Sulfamethoxazole

Description

Sulfamethoxazole is a sulfonamide antibiotic that works by inhibiting the growth of bacteria. It is often used in combination with trimethoprim to enhance its effectiveness against a wide range of bacterial infections. Sulfamethoxazole targets specific enzymes in bacterial cells, disrupting their ability to produce essential folate necessary for growth and replication.

Uses / Indications

• Urinary tract infections (UTIs)
• Respiratory infections
• Gastrointestinal infections, including traveler’s diarrhea
• Pneumocystis pneumonia (PCP) in immunocompromised patients
• Certain types of ear infections
• Prevention of bacterial infections in certain conditions

Dosage and Administration

Adults:
Typical dosage is 800 mg of sulfamethoxazole combined with 160 mg of trimethoprim, taken twice daily for 10 to 14 days, depending on the infection.

Children:
Dosage is based on the child’s weight and the severity of the infection. Consult a healthcare provider for specific dosing guidelines.

Note: Dosage may vary based on medical condition or doctor’s advice.

How It Works (Mechanism of Action)

Sulfamethoxazole interferes with the synthesis of folate in bacteria by competitively inhibiting the enzyme dihydropteroate synthase. This action prevents the formation of dihydrofolate, a precursor necessary for nucleic acid synthesis, effectively impeding bacterial growth.

Side Effects

Common side effects:

• Nausea or vomiting
• Skin rash or itching
• Diarrhea
• Headache

Rare/serious side effects:

• Severe allergic reactions (rash, swelling, difficulty breathing)
• Blood disorders (such as agranulocytosis, thrombocytopenia)
• Liver toxicity (jaundice, dark urine)

Seek medical attention if serious side effects occur.

Precautions / Warnings

• Inform your doctor if you have a history of liver disease, kidney issues, or blood disorders.
• Use caution if you are pregnant, breastfeeding, or have asthma.
• Allergic reactions can occur, particularly in those with sulfa drug allergies.

Drug Interactions

Sulfamethoxazole may interact with:

• Anticoagulants (may enhance the effects)
• Certain anti-seizure medications
• Diuretics (may increase the risk of adverse reactions)
• Medications that affect liver enzymes

Always inform your healthcare provider about any other medications or supplements you’re taking.

Storage Instructions

• Store at room temperature (20°C–25°C / 68°F–77°F)
• Keep away from moisture, heat, and direct light
• Do not freeze liquid forms
• Keep out of reach of children

Missed Dose / Overdose

Missed a dose?
Take it as soon as you remember. If it’s almost time for your next dose, skip the missed one. Do not double up.

Overdose symptoms:

• Nausea or vomiting
• Severe headache
• Confusion or dizziness
• Unusual bleeding or bruising

Contact a poison control center or seek emergency medical help immediately.

Contraindications

• Known allergy to sulfamethoxazole or other sulfonamides
• Severe liver or kidney disease
• Pregnant women near term

Brand Names / Alternatives

• Bactrim
• Septra
• Cotrim
• Generic name: Sulfamethoxazole and trimethoprim