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. |
| Molecular Weight | 250.28 |
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 | Terfonyl is contraindicated in first trimester due to risk of teratogenicity (neural tube defects, cardiovascular malformations). |
| 2nd trimester | Use only if benefit outweighs risk; crosses placenta and may cause fetal toxicity. |
| 3rd trimester | Contraindicated in third trimester due to risk of kernicterus and gray baby syndrome. |
Clinical note
Comprehensive clinical and safety monograph for TERFONYL (TERFONYL).
| Placental transfer | Readily crosses placenta; fetal concentrations reach 50-80% of maternal levels. |
| Breastfeeding | Excreted into breast milk; may cause hemolysis in G6PD-deficient infants. Discontinue breastfeeding or drug. |
| Lactation Rating |
■ 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 sulfonamidesPorphyriaSevere hepatic or renal impairmentInfants <2 months (except for congenital toxoplasmosis)Pregnancy (first and third trimesters)Breastfeeding
| Precautions | Risk of severe cutaneous adverse reactions; hemolytic anemia in G6PD deficiency; photosensitivity; renal impairment; hepatic impairment. |
| Food/Dietary | Avoid alcohol, which may cause disulfiram-like reaction. Take on an empty stomach (1 hour before or 2 hours after meals). Limit intake of foods high in vitamin K (e.g., spinach, kale) as it may reduce drug effect, though not a strong interaction; maintain consistent diet. No significant food interactions with Terfonyl specifically, but general sulfonamide guidelines apply. |
Loading safety data…
| L5 (Contraindicated) |
| 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. |
| Fertility Effects | May impair fertility due to ovarian toxicity and menstrual irregularities. |
| Clinical Pearls | Terfonyl is a sulfonamide antibiotic combination (sulfamethazine, sulfamerazine, sulfathiazole). Use with caution in patients with G6PD deficiency due to risk of hemolytic anemia. Monitor renal function and urine output; crystalluria can occur, so maintain high fluid intake. Avoid use in infants <2 months old. May potentiate warfarin and sulfonylureas. |
| Patient Advice | Take each dose with a full glass of water and drink extra fluids throughout the day to prevent kidney crystals. · Finish the entire prescribed course, even if you feel better. · Avoid prolonged sun exposure and use sunscreen; this drug may cause photosensitivity. · Stop medication and seek immediate medical help if you develop rash, fever, sore throat, or unusual bleeding/bruising. · Do not take if you are pregnant, breastfeeding, or have a sulfa allergy. |