trimethoprim

Therapeutic Classification: anti-infectives

Pharmacologic Classification: folate antagonists

Indications ⬆ ⬇

REMS

Uncomplicated urinary tract infections.
Uncomplicated otitis media in children.

Unlabeled Use:

Prophylaxis of chronic recurrent urinary tract infections.
Mild to moderate
Pneumocystis jirovecii
pneumonia (in combination with dapsone).

Action ⬆ ⬇

Interferes with bacterial folic acid synthesis.

Therapeutic effects:

Bactericidal action against susceptible organisms.

Spectrum:

Some gram-positive pathogens, including:
- Staphylococcus saprophyticus.
Gram-negative spectrum includes the following Enterobacteriaceae:
- Enterobacter,
- Escherichia coli,
- Klebsiella pneumoniae,
- Proteus mirabilis,
Also active against Pneumocystis jiroveci.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Widely distributed.

Metabolism/Excretion: 80% excreted unchanged in the urine; 20% metabolized by the liver.

Half-Life: 8–11 hr (↑ in renal impairment).

Time/Action Profile ⬆ ⬇

(plasma concentrations)

ROUTE	ONSET	PEAK	DURATION
PO	rapid	1–4 hr	12–24 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Megaloblastic anemia secondary to folate deficiency.

Use Cautiously in:

Renal impairment (dose ↓ required if CCr ≤30 mL/min);
Debilitated patients;
Severe hepatic impairment;
Folate deficiency;
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Children 12 yr (effectiveness as a single agent not established); children 6 mo (safety and effectiveness not established).

Adv. Reactions/Side Effects ⬆ ⬇

Derm: pruritus, rash

GI: altered taste, epigastric discomfort, glossitis, nausea, vomiting, drug-induced hepatitis

Hemat: megaloblastic anemia, neutropenia, thrombocytopenia

Misc: fever

Interactions ⬆ ⬇

Drug-drug:

↑risk of folate deficiency when used with phenytoin or methotrexate.
↑risk of bone marrow depression when used with antineoplastics or radiation therapy.
Rifampin may ↓ effectiveness by ↑ elimination.

Route/Dosage ⬆ ⬇

Urinary Tract Infections

PO (Adults and Children ≥12 yr): 100 mg every 12 hr or 200 mg as a single daily dose.

Renal Impairment

PO (Adults ): CCr 15–30 mL/min: 50 mg every 12 hr (for urinary tract infections).

Otitis Media

PO (Children >6 mo): 5 mg/kg every 12 hr.

Prophylaxis of Chronic Urinary Tract Infections

PO (Adults ): 100 mg/day as a single dose.

Pneumocystis jirovecii Pneumonia

PO (Adults ): 20 mg/kg/day for 21 days.

Availability ⬆ ⬇

(Generic available)

Tablets: 100 mg; 200 mg
In combination with: sulfamethoxazole. See trimethoprim/sulfamethoxazole monograph.

Assessment ⬆ ⬇

Assess patient for urinary tract infection (fever, cloudy urine, frequency, urgency, pain and burning on urination) or other signs of infection at beginning of and throughout therapy.
Obtain specimens for culture and sensitivity prior to initiating therapy. First dose may be given before receiving results.
Monitor intake and output ratios. Fluid intake should be sufficient to maintain urine output of at least 1200–1500 mL daily.

Lab Test Considerations:

May produce elevated serum bilirubin, creatinine, BUN, AST, and ALT.
- Monitor CBC and urinalysis periodically throughout therapy. Therapy should be discontinued if blood dyscrasias occur.

Implementation ⬆ ⬇

PO: Administer on an empty stomach, at least 1 hr before or 2 hr after meals, with a full glass of water. May be administered with food if GI irritation occurs.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take medication and to finish medication completely as directed, even if feeling better. Take missed doses as soon as remembered, with subsequent doses spaced evenly apart. Advise patient that sharing of this medication may be dangerous.
Advise patient to notify health care professional if skin rash, sore throat, fever, mouth sores, or unusual bleeding or bruising occurs. Leucovorin (folinic acid) may be administered if folic acid deficiency occurs.
Instruct patient to notify health care professional if symptoms do not improve.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding. Fetal exposure during pregnancy may affect folate metabolism.
Emphasize the importance of routine follow-up exams to evaluate progress.

Evaluation/Desired Outcomes ⬆ ⬇

Resolution of the signs and symptoms of infection. Therapy is usually required for 10–14 days for resolution of urinary tract infection.
Decreased incidence of urinary tract infections during prophylactic therapy.

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Pronunciation ⬇

Classifications ⬆ ⬇