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# Septran (Trimethoprim/Sulfamethoxazole)
## Overview
Septran is a combination antibiotic consisting of trimethoprim and sulfamethoxazole, which work synergistically to inhibit bacterial folic acid synthesis. It is available in various formulations, including oral tablets, oral suspension, and intravenous injection.
## Primary Indications
* Urinary tract infections (UTIs)
* Pneumocystis jirovecii pneumonia (PCP) prophylaxis and treatment
* Bacterial respiratory tract infections (e.g., acute exacerbations of chronic bronchitis)
* Shigellosis
* Acute otitis media
* Traveler's diarrhea
## Adult Dosing
Dosing is typically based on the trimethoprim component, with a standard ratio of 1:5 (trimethoprim:sulfamethoxazole).
* **Urinary Tract Infections:** 160 mg trimethoprim / 800 mg sulfamethoxazole every 12 hours for 3-7 days (standard strength tablet).
* **Pneumocystis jirovecii Pneumonia (Treatment):** 15-20 mg/kg/day (as trimethoprim component) divided every 6-8 hours for 14-21 days.
* **Pneumocystis jirovecii Pneumonia (Prophylaxis):** 160 mg trimethoprim / 800 mg sulfamethoxazole orally once daily, or 160 mg trimethoprim / 800 mg sulfamethoxazole orally three times a week.
* **Other Infections:** Dosing varies based on severity and organism. Common regimens include 160 mg trimethoprim / 800 mg sulfamethoxazole every 12 hours. Severe infections may warrant higher doses.
## Pediatric Dosing
Dosing is based on the trimethoprim component and the child's weight.
* **Urinary Tract Infections & Shigellosis:** 8 mg/kg/day (as trimethoprim component) divided every 12 hours for 5-10 days (UTIs) or 5 days (shigellosis).
* **Pneumocystis jirovecii Pneumonia (Treatment):** 15-20 mg/kg/day (as trimethoprim component) divided every 6-8 hours for 14-21 days.
* **Pneumocystis jirovecii Pneumonia (Prophylaxis):** 5 mg/kg/day (as trimethoprim component) divided every 12 hours, administered twice daily on 3 consecutive days per week.
## Dose Adjustments
* **Renal Impairment:** Dosage adjustment is necessary for moderate to severe renal impairment (CrCl < 30 mL/min). Consult prescribing information for specific guidance.
* **Hepatic Impairment:** Caution is advised; dose adjustments may be needed.
## Contraindications
* Known hypersensitivity to trimethoprim, sulfamethoxazole, or sulfonamides.
* Infants less than 2 months of age (due to risk of kernicterus).
* Patients with megaloblastic anemia due to folate deficiency.
* Severe renal insufficiency or hepatic insufficiency when plasma concentrations cannot be monitored.
## Adverse Effects
Common adverse effects include rash, pruritus, nausea, vomiting, and diarrhea. Serious adverse effects can include:
* Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN)
* Hematologic abnormalities (e.g., leukopenia, thrombocytopenia, anemia)
* Hyperkalemia
* Hepatitis
* Renal impairment
* Photosensitivity
## Key Drug Interactions
* **Warfarin:** Increased INR; requires close monitoring and potential warfarin dose adjustment.
* **Methotrexate:** Increased methotrexate levels; risk of toxicity.
* **Potassium-sparing diuretics:** Increased risk of hyperkalemia.
* **ACE inhibitors/ARBs:** Increased risk of hyperkalemia.
* **Dofetilide:** Increased risk of arrhythmias.
* **Digoxin:** May increase digoxin levels.
## Monitoring
* **Renal function:** Baseline and periodic monitoring.
* **Electrolytes:** Particularly potassium, especially in patients with renal impairment or those taking other medications that affect potassium.
* **Complete blood count (CBC):** Baseline and periodic monitoring for hematologic toxicity.
* **Liver function tests:** Periodic monitoring, especially with prolonged therapy.
* **Therapeutic drug monitoring:** May be indicated in certain situations, such as severe infections or suspected toxicity.
## Clinical Pearls
* Advise patients to drink plenty of fluids to prevent crystalluria.
* Sulfonamides can cause photosensitivity; recommend sun protection.
* Discontinue if rash develops, as it may indicate a serious hypersensitivity reaction.
* Trimethoprim can cause hyperkalemia; monitor potassium levels, especially in at-risk patients.
* Not recommended for empiric treatment of Group A Streptococcus pharyngitis due to suboptimal eradication rates.
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*Disclaimer: This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines before making clinical decisions. Dosing and indications may vary based on local protocols and specific patient factors.*
