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.Typically, topical silver sulfadiazine is very well tolerated and doesn’t cause many side effects.

The most common is agranulocytosis. Others include skin necrosis, erythema multiforme, skin discoloration, burning sensation, rashes, and interstitial nephritis.

On the flip side, the list of side effects for oral sulfadiazine, as well as trimethoprim-sulfamethoxazole, is larger. Luckily, the most common ones are mild and include gastrointestinal disturbances like nausea, vomiting, and abdominal pain.

Now, in some cases, trimethoprim-sulfamethoxazole can disrupt the normal intestinal flora, which can allow certain bacteria like Clostridioides difficile to survive and overgrow within the gastrointestinal tract, rarely but potentially leading to Clostridioides difficile infection or CDI for short.

If CDI involves the colon, it is known as pseudomembranous colitis. Other side effects of trimethoprim-sulfamethoxazole include tinnitus, headaches, insomnia, depression, anxiety, or even hallucinations.

More serious side effects include seizures, aseptic meningitis, allergic myocarditis, and hepatotoxicity. They can also affect the kidneys and cause crystalluria as well as electrolyte imbalances, such as hyperkalemia, hyponatremia, while some clients may even develop renal failure or toxic nephrosis.

Trimethoprim-sulfamethoxazole can also cause hematological side effects that could be severe, including hemolytic anemia, thrombocytopenia, and agranulocytosis.

Some clients may also develop a skin rash, dermatitis, urticaria, and photosensitivity. In rare cases, clients may develop serious hypersensitivity reactions, such as Stevens Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, and drug-induced systemic lupus erythematosus, and anaphylactic reactions.As far as contraindications go, these medications shouldn’t be used during pregnancy and breastfeeding, as well as in infants during the first two months of life, since these medications can displace bilirubin from its protein-binding sites in blood, which could lead to hyperbilirubinemia and kernicterus in the newborn.

Precautions should be taken with elderly clients, as well as in those with hepatic or renal disease. Besides this, trimethoprim-sulfamethoxazole is also contraindicated in clients with megaloblastic anemia and a creatinine clearance of less than 15mL/min.

It should be used cautiously in clients with G6PD deficiency, asthma, or hypothyroidism.Regarding interactions, both trimethoprim and sulfonamides are inhibitors of the enzyme cytochrome P450, so they can interfere with the metabolism of certain medications, including warfarin and phenytoin.

They also increase the risk for thrombocytopenia when combined with thiazide diuretics; as well as the hypoglycemic response with sulfonylurea agents; and the bone marrow depressant effects of methotrexate.Now, when a client is diagnosed with a urinary tract infection and is prescribed trimethoprim-sulfamethoxazole, first focus your assessment on their vital signs, noting the presence of fever, and ask them about symptoms like urinary urgency, burning or painful urination, and pelvic or abdominal pain.

Next, review their most recent laboratory test results, including CBC, renal and liver function tests, electrolytes, as well as urinalysis and urine culture and sensitivity.

Finally, confirm a negative pregnancy test for clients of childbearing age. Next, explain to your client how the medication can treat their urinary tract infection.

Instruct them to take this medication twice daily with a full glass of water, and emphasize the importance of completing the entire course of treatment, even if they start to feel better before it’s done.

In addition, remind your clients of childbearing age to use a reliable birth control method during therapy.Then, review some of the side effects that your client could experience.

Let them know that the medication causes photosensitivity, so they should avoid prolonged exposure to sunlight, and when in the sun, prompt them to use sunscreen and protective clothing.

Advise your client to contact their healthcare provider if they notice any skin changes that could indicate a serious hypersensitivity reaction, such as an unusual rash, blistering, or peeling skin; or if they experience symptoms of CDI, such as abdominal cramping, diarrhea, or bloody stool; as well as symptoms of hemolytic anemia, such as fatigue, dark urine, or yellow skin or eyes.

Remind your client to stay well hydrated throughout the treatment, and advise them to drink at least 8 to 10 glasses of water a day, in order to decrease the risk of crystalluria.

Lastly, teach your client about ways to prevent future UTIs, including increasing fluid intake, emptying their bladder regularly and after intercourse; and remind them to wipe their perineal area from front to back after emptying their bladder or bowels.Finally, while your client is taking trimethoprim-sulfamethoxazole, monitor them for the development of side effects, as well as for the desired therapeutic effect of a urinalysis clear of infection and for an absence of UTI symptoms.Alright, as a quick recap… Trimethoprim-sulfamethoxazole is a combined antibiotic medication that works by inhibiting bacterial DNA and RNA synthesis.

It is commonly used to treat acute and simple urinary tract infections or UTIs, as well as acute otitis media, traveler's diarrhea, and shigellosis.

Side effects include photosensitivity, Stevens johnson syndrome, crystalluria, hyperkalemia, blood dyscrasias, and CDI. Nursing considerations related to the administration of trimethoprim-sulfamethoxazole include performing a baseline assessment, teaching the client about side effects and how to manage them, and monitoring the client for side effects and the desired