What is co-trimoxazole used for?

co-trimoxazole is evaluated for the following indications with varying evidence strength: Pneumocystis pneumonia treatment (evidence tier A), Pneumocystis pneumonia prophylaxis (evidence tier A), Uncomplicated acute cystitis in women (evidence tier B). See the full indication matrix with dosing and citations above on this page.

What are the side effects of co-trimoxazole?

Common side effects of co-trimoxazole (≥ 1 in 100): Nausea, vomiting, diarrhea, Skin rash, pruritus, Hyperkalemia due to inhibition of collecting duct secretion, Creatinine rise due to competition with trimethoprim tubular secretion (does not reflect true GFR drop). See the Safety section for uncommon and serious reactions.

Who should not take co-trimoxazole?

co-trimoxazole is contraindicated in: Hypersensitivity to sulfonamides or trimethoprim; Glucose-6-phosphate dehydrogenase deficiency; Severe hepatic impairment with active hepatitis; eGFR below 15 mL/min/1.73 m² without monitoring capability; Folate deficiency-related megaloblastic anemia. Full list in the Safety section.

FDA category D. FDA category D. Sulfamethoxazole displaces bilirubin from albumin and increases the risk of kernicterus in the newborn when used in the third trimester. Trimethoprim is a folate antagonist that, in the first trimester, raises the risk of neural tube defects and cardiovascular malformations. The drug is not used in the first and third trimesters. In the second trimester it is given only for vital indications with mandatory folic acid 5 mg daily.

Pneumocystis pneumonia prophylaxis

Primera línea

Co-trimoxazole is the first-line agent for Pneumocystis jirovecii prophylaxis in HIV patients with CD4 below 200 cells/uL, after HSCT, in solid organ transplant recipients, and in patients on prolonged high-dose glucocorticoids. CDC/NIH/ 2024 recommend co-trimoxazole 80/400 mg daily or 160/800 mg three times weekly. The 2014 Cochrane review confirms an 85% reduction in PJP incidence in non-HIV immunocompromised patients.

Prophylaxis continues until CD4 recovers above 200 cells/uL and viral load is suppressed. In transplant recipients, at least 6-12 months depending on protocol.

Pneumocystis pneumonia treatment

Primera línea

Co-trimoxazole at 15-20 mg/kg/day by trimethoprim, divided into 3-4 doses, for 21 days is the first-line treatment of Pneumocystis pneumonia. CDC/NIH/ 2024 recommend this regimen for both HIV-associated PJP and non-HIV patients. With PaO2 below 70 mm Hg or alveolar-arterial gradient above 35 mm Hg, prednisolone 40 mg twice daily is added. Alternatives for intolerance include pentamidine and primaquine plus clindamycin.

Sources

MRSA skin and soft tissue infection

Primera línea

For community-acquired MRSA skin and soft tissue infections of mild to moderate severity (furuncle, drained abscess, limited cellulitis), co-trimoxazole 1-2 DS tablets twice daily for 5-10 days is a first-line oral option. 2011 lists the drug alongside doxycycline and clindamycin. Co-trimoxazole is preferred when clindamycin is resistant or intolerable. Severe forms require parenteral vancomycin or linezolid.

Sources

Uncomplicated acute cystitis in women

Primera línea

Co-trimoxazole 160/800 mg twice daily for 3 days is one of the first-line options for acute uncomplicated cystitis in non-pregnant women in regions where local E. coli resistance is below 20%. /ESCMID 2011 lists the drug alongside nitrofurantoin and fosfomycin. In Russia, 2022 monitoring data show E. coli resistance to co-trimoxazole above 25%, so the drug is more often used as an alternative when susceptibility is confirmed.

Not used in pregnant women in the first and third trimesters. Dose adjustment is required at eGFR below 30 mL/min/1.73 m².

Sources

Acute viral upper respiratory infection

No recomendado

For acute viral upper respiratory infection and uncomplicated common cold, co-trimoxazole is not prescribed. The antibiotic does not shorten symptom duration or prevent bacterial complications, while carrying risks of rash, hematologic complications, and selection of resistant strains. "Just-in-case" prescribing for URI is an example of irrational antibiotic use.

Sources

Cuándo y cómo tomar

Taken with meals or immediately after, washed down with a full glass of water (200-250 mL). Good hydration (at least 1.5-2 L/day) reduces crystalluria risk. Dosing is twice daily with a 12-hour interval. Combined with folic acid 5 mg/day in the elderly and during prolonged therapy to reduce cytopenia risk.

Titulación de dosis

Standard doses by indication: UTI and travelers' diarrhea – 160/800 mg twice daily; MRSA skin infections – 160/800 mg twice daily; PJP treatment – 15-20 mg/kg/day by trimethoprim in 3-4 doses; PJP prophylaxis – 80/400 mg daily or 160/800 mg three times weekly. At eGFR 15-30 mL/min/1.73 m², the dose is halved. At eGFR below 15 mL/min/1.73 m², the drug is not used except in monitored hemodialysis patients.

