• Treatment of uncomplicated urinary tract infections.
• Treatment of uncomplicated otitis media in children.

Unlabeled Uses:

• Prophylaxis of chronic recurrent urinary tract infections.
• Treatment of head lice.
• With dapsone in the management of mild to moderate Pneumocystis jirovecii pneumonia (PCP).

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: Lactation: Pedi: Pregnancy, lactation, or children <12 yr (safety as a single agent not established).

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

Derm: pruritus, rash.

Hemat: megaloblastic anemia, neutropenia, thrombocytopenia.
Misc: fever.

Drug-Drug:

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

(Generic available)

• Tablets: 100 mg;
• Oral solution (bubblegum flavor): 50 mg/5 mL;
• In combination with: sulfamethoxazole. See Trimethoprim/Sulfamethoxazole monograph.

Treatment of Urinary Tract Infections

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

Treatment of Otitis Media

• PO (Children >6 mos): 5 mg/kg q 12 hr.

Prophylaxis of Chronic Urinary Tract Infections

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

Pneumocystis jirovecii Pneumonia

• PO (Adults): 20 mg/kg/day with 100 mg dapsone daily for 21 days (unlabeled).

Primsol

• Interferes with bacterial folic acid synthesis.

• 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.

Therapeutic Classification: anti-infectives

Pharmacologic Classification: folate antagonists

Absorption: Well absorbed following oral administration.

Distribution: Widely distributed. Crosses the placenta and is distributed into breast milk in high concentrations.

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

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

(blood levels)

• 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.
• Emphasize the importance of routine follow-up exams to evaluate progress.

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