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Drugs, Supplies and Delivery
Co-trimoxazole
Moxifloxacin is a potent fluoroquinolone for respiratory, skin, and intra-abdominal infections. While effective, its use requires vigilance for QT prolongation, tendon injury, and drug interactions. Adherence to guidelines from the BNF, Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology ensures safe and effective therapy.
Co-trimoxazole is a fixed-dose combination of two antimicrobial agents: sulfamethoxazole (a sulfonamide) and trimethoprim (a diaminopyrimidine). The combination works synergistically to inhibit sequential steps in bacterial folate synthesis:
- Sulfamethoxazole: Inhibits dihydropteroate synthase, blocking the conversion of PABA to dihydrofolic acid.
- Trimethoprim: Inhibits dihydrofolate reductase, preventing the conversion of dihydrofolic acid to tetrahydrofolic acid.
This dual action disrupts DNA, RNA, and protein synthesis, leading to bacteriostatic effects.
Co-trimoxazole is effective against:
- Gram-positive bacteria: Streptococcus pneumoniae, Staphylococcus aureus.
- Gram-negative bacteria: Escherichia coli, Klebsiella, Proteus, Salmonella, Shigella.
- Opportunistic pathogens: Pneumocystis jirovecii, Toxoplasma gondii.
Co-trimoxazole is indicated for:
- Respiratory Infections:
- Acute exacerbations of chronic bronchitis.
- Community-acquired pneumonia (especially Pneumocystis jirovecii pneumonia in immunocompromised patients).
- Urinary Tract Infections (UTIs):
- Acute uncomplicated cystitis.
- Recurrent UTIs.
- Gastrointestinal Infections:
- Traveler’s diarrhea (E. coli, Shigella).
- Typhoid fever (Salmonella typhi).
- Opportunistic Infections:
- Pneumocystis pneumonia (PCP): Prophylaxis and treatment in HIV/AIDS patients.
- Toxoplasmosis: Prophylaxis in immunocompromised patients.
- Skin and Soft Tissue Infections:
- Cellulitis, wound infections.
Adults:
- Standard Dose: 960 mg (sulfamethoxazole 800 mg + trimethoprim 160 mg) twice daily.
- PCP Treatment: 120 mg/kg/day in divided doses for 14–21 days.
- PCP Prophylaxis: 960 mg once daily or 3 times weekly.
Children:
- Standard Dose: 24 mg/kg/day (sulfamethoxazole 20 mg/kg + trimethoprim 4 mg/kg) in divided doses.
- PCP Prophylaxis: 450 mg/m² twice daily on 3 consecutive days per week.
Special Populations:
- Renal Impairment: Adjust dose based on creatinine clearance (CrCl):
- CrCl 15–30 mL/min: Reduce dose by 50%.
- CrCl <15 mL/min: Avoid unless essential.
Hepatic Impairment: Use with caution; monitor LFTs.
- Common: Nausea, vomiting, diarrhea, rash, headache.
- Serious:
- Hematologic Effects: Megaloblastic anemia, leukopenia, thrombocytopenia.
- Hypersensitivity Reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis.
- Renal Toxicity: Crystalluria, interstitial nephritis.
- Hyperkalemia: Due to trimethoprim’s potassium-sparing effect.
- Hepatotoxicity: Elevated LFTs, hepatitis.
- Hypersensitivity: Avoid in patients with sulfonamide allergy.
- Pregnancy: Category C (avoid in third trimester due to risk of kernicterus).
- Lactation: Excreted in breast milk; avoid breastfeeding.
- Renal/Hepatic Impairment: Monitor renal function and LFTs.
- Folate Deficiency: Supplement with folic acid in high-risk patients (e.g., elderly, malnourished).
Co-trimoxazole interacts with drugs metabolized by CYP450 enzymes and those affecting folate metabolism:
- Warfarin: Increased INR (monitor closely).
- Phenytoin: Increased levels (risk of toxicity).
- Methotrexate: Increased toxicity (avoid combination).
- ACE Inhibitors: Increased risk of hyperkalemia.
- Cyclosporine: Increased nephrotoxicity.
- Oral Hypoglycemics: Enhanced hypoglycemic effect.
- Generic: Co-trimoxazole (sulfamethoxazole + trimethoprim).
Brand Names: Bactrim, Septra, Septrin
