12.9 Sulfonamides
Sulfonamides or ‘sulfa’ antibiotics are one of the oldest broad-spectrum antimicrobial agents that work by competitively inhibiting bacterial metabolic enzymes needed for bacterial function. There are many drugs in this class, including Sulfamethizole and Sulfamethoxazole.
Indications for Use
Sulfonamides are used to treat urinary tract infections, otitis media, acute exacerbations of chronic bronchitis, and travelers’ diarrhea.
Mechanism of Action
This mechanism of action provides bacteriostatic inhibition of growth against a wide spectrum of gram-positive and gram-negative pathogens.
Nursing Considerations
Administration: oral and IV. Oral dosing take with food and lots of water.
Sulfonamides are safe for use in pregnancy and with pediatric clients. Dosing should be altered for any client with renal insufficiency.
Sulfamethoxazole is often combined with trimethoprim, which is an antifolate antibiotic. Trimethoprim/sulfamethoxazole combination is done to avoid resistance and for synergistic effects of inhibiting folic acid in bacteria at two different points.
Allergy alert: Allergic reactions to sulfonamide medications are common and, therefore, clients should be monitored carefully for adverse effects including delayed hypersensitivity reactions. There is also a cross sensitivity to loop diuretics and thiazide diuretics so ensure to check with the prescriber before giving the first dose.
Drug Interactions
There is numerous drug interactions so ensure to complete a thorough medication profile. Some interactions with this med are:
- Phenytoin: may increase phenytoin levels so closely monitor phenytoin levels.
- Warfarin: may increase bleeding so closely monitor INR and dose should be adjusted.
- Oral anti-diabetic medications (Tobutamide, tolazamide, glyburide, glipizide, chlorpropamide, metformin, pioglitazone – ↑ risk of hypoglycemia).
- Cyclosporines can ↑ risk of nephrotoxicity.
Adverse/Side Effects
Common side effects include GI effects of nausea, diarrhea, anorexia and abdominal discomfort. May also experience headache and insomnia.
Increased risk of crystalluria that can cause kidney stones or decreased kidney function; therefore, clients should increase their water intake while taking these medications.
Other adverse effects include:
- Hyperkalemia may occur so monitor serum electrolytes in susceptible clients.
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Kernicterus in neonates
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Photosensitivity: advise client to use sunscreen or to stay out of the sun.
Client Teaching
- The client should receive education to complete the full prescribed dose of medications and take measures to not skip doses. If a dose is missed, the client should take the missed dose as soon as possible unless it is near the next dosing time.
- Can cause increased photosensitivity, and clients should be educated to use sunscreen and protective clothing with sun exposure.
- Report any rash, sore throat, fever, or mouth sores that might occur.
- Unusual bleeding or bruising should also be reported to the provider.
- Report any fever and diarrhea especially if diarrhea contains blood or pus. Contact prescriber for treatment.
- If clients are receiving prolonged therapy, they may require platelet count monitoring.[1]
Sulfonamides Medication Card
Now let’s take a closer look at the medication card for trimethoprim-sulfamethoxazole (Daily Med, 2019). Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication.
To help with comparing the medications and to learn important considerations for each medication, refer to the: Chapter 12 Antimicrobials Medication Cards
Medication Card: Sulfonamides
Prototypes: Trimethoprim/Sulfamethoxazole, often referred to as “sulfa drugs”
Example: Septra, Co-trimoxazole (Bactrim)
Mechanism: Bacteriostatic inhibition of growth against a wide spectrum of gram-positive and gram-negative pathogen.
Indications: Broad spectrum, Gram + and – organisms. Very effective against UTIs. Also used for respiratory tract infections and general prophylaxis against infection. Not effective against infections with ‘pus’. Not widely used due to resistance.
Administration
- oral or IV
- PO: 1-4hr (Peak effect). Take with lots of water to avoid crystalluria.
- IV: immediate onset
Side Effects
- GI: N/V, Diarrhea, anorexia, abdo pain
- CNS: Convulsions, Headache
- GU: Crystalluria
- Hyperkalemia
- anemia
- photosensitivity
- folate deficiency
- Serious adverse effects include Stevens-Johnson syndrome, pancreatitis, bone marrow depression, toxic nephrosis
- “sulfa allergy” – starts with fever and rash
Contraindications
- Sulfonylureas. sulfonamine, or thiazide diuretics – increase risk of hypoglycemia
- Hypersensitivity
- Cyclosporin- ↑ Risk of nephrotoxicity
- Pregnancy/ lactating
- Peds: do not give if under 2 years of age. Caution with older adult
- Phenytoin
- Warfarin
- Hx kidney stones or renal disease
Nursing Considerations
- Take with trimethoprim for synergistic effects
- Monitor skin (rash), bowels (diarrhea)
- *must take with LOTS of water. Stay hydrated.
Clinical Reasoning and Decision-Making Activity
Using the above information, consider the following clinical scenario question:
A nurse is caring for an elderly diabetic client who has been prescribed trimethoprim-sulfamethoxazole for a urinary tract infection.
a. What nursing interventions will be implemented prior to medication administration?
b. The client has some questions about the instructions with taking this med. Provide a rationale for each question:
-Why do I need to take a full glass of water when I take this med?
– I often experience diarrhea already. How do I know if it is related to the drug?
– Am I able to go outside if I have to avoid the sun?
Note: Answers to the Clinical Reasoning Activities and Critical Thinking questions can be found in the Chapter 12: Antimicrobial Medications answer key – Fundamentals of Nursing Pharmacology – 2nd Canadian Edition section at the end of the book.
References
- uCentral from Unbound Medicine. https://www.unboundmedicine.com/ucentral ↵
- Daily Med, https://dailymed.nlm.nih.gov/dailymed/index.cfm, used for hyperlinked medications in this module. Retrieved June 27, 2019 ↵
