Dosing and uses of Primsol, Proloprim (trimethoprim)
Adult dosage forms and strengths
oral solution
- 50mg/5mL
tablets
- 100mg
Susceptible Infections
100 mg PO q12hr
Renal Impairment
CrCl 15-30 mL/min: 50 mg q12hr
CrCl <15 mL/min: 100 mg q24hr or avoid use
Other Information
See also combo with sulfamethoxazole (Cotrim/Bactrim/Septra/Sulfatrim)
Available also as a combo with sulfadiazine (Coptin) in Canada
Other Indications and Uses
UTI caused by E. coli, Enterobacter spp., K. pneumoniae, P. mirabilis, coagulase-neg Staphylococcus spp.
Pediatric dosage forms and strengths
<12 years old: safety and efficacy not established
Primsol, Proloprim (trimethoprim) adverse (side) effects
Frequency not defined
Aseptic meningitis
Fever
Maculopapular rash (3-7% at 200 mg/day; incidence higher with larger daily doses)
Erythema multiforme
Exfoliative dermatitis
Pruritus (common)
Phototoxic skin eruptions
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Hyperkalemia
Hyponatremia
Epigastric distress
Glossitis
Nausea
Vomiting
Leukopenia
Megaloblastic anemia
Methemoglobinemia
Neutropenia
Thrombocytopenia
Liver enzyme elevation
Cholestatic jaundice
BUN and creatinine increased
Anaphylaxis
Hypersensitivity reactions
Warnings
Contraindications
Hypersensitivity
Megaloblastic anemia due to folate deficiency
Cautions
Decreases urinary potassium excretion; may cause hyperkalemia, particularly with high doses, renal insufficiency, or when combined with other drugs that cause hyperkalemia
Large doses or long term therapy may interfere with hematopoiesis; monitor for signs/symptoms of hematologic disorders
Prolonged use may cause fungal or bacterial superinfection, including clostridium difficile-associated diarrhea and pseudomembranous colitis; may occur >2 months postantibiotic treatment
Hypersensitivity reactions reported
Use caution in patients with renal or hepatic impairment
Use caution in patients with potential for folate deficiency, including malnourished, chronic anticonvulsant therapy, or elderly; folates may be administered concomitantly without interfering with antibacterial action of trimethoprim
Some dosage forms may contain benzyl alcohol and derivatives; avoid in neonates
Not indicated for prophylactic or prolonged administration in otitis media at any age
Pregnancy and lactation
Pregnancy category: C
Lactation: enters breast milk
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Primsol, Proloprim (trimethoprim)
Absorption: readily and extensive
Distribution: widely into body tissues and fluids (middle ear, prostate, bile, aqueous humor, CSF); crosses placenta; enters breast milk
Protein binding: 42-46%
Half-life elimination: 8-14 hr; prolonged in renal impairment
Time to peak, serum: 1-4 hr
Metabolism: partially hepatic
Excretion: urine (60-80%) as unchanged drug
Mechanism of action
Inhibits dihydrofolate reductase, which in turn inhibits folic acid reduction to tetrahydrofolate, causing inhibition of microorganism growth