Monitorización

Before starting therapy, check CBC, creatinine, eGFR, potassium, and liver enzymes. By day 7-10 of prolonged therapy and every 2 weeks thereafter, repeat CBC, creatinine, and potassium. In the elderly, with concomitant ACEi/ARB or potassium-sparing diuretics, monitor potassium every 3-5 days during the first 2 weeks of therapy. Rash is an indication to stop the drug immediately and assess severity (Stevens-Johnson risk).

Situaciones especiales

With concomitant warfarin, INR rises – check every 3 days and reduce warfarin dose by 25-50%. With concomitant methotrexate, myelosuppression risk increases; co-trimoxazole is contraindicated with high-dose methotrexate. In HIV patients tolerance is worse: rash occurs in 30-60%, and desensitization protocols are considered to continue PJP therapy.

Mitos frecuentes

Myth: "biseptol is old and safe, can be used for any URI". Fact: useless in viral infections, while carrying rare but severe adverse effects (Stevens-Johnson, agranulocytosis). "Prophylactic" prescribing for URI is unjustified.

Myth: "creatinine rise on co-trimoxazole means renal failure". Fact: trimethoprim blocks tubular creatinine secretion, so creatinine rises by 10-20% without a true eGFR drop. Use cystatin C or repeat eGFR 7 days after discontinuation to assess kidney function.

Myth: "can be taken during partner's pregnancy". Fact: contraindicated in the first and third trimesters because of malformation and kernicterus risks.

Folate

Trimethoprim is a dihydrofolate reductase inhibitor and impairs conversion of folic acid to its active form. In long therapy or in patients with baseline deficiency, megaloblastic anemia, leukopenia, and thrombocytopenia develop. Prevention: folic acid 5 mg daily for courses longer than 14 days, in the elderly, and with concurrent methotrexate, phenytoin, or antiepileptic drugs.

Fuente: UpToDate: Trimethoprim-sulfamethoxazole: an overview (2024)

Mayor

Enalapril

Inhibidores de la enzima convertidora de angiotensina (IECA)

Mecanismo

Триметоприм блокирует эпителиальные Na-каналы в собирательных трубочках по механизму амилорида, что вызывает гиперкалиемию. Аддитивно с .

Manejo

Контроль K на 4-й и 7-й день курса. У пожилых и при – избегать длительных курсов.

Fuentes

PubMed: Trimethoprim-sulfamethoxazole and risk of sudden death among patients taking spironolactone or ACE inhibitors (2014)

Detalles de la pareja →

Contraindicaciones

Hypersensitivity to sulfonamides or trimethoprim
Glucose-6-phosphate dehydrogenase deficiency
Severe hepatic impairment with active hepatitis
eGFR below 15 mL/min/1.73 m² without monitoring capability
Folate deficiency-related megaloblastic anemia
First and third trimester of pregnancy
Children under 6 weeks
Concurrent use with high-dose methotrexate

Reacciones adversas graves

Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS
Fulminant hepatitis, hepatic failure
Agranulocytosis, aplastic anemia
Severe hyperkalemia in elderly patients on ACEi/ARB and spironolactone

Reacciones adversas frecuentes

Nausea, vomiting, diarrhea
Skin rash, pruritus
Hyperkalemia due to inhibition of collecting duct secretion
Creatinine rise due to competition with trimethoprim tubular secretion (does not reflect true GFR drop)

Reacciones adversas poco frecuentes

Drug-induced hepatitis, cholestasis
Leukopenia, thrombocytopenia, megaloblastic anemia (especially in the elderly and folate-deficient)
Crystalluria with inadequate urine output
Hyponatremia due to SIADH

EmbarazoFDA D

FDA category D. Sulfamethoxazole displaces bilirubin from albumin and increases the risk of kernicterus in the newborn when used in the third trimester. Trimethoprim is a folate antagonist that, in the first trimester, raises the risk of neural tube defects and cardiovascular malformations. The drug is not used in the first and third trimesters. In the second trimester it is given only for vital indications with mandatory folic acid 5 mg daily.

Lactancia

In healthy term infants older than 1 month, breastfeeding is compatible with maternal co-trimoxazole use. In neonates with hyperbilirubinemia, prematurity, or G6PD deficiency, concurrent use is avoided.

co-trimoxazole

Mecanismo de acción

Indicaciones

Pneumocystis pneumonia prophylaxis

Pneumocystis pneumonia treatment

MRSA skin and soft tissue infection

Uncomplicated acute cystitis in women

Acute viral upper respiratory infection

Notas prácticas

Cuándo y cómo tomar

Titulación de dosis

Monitorización

Situaciones especiales

Mitos frecuentes

Interacciones con nutrientes

Folate

Interacciones farmacológicas

Enalapril

Seguridad

Contraindicaciones

Reacciones adversas graves

Reacciones adversas frecuentes

Reacciones adversas poco frecuentes

EmbarazoFDA D

Lactancia

Preguntas frecuentes