sulfonamide

Definition

Sulfonamides are medicines that prevent the growth of bacteria in the body.

Description

Sulfonamides, also called sulfa medicines, are available only with a physician's prescription. They are sold in tablet and liquid forms. Some commonly used sulfonamides are sulfisoxazole (Gantrisin) and the combination drug sulfamethoxazole and trimethoprim (Bactrim, Cotrim).

— Nancy Ross-Flanigan

1. Any of a group of organic sulfur compounds containing the radical SO₂NH₂ and including the sulfa drugs.
2. See sulfa drug.

One of the group of organosulfur compounds, RSO₂NH₂. Many sulfonamides, which are the amides of sulfonic acids, have the marked ability to halt the growth of bacteria. The therapeutic drugs of this group are known as sulfa drugs. See also Organosulfur compound.

The antibacterial spectrum of sulfonamides comprises a wide variety of gram-positive and gram-negative bacteria, including staphylococci, streptococci, meningococci, and gonococci, as well as the gangrene, tetanus, coli, dysentery, and cholera bacilli. They have only slight activity against Mycobacterium tuberculosis, while certain closely related sulfones are quite active against M. leprae. The use of sulfonmethoxine has proved to be effective in the treatment of chloroquine-resistant malaria. The relative potency of sulfonamides against the different microorganisms varies, and their action is bacteriostatic rather than bactericidal.

The antibacterial effect, both in patients and in test tube cultures, is antagonized by p-amino­benzoic acid (PABA) and PABA-containing natural or synthetic products, such as folic acid and procaine. Accordingly, the mode of action of sulfonamides is considered to be an antimetabolite activity, dependent upon the inhibition of enzyme systems involving the essential PABA.

Bacterial resistance has developed to all known sulfonamides, and many sulfonamide-resistant strains are encountered among the gram-positive and gram-negative bacteria. The emergence of resistance to sulfonamides, however, seems less rapid and less widespread than resistance to most antibiotics.

Sulfonamides are used today mostly as auxiliary drugs or in combination with antibiotics. In certain infectious diseases, however (for instance, in meningococcal infections and most infections of the urinary tract), sulfonamides deserve preference over antibiotics.

A derivative of sulfanilamide that is effective against microorganisms.

Definition

Sulfonamides, sometimes called sulfa drugs, are medicines that prevent the growth of bacteria in the body. The sulfonamides have largely been replaced by the antibiotics which generally are safer and more effective.

Description

Sulfonamides are used to treat many kinds of infections caused by bacteria and certain other microorganisms. Physicians may prescribe these drugs to treat urinary tract infections, ear infections, frequent or long lasting bronchitis, bacterial meningitis, certain eye infections, Pneumocystis cariniipneumonia, traveler's diarrhea, and a number of other kinds of infections. These drugs will not work for colds, flu, and other infections caused by viruses.

Description

Although there were many sulfonamides, relatively few are in use as of 2004:

• Sulfisoxazole (Gantrisin) is used to treat urinary tract infections. In combination with erythromycin, sulfisoxazole may be used to treat ear infections in children.
• Trimethoprim/sulfamethoxazole (Bactrim, Septra) is a combination of two sulfonamides used together. The combination is more effective than giving either drug alone in a larger dose. The combination is commonly used to treat urinary tract infections and other infections that cannot be treated with antibiotics.
• Sulfadiazine may be used to protect people with rheumatic fever from infections. It is used to treat toxoplasmosis. An ointment containing silver sulfadiazine is widely used for treatment of burns.
• Sulfasalazine (Azulfadine) is used to treat infections of the colon and intestine.

General Use

The most common use for sulfonamides in adults is treatment of urinary tract infections. In children, sulfonamides have more limited use. Sulfisoxazole may be used for prophylaxis of ear infections and prevention of meningococcal infections. Sulfasakazube is used to treat children over the age of two years with ulcerative colitis.

Precautions

Sulfonamides should never be used in infants under the age of two months. They should also be used with extreme care in patients with liver problems, kidney problems, and some types of anemia.

Side Effects

Although such side effects are rare, some people have severe and life-threatening reactions to sulfonamides. These include sudden, severe liver damage; serious blood problems; breakdown of the outer layer of the skin; and a condition called Stevens-Johnson syndrome, in which people get blisters around the mouth, eyes, or anus. People should call a physician immediately if any of the following signs of a dangerous reaction occur:

• skin rash or reddish or purplish spots on the skin
• other skin problems, such as blistering or peeling
• fever
• sore throat
• cough
• shortness of breath
• joint pain
• pale skin
• yellow skin or eyes

This medicine may cause dizziness. Sulfonamides may also cause blood problems that can interfere with healing and lead to additional infections. This medicine may increase sensitivity to sunlight. Even brief exposure to sun can cause severe sunburn or rash. While being treated with this medicine, people should avoid being in direct sunlight. Very rarely, systemic sulfonamides may even cause kidney stones.

