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# Septran (Co-Trimoxazole)
## Overview
Septran is a combination antibiotic containing sulfamethoxazole and trimethoprim in a fixed ratio of 5:1. It is bactericidal.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PJP) prophylaxis and treatment
* Acute exacerbations of chronic bronchitis
* Shigellosis
* Traveler's diarrhea (ETEC)
## Adult Dosing
* **Urinary Tract Infections:** 160 mg TMP/800 mg SMX (1 double-strength tablet) every 12 hours for 3-7 days.
* **Pneumocystis jirovecii pneumonia (treatment):** 15 mg/kg/day TMP (based on TMP component) divided into 3-4 doses. Typically 160 mg TMP/800 mg SMX every 6-8 hours for 14-21 days.
* **Pneumocystis jirovecii pneumonia (prophylaxis):** 160 mg TMP/800 mg SMX (1 double-strength tablet) once daily. Alternative: 160 mg TMP/800 mg SMX three times a week.
* **Acute exacerbations of chronic bronchitis:** 160 mg TMP/800 mg SMX every 12 hours for 5-7 days.
* **Shigellosis:** 160 mg TMP/800 mg SMX every 12 hours for 5 days.
* **Traveler's diarrhea:** 160 mg TMP/800 mg SMX every 12 hours for 3 days.
Maximum daily dose for adults is typically 4 double-strength tablets (320 mg TMP/1600 mg SMX).
## Pediatric Dosing
Dosing is based on the trimethoprim component.
* **Urinary Tract Infections (greater than 2 months):** 8 mg/kg/day TMP (based on TMP component) divided into two doses. Typically 40 mg SMX/8 mg TMP per 5 mL suspension or 1 DS tablet for every 30-40 pounds. Administer every 12 hours for 7-14 days.
* **Pneumocystis jirovecii pneumonia (treatment, greater than 2 months):** 15 mg/kg/day TMP (based on TMP component) divided into 3-4 doses for 14-21 days.
* **Pneumocystis jirovecii pneumonia (prophylaxis, greater than 2 months):** 5 mg/kg/day TMP (based on TMP component) divided into two doses, given twice daily for 3 days a week or once daily. (Total daily dose not to exceed 320 mg TMP/1600 mg SMX).
*Note: For pediatric UTIs and PJP prophylaxis, specific protocols may vary. Refer to local guidelines.*
## Dose Adjustments
* **Renal Impairment (Adults):**
* CrCl > 30 mL/min: No adjustment needed.
* CrCl 15-30 mL/min: Half the standard dose.
* CrCl < 15 mL/min: Contraindicated.
* **Hepatic Impairment:** Use with caution.
## Contraindications
* Known hypersensitivity to trimethoprim, sulfonamides, or any component of the formulation.
* Severe renal insufficiency (CrCl < 15 mL/min).
* Documented megaloblastic anemia due to folate deficiency.
* Premature infants and full-term infants during the first 2 months of life.
* Patients with a history of drug-induced thrombocytopenia with either agent.
* Breastfeeding mothers of premature infants or infants younger than 2 months.
## Adverse Effects
Common: Nausea, vomiting, rash, diarrhea.
Serious: Stevens-Johnson syndrome, toxic epidermal necrolysis, severe skin reactions, hepatic toxicity, renal toxicity, hyperkalemia, bone marrow suppression (anemia, leukopenia, thrombocytopenia), photosensitivity, C. difficile-associated diarrhea.
## Key Drug Interactions
* **Warfarin:** Increased INR. Monitor INR closely.
* **Methotrexate:** Increased methotrexate levels and potential toxicity.
* **Potassium-sparing diuretics (e.g., spironolactone, amiloride):** Increased risk of hyperkalemia.
* **ACE inhibitors and ARBs:** Increased risk of hyperkalemia.
* **Cyclosporine:** Increased cyclosporine levels.
* **Digoxin:** Increased digoxin levels.
* **Tricyclic Antidepressants:** Reduced efficacy of antidepressants.
* **Dapsone:** Increased levels of both drugs.
* **Potassium Supplements:** Increased risk of hyperkalemia.
* **Diuretics (e.g., thiazides):** Increased risk of thrombocytopenia in elderly patients.
## Monitoring
* Complete blood count (CBC) with differential and platelet count, especially for prolonged therapy or in elderly patients.
* Renal function (BUN, creatinine).
* Liver function tests (LFTs).
* Electrolytes (especially potassium).
* For patients on warfarin, monitor INR.
* Monitor for signs and symptoms of hypersensitivity reactions and C. difficile.
## Clinical Pearls
* Co-trimoxazole should be taken with a full glass of water.
* Encourage increased fluid intake to prevent crystalluria.
* Photosensitivity is common; advise patients to use sun protection.
* Educate patients on signs and symptoms of serious allergic reactions and to seek immediate medical attention.
* TMP/SMX can interfere with certain laboratory tests (e.g., serum creatinine assay, causing falsely elevated levels).
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*Disclaimer: This information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional to ensure the appropriateness of this medication for your specific condition and to review the most current prescribing information.*
