Bactrim is a combination antibiotic medication containing sulfamethoxazole and trimethoprim. It operates through a sequential blockade of bacterial folate synthesis, effectively treating a wide spectrum of susceptible bacterial strains. This synergistic mechanism enhances bactericidal activity and reduces the potential for resistance development compared to single-agent therapies. It is a trusted choice for healthcare providers in both community and hospital settings for specific indicated infections.

Features

• Contains a fixed 5:1 ratio of sulfamethoxazole to trimethoprim
• Available in oral tablet (single strength and double strength) and oral suspension formulations
• Exhibits broad-spectrum activity against Gram-positive and Gram-negative bacteria
• Bactericidal action through inhibition of two consecutive steps in the folate biosynthesis pathway
• Standardized dosing allows for predictable pharmacokinetics

Benefits

• Provides synergistic antibacterial activity, often more effective than its individual components alone
• Effective against a range of common and opportunistic infections, including those resistant to other antibiotics
• Convenient twice-daily dosing regimen supports patient adherence to treatment
• Well-established efficacy and safety profile based on decades of clinical use
• Used for both treatment and prophylaxis of specific infections, such as Pneumocystis jirovecii pneumonia (PCP)

Common use

Bactrim is indicated for the treatment of various bacterial infections caused by susceptible organisms. Its primary uses include urinary tract infections (acute, recurrent, or chronic), acute exacerbations of chronic bronchitis in adults, acute otitis media in children, and traveler’s diarrhea. It is also a first-line agent for the treatment and prophylaxis of Pneumocystis jirovecii pneumonia (PCP), particularly in immunocompromised patients, such as those with HIV/AIDS. Furthermore, it is used in the management of shigellosis and for prophylaxis in individuals with recurrent urinary tract infections.

Dosage and direction

Dosage must be individualized based on the type and severity of infection, renal function, and patient factors. For most infections in adults and children over 2 months, the typical dosage is based on the trimethoprim component: 8-10 mg/kg/day, administered in two divided doses every 12 hours. For PCP treatment, a higher dose of 15-20 mg/kg/day (trimethoprim component) is used. For prophylaxis of PCP, the dose is typically 5 mg/kg/day (trimethoprim) given once daily or in divided doses. In patients with renal impairment (CrCl < 30 mL/min), dosage reduction is necessary. Tablets should be taken with a full glass of water, and the oral suspension must be shaken well before each use.

Precautions

Use with caution in patients with renal or hepatic impairment, severe allergies, or bronchial asthma. Maintain adequate hydration to prevent crystalluria and stone formation. Periodic CBC is recommended during prolonged therapy due to the risk of hematologic toxicity. Monitor for signs of superinfection or fungal overgrowth. Use with caution in the elderly, as they may be more susceptible to adverse effects, particularly hyperkalemia and thrombocytopenia. Patients with G6PD deficiency are at increased risk of hemolytic anemia. May cause photosensitivity; advise patients to use sun protection.

Contraindications

Hypersensitivity to sulfamethoxazole, trimethoprim, or any sulfonamide-derived drugs. Documented history of drug-induced immune thrombocytopenia from trimethoprim or sulfonamides. Marked renal or hepatic impairment where the risks outweigh benefits. Pregnancy at term and during the nursing period, due to the risk of kernicterus in the newborn. Infants less than 2 months of age. Concomitant use with dofetilide.

Possible side effect

Common side effects include nausea, vomiting, loss of appetite, and skin rash. Less frequently, patients may experience headache, dizziness, or insomnia. Serious but rare adverse effects include Stevens-Johnson syndrome, toxic epidermal necrolysis, agranulocytosis, aplastic anemia, hepatotoxicity, hyperkalemia (particularly in the elderly or those on ACE inhibitors), and aseptic meningitis. Clostridium difficile-associated diarrhea has been reported. Any sign of blood dyscrasia (e.g., sore throat, fever, pallor, purpura) requires immediate medical attention.

Drug interaction

Bactrim may potentiate the effects of warfarin, phenytoin, and sulfonylureas, necessitating close monitoring. It can increase the levels and toxicity of methotrexate. Concurrent use with ACE inhibitors or ARBs may increase the risk of hyperkalemia. It may reduce the efficacy of cyclosporine. Concomitant use with thiazide diuretics in the elderly can increase the risk of thrombocytopenia. Bactrim can inhibit the metabolism of tricyclic antidepressants. It may decrease the efficacy of oral contraceptives; advise alternative contraception. Avoid concomitant use with dofetilide due to increased risk of fatal arrhythmias.

Missed dose

If a dose is missed, it should be taken as soon as remembered. However, if it is almost time for the next scheduled dose, the missed dose should be skipped. Doubling the dose to make up for a missed one is not recommended, as it may increase the risk of adverse effects. Patients should be instructed to maintain the regular dosing schedule and not to discontinue therapy prematurely even if symptoms improve.

Overdose

Symptoms of overdose may include nausea, vomiting, dizziness, headache, mental status changes, bone marrow depression, and crystalluria. In acute overdose, emesis or gastric lavage may be considered if performed early. Maintain adequate hydration to promote urinary excretion and prevent crystall formation. Monitor CBC and electrolytes. Hemodialysis is moderately effective in removing both components, particularly in patients with renal impairment. Treatment is primarily supportive and symptomatic.

Storage

Store at room temperature (20-25°C or 68-77°F), in a tight, light-resistant container. Keep away from moisture and excessive heat. Do not freeze the oral suspension. Keep out of reach of children and pets. Do not use after the expiration date printed on the packaging. Properly discard any unused medication after the completion of therapy.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Bactrim is a prescription medication and should only be used under the supervision of a qualified healthcare professional. The patient must consult their physician for diagnosis, appropriate treatment, and dosage instructions tailored to their specific medical condition. Never initiate, adjust, or discontinue medication without professional guidance.

Reviews

“Bactrim remains a cornerstone in our antimicrobial arsenal, particularly for UTIs and PCP prophylaxis. Its dual mechanism offers reliable efficacy, though vigilance for hematologic and dermatologic adverse events is paramount in clinical practice.” – Infectious Disease Specialist, 15 years experience.

“In pediatric otitis media cases caused by susceptible H. influenzae or S. pneumoniae, Bactrim provides effective coverage. We monitor renal function and CBC routinely during courses exceeding 10 days.” – Pediatric Pharmacist.

“While an old drug, its utility in managing opportunistic infections in immunocompromised hosts is undeniable. The hyperkalemia risk in elderly patients on polypharmacy requires careful electrolyte monitoring.” – Clinical Pharmacologist.