The most serious adverse effects of sulfonamides cannot be predicted. Some steps can minimize some of the less severe adverse effects. Because sulfonamides are not very soluble, they should always be taken with a full glass of water. Moreover, sulfonamides increase sensitivity to sunlight and increase the risk of sunburn. People taking sulfonamides by mouth should avoid direct sunlight and stay covered up. They should not rely on sunscreens. This risk does not apply, however, to people using sulfonamide eye or ear drops. Oral sulfonamides should always be taken in evenly spaced doses to maintain a steady blood level throughout the day.

Interactions

Sulfonamides may interact with a large number of other medicines. When interaction occurs, the effects of one or both of the drugs may change or the risk of side effects may be greater. People who take sulfonamides should let their physician know all other medicines they are taking. Among the drugs that may interact with sulfonamides are:

• acetaminophen (Tylenol)
• medicine for overactive thyroid
• other medicines used to treat infections
• birth control pills
• medicines for diabetes, such as glyburide (Micronase)
• anticoagulants, such as warfarin (Coumadin)
• amantadine (Symmetrel)
• water pills (diuretics) such as hydrochlorothiazide (HCTZ, HydroDIURIL)
• the anticancer drug methotrexate (Rheumatrex)
• antiseizure medicines such as valproic acid (Depakote, Depakene)

The list above does not include every drug that may interact with sulfonamides but is limited to drugs that might be used in treatment of children and adolescents. Parents should be sure to check with a physician or pharmacist before combining sulfonamides with any other prescription or nonprescription (over-the-counter) medicine.

Parental Concerns

Parents giving their children eye or ear drops should be sure they know the proper way to administer these drops. Parents should review the technique with a physician or nurse to be sure the medication is given properly. If children are taking sulfonamides by mouth, parents should be sure that the children are drinking a full glass of water with each dose. Because some of the adverse effects of sulfonamides may be very serious, parents should report any suspicious symptoms to their physician promptly.

See also Cystitis; Penicillins; Tetracyclines.

Resources

Books

Beers Mark H., and Robert Berkow, eds. The Merck Manual, 2nd ed. home edition. West Point, PA: Merck & Co., 2004.

Marx, John A. Rosen's Emergency Medicine: Concepts andClinical Practice, 5th ed. St. Louis, MO: Mosby & Co, 2002.

Mcevoy, Gerald K., et al. AHFS Drug Information 2004. Bethesda, MD: American Society of Healthsystems Pharmacists, 2004.

Siberry, George K., and Robert Iannone, eds. The Harriet Lane Handbook, 15th ed. Philadelphia: Mosby Publishing, 2000.

Periodicals

American Academy of Pediatrics, Committee on Quality Improvement, Subcommittee on Urinary Tract Infection. "Practice parameter: the diagnosis, treatment, and evaluation of the initial urinary tract infection in febrile infants and young children." Journal of Pediatrics 105, no. 2 (February 2000): 463–464.

Halasa, Natasha B., et al. "Differences in antibiotic prescribing patterns for children younger than five years in the three major outpatient settings." Journal of Pediatrics 144, no. 2 (February 2004): 200–205.

Witman, P. M. "Pediatric oral medicine." Dermatolgic Clinics of North America 21, no. 1 (January 2003): 157–170.

Organizations

American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007–1098. Web site: www.aap.org.

Web Sites

"Med Chem Group 7—Antibiotics." University of Michigan,College of Pharmacy. Available online at (accessed September 29, 2004).

"Sulfonamides (Ophthalmic)." MedlinePlus. Available online at www.nlm.nih.gov/medlineplus/druginfo/uspdi/202539.html (accessed September 29, 2004).

[Article by: Nancy Ross-Flanigan Samuel Uretsky, PharmD]

1. any compound containing the −SO₂NH₂ group.
2. any of a group of drugs that are derivatives of sulfanilamide, which competitively inhibit folic acid synthesis in microorganisms, and are bacteriostatic against gram-positive cocci (streptococci and pneumococci), gram-negative cocci (meningococci and gonococci), gram-negative bacilli (Escherichia coli and shigellae), and a wide variety of other bacteria. Sulfonamides have been supplanted by more effective and less toxic antibiotics in most uses. Called also sulfa drugs.