The sulfonamides, or sulfa drugs, are drugs that inhibit folic acid synthesis. Sulfonamides include sulfadiazine (generic), sulfisoxazole (Gantrisin), sulfasalazine (Azulfidine), and cotrimoxazole (Septra, Bactrim).
Folic acid is necessary for the synthesis of purines and pyrimidines, which are precursors of RNA and DNA. For cells to grow and reproduce, they require folic acid. Humans cannot synthesize folic acid and depend on the folate in their diet to obtain this essential substance. Bacteria are impermeable to folic acid and must synthesize it inside the cell. The sulfonamides competitively block para-aminobenzoic acid (PABA) to prevent the synthesis of folic acid in susceptible bacteria that synthesize their own folates for the production of RNA and DNA. This includes gram-negative and gram-positive bacteria such as Chlamydia trachomatis and Nocardia and some strains of H. influenzae, E. coli, and P. mirabilis.
Because of the emergence of resistant bacterial strains and the development of newer antibiotics, the sulfa drugs are no longer used much. However, they remain an inexpensive and effective treatment for UTIs and trachoma, especially in developing countries and when cost is an issue. These drugs are used to treat trachoma (a leading cause of blindness), nocardiosis (which causes pneumonias, as well as brain abscesses and inflammation), UTIs, and sexually transmitted diseases. Sulfisoxazole has an off-label use of prophylaxis for recurrent otitis media.
The sulfonamides are teratogenic; they are distributed into breast milk. These drugs, given orally, are absorbed from the GI tract, metabolized in the liver, and excreted in the urine. The time to peak level and the half-life of the individual drug vary.
Sulfadiazine is an oral agent slowly absorbed from the GI tract, reaching peak levels in 3 to 6 hours.
磺胺嘧啶是一种口服药，经胃肠道慢慢吸收。3-6后小时达到峰值。
Sulfisoxazole is rapidly absorbed from the GI tract, reaching peak levels in 2 hours. After being metabolized in the liver, it is excreted in the urine with a half-life of 4.5 to 7.8 hours.
Sulfasalazine is a sulfapyridine that is carried by aminosalicylic acids (aspirin), which release the aminosalicylic acid in the colon. In a delayed-release form, this sulfa drug is also used to treat rheumatoid arthritis that does not respond to other treatments. It is rapidly absorbed from the GI tract, reaching peak levels in 2 to 6 hours. After being metabolized in the liver, it is excreted in the urine with a half-life of 5 to 10 hours.
Cotrimoxazole is a combination drug that contains sulfamethoxazole and trimethoprim, another antibacterial drug. It is rapidly absorbed from the GI tract, reaching peak levels in 2 hours. After being metabolized in the liver, it is excreted in the urine with a half-life of 7 to 12 hours.
sulfonamide – n. 磺胺类药
sulfa – n. 磺胺
sulfadiazine – n. 磺胺嘧啶
sulfisoxazole – n. 磺胺异噁唑 Gantrisin – n.【奥】甘特里辛
sulfasalazine – n. 柳氮磺吡啶 Azulfidine – n. 【奥】阿佐吡啶
cotrimoxazole – n. 磺胺甲基异噁唑 Septra – n. 复方新诺明 Bactrim – n. 新诺明
pyrimidine – n. 嘧啶
folate – n. 叶酸 para-aminobenzoic acid – 对氨基苯甲酸
PABA = para-aminobenzoic acid chlamydia trachomatis – 沙眼衣原体 Nocardia – n. 诺卡尔菌
nocardiosis – n. 诺卡菌病
teratogenic – a. 产生畸形的，畸形形成的
sulfapyridine – n. 磺胺吡啶
aminosalicylic acids – n. 氨基水杨酸类
Test 1. A nurse teaches a patient about sulfonamides. Which statement by the patient indicates a need for further teaching?
A. "I need to drink extra fluids while taking this medication."
B. "I need to use sunscreen when taking this drug."
C. "I should call my provider if I develop a rash while taking this drug."
D. "I should stop taking this drug when my symptoms are gone."
2. A patient taking a sulfonamide is breast-feeding an infant. Which complication in the infant would the nurse associate with kernicterus?
A. Hemolytic anemia
B. Neurologic deficits
C. Hepatocellular failure
D. Ophthalmic infection
本期ISPN Review答案： 1. D. "I should stop taking this drug when my symptoms are gone."
Patients should always be advised to complete the prescribed course of the antibiotic even when symptoms subside. Patients should also understand the need to drink 8 to 10 glasses of water a day, to use sunscreen, and to notify the provider if they develop a rash.
2. B. Neurologic deficits
Kernicterus is a disorder in newborns caused by deposition of bilirubin in the brain, which leads to severe neurologic deficits and death. Sulfonamides promote kernicterus by displacing protein-bound bilirubin from the proteins, leaving newly freed bilirubin access to brain sites. Sulfonamides are not administered to infants under 2 years old, nor are they given to pregnant patients near term or nursing mothers. Hemolytic anemia, hepatocellular failure, and ophthalmic infection are not associated sulfonamide effects in infants.
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