has been prescribed sulfadiazine. When teaching the patient about this drug, which statement will the nurse include? A."If you become pregnant, it is safe to take sulfadiazine." B."You should limit your fluid intake while taking sulfadiazine." C."Avoid prolonged exposure to sunlight, wear protective clothing, and apply a sunscreen to exposed skin." D."You will most likely need to have an increase in the dose of warfarin while taking sulfadiazine."

C: Sulfonamides can cause photosensitivity

A patient who was taking sulfonamides develops Stevens-Johnson syndrome. Upon assessment, the nurse expects to find what? A. Hypotension B. Bronchospasm C. Temperature of 35.5º C D. Widespread skin lesions

D: The most severe hypersensitivity response to sulfonamides is Stevens-Johnson syndrome, a rare reaction with a mortality rate of about 25%. Symptoms include widespread lesions of the skin and mucous membranes, combined with fever, malaise, and toxemia. Bronchospasm and hypotension, as well as tachycardia, are manifestations of anaphylactic reactions.

*what is the mechanism of action of trimethoprim and sulfonamides? are they bacteriocidal or bacteriostatic?

Suppress bacterial growth by inhibiting tetrahydrofolic acid, a derivative of folic acid or folate, so they're bacteriostatic

what type of infection are sulfonamides primarily used for?

UTIs

therapeutic uses of TMP/SMZ [Bactrim] or [Septra]

UTIs, ear infections, bronchitis (just remember in general it is for Gram-negative)

use of Trimethoprim

acute UTIs

*are sulfonamides and trimethoprim broad or narrow spectrum antibiotics?

broad spectrum

use of Silver sulfadiazine and mafenide

suppress bacterial colonization in patients with second- and third-degree burns