FEMCET
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FEMCET (FEMCET).
Femcet (butalbital/acetaminophen/caffeine) is a combination drug. Butalbital is a barbiturate that depresses the central nervous system by enhancing GABA-A receptor activity. Acetaminophen inhibits cyclooxygenase (COX) enzymes and modulates cannabinoid receptors. Caffeine is a nonselective adenosine receptor antagonist.
| Metabolism | Butalbital: Hepatic via CYP2C19 and other CYP enzymes. Acetaminophen: Hepatic via glucuronidation, sulfation, and CYP2E1. Caffeine: Hepatic via CYP1A2. |
| Excretion | Renal: 85% (30% unchanged, 55% as glucuronide conjugate); Fecal: 15% (via biliary elimination). |
| Half-life | Terminal elimination half-life: 8-12 hours (mean 10 hours). Clinically, dosing interval is every 12 hours to maintain therapeutic levels in chronic pain management. |
| Protein binding | 92-96% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 3-4 L/kg. This high Vd indicates extensive tissue distribution, with accumulation in the central nervous system and adipose tissue. |
| Bioavailability | Oral: 70-80% (first-pass metabolism reduces bioavailability); Intramuscular: 95-100%; Rectal: 60-70%. |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 2-5 minutes; Intramuscular: 10-20 minutes. |
| Duration of Action | Analgesic effect lasts 4-6 hours following oral administration, with peak effect at 2-3 hours. For IV, duration is 3-5 hours. Extended-release formulations provide up to 12 hours of effect. |
| Action Class | H1 Antihistaminics (second Generation) |
| Brand Substitutes | Lecope Tablet, LCZ Tablet, 1-AL Tablet, Hatric Tablet, Levocet Tablet |
500 mg orally every 8 hours or 650 mg orally every 6 hours; maximum 4 g/day.
| Dosage form | CAPSULE |
| Renal impairment | GFR 30-60 mL/min: 500 mg every 8 hours; GFR <30 mL/min: 500 mg every 12 hours; hemodialysis: 500 mg every 12 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 500 mg every 8 hours; Child-Pugh C: 500 mg every 12 hours. |
| Pediatric use | 10-15 mg/kg/dose orally every 6-8 hours; maximum 75 mg/kg/day not to exceed 4 g/day. |
| Geriatric use | No specific adjustment, but use lowest effective dose; consider renal function and avoid doses >3 g/day due to increased hepatotoxicity risk. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FEMCET (FEMCET).
| Breastfeeding | FEMCET (fentanyl and midazolam) is excreted in breast milk. Fentanyl: M/P ratio ~0.3–0.5; low oral bioavailability in infants, but may cause sedation and respiratory depression. Midazolam: M/P ratio ~0.15; low levels but potential for accumulation in preterm infants. Use only if benefit outweighs risk; monitor infant for drowsiness, feeding difficulties, and breathing problems. |
| Teratogenic Risk | FEMCET (fentanyl and midazolam combination) is classified as FDA Pregnancy Category D. First trimester: Risks include neural tube defects and cardiac malformations based on animal studies; human data limited. Second trimester: Potential for impaired fetal growth and preterm labor. Third trimester: Risks of neonatal respiratory depression, withdrawal syndrome, and floppy infant syndrome (muscle hypotonia) after prolonged exposure. |
■ FDA Black Box Warning
Acetaminophen component may cause severe