Antibiotics - Trimethoprim and sulfonamides: Nursing pharmacology

Trimethoprim and sulfonamides are antibiotics that are typically administered in combination as trimethoprim-sulfamethoxazole, or TMP-SMX for short.

TMP-SMX is most commonly used to treat acute and simple urinary tract infections or UTIs, acute otitis media, traveler's diarrhea, and shigellosis. But it’s also effective in treating pneumonia and sinus infections caused by Streptococcus pneumoniae and Haemophilus influenzae.

It’s the first line therapy for the treatment and prevention of Pneumocystis jirovecii infections, which are caused by a yeast-like fungus that can affect immunocompromised people. Finally, it’s effective against Methicillin-Resistant Staphylococcus aureus, or MRSA.

Trimethoprim-sulfamethoxazole is most often given orally, and for serious infections and Pneumocystis jirovecii pneumonia, it can be administered intravenously.

Now, sulfonamides can also be used alone as sulfadiazine orally to treat infection by Toxoplasma gondii, or as silver sulfadiazine, which is administered topically in clients with second and third-degree burns to help prevent and treat wound sepsis.

Now, once administered, these medications act to inhibit the synthesis of folate, also known as folic acid or vitamin B9, which is necessary for the synthesis of DNA and RNA. As a result, they interfere with bacterial DNA and RNA synthesis, which ultimately kills the bacteria.