TERFONYL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TERFONYL (TERFONYL).
TERFONYL is a sulfonamide antibiotic that inhibits bacterial dihydropteroate synthase, thereby blocking folate synthesis and bacterial DNA replication.
| Metabolism | Hepatic via acetylation and glucuronidation; primarily excreted renally as metabolites. |
| Excretion | Renal excretion accounts for 70-90% of elimination as unchanged drug via glomerular filtration and tubular secretion; biliary/fecal excretion constitutes 10-30%. |
| Half-life | Terminal elimination half-life is 2.5-4 hours in adults with normal renal function; prolonged to 12-24 hours in severe renal impairment (CrCl < 30 mL/min). |
| Protein binding | 65-75% bound primarily to albumin. |
| Volume of Distribution | 0.15-0.25 L/kg, indicating distribution mainly into extracellular fluid; does not readily penetrate cerebrospinal fluid unless meninges inflamed. |
| Bioavailability | Oral: 70-90% (complete absorption, but first-pass metabolism reduces systemic exposure). |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 5-15 minutes. |
| Duration of Action | Oral: 6-12 hours; Intravenous: 6-12 hours. Clinical effect correlates with serum levels above MIC; dosing interval adjusted in renal impairment. |
2 g intravenously every 12 hours over 24 hours for susceptible infections.
| Dosage form | SUSPENSION |
| Renal impairment | CrCl >50 mL/min: no adjustment; CrCl 20-50 mL/min: 2 g every 24 hours; CrCl <20 mL/min: 2 g every 48 hours or 1 g every 24 hours. |
| Liver impairment | No specific recommendations; use with caution in severe hepatic impairment (Child-Pugh C) due to limited data. |
| Pediatric use | Infants and children: 40 mg/kg intravenously every 12 hours (maximum 2 g per dose). |
| Geriatric use | Cautious dosing based on renal function; monitor CrCl and adjust accordingly due to age-related decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TERFONYL (TERFONYL).
| Breastfeeding | Excreted into breast milk; M/P ratio 0.5. Use caution; potential for adverse effects in nursing infant. |
| Teratogenic Risk | First trimester: Increased risk of neural tube defects and cardiovascular malformations. Second and third trimesters: Risk of premature closure of ductus arteriosus and oligohydramnios. |
| Fetal Monitoring | Monitor fetal ultrasound for ductus arteriosus patency and amniotic fluid volume. Assess maternal renal function and blood pressure. |
■ FDA Black Box Warning
Sulfonamides, including TERFONYL, have been associated with severe hypersensitivity reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis. Avoid use in patients with known sulfonamide allergy.
| Serious Effects |
Hypersensitivity to sulfonamides; porphyria; severe hepatic or renal impairment; pregnancy (particularly near term); lactation.
| Precautions | Risk of severe cutaneous adverse reactions; hemolytic anemia in G6PD deficiency; photosensitivity; renal impairment; hepatic impairment. |
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| Fertility Effects | May impair fertility due to ovarian toxicity and menstrual irregularities. |