Chapter 88
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.
Answer: B Rationale: 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."
Answer: C Rationale: Patients taking sulfadiazine should be advised to avoid prolonged exposure to sunlight, wear protective clothing, and apply a sunscreen to exposed skin. Sulfonamides can cause kernicterus in newborns. These drugs should not be administered to pregnant women near term, nursing mothers, or infants under 2 months old. Sulfadiazine causes deposition of sulfonamide crystals, which can injure the kidney. To minimize crystalluria, hydration should be sufficient to produce a daily urine flow of 1200 mL in adults; alkalinization of urine (for example, with sodium bicarbonate) can also help. Patients taking sulfadiazine should drink 8 to 10 glasses of water per day. Sulfonamides can intensify the effects of warfarin, phenytoin, and sulfonylurea-type oral hypoglycemics (for example, glipizide). When combined with sulfonamides, these drugs may require a reduction in dosage. TMP/SMZ is contraindicated for nursing mothers, pregnant women in the first semester or near term, infants under 2 months old, patients with folate deficiency (manifested as megaloblastic anemia), and patients with a history of hypersensitivity to sulfonamides and chemically related drugs, including thiazide diuretics, loop diuretics, and sulfonylurea-type oral hypoglycemics. Instruct patients to complete the prescribed course of treatment, even though symptoms may abate before the full course is over.
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
Answer: D Rationale: 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.
Adverse effects of trimethoprim/sulfamethoxazole
Gastrointestinal Nausea and vomiting Rash Hyperkalemia Hypersensitivity reactions (Stevens-Johnson syndrome) Blood dyscrasias Kernicterus Renal damage: Crystalluria
3 adverse effects of trimethoprim
Hematologic effects Hyperkalemia Use in pregnancy and lactation
adverse effects of
Hypersensitivity reactions: Stevens-Johnson syndrome Hematologic effects Kernicterus Renal damage from crystalluria
how does trimethoprim work?
Inhibits dihydrofolate reductase, the enzyme that converts dihydrofolic acid to its active form, tetrahydrofolic acid, thus suppressing bacterial synthesis of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and proteins
how do trimethoprim/sulfamethoxazole work
Suppress bacterial growth by inhibiting tetrahydrofolic acid, a derivative of folic acid or folate
primary use of sulfonamides
UTI
use of silver sulfadiazine and mafenide
Used to suppress bacterial colonization in patients with second- and third-degree burns Local application of mafenide frequently is painful Application of silver sulfadiazine usually is pain free
uses of trimethoprim
acute and uncomplicated UTI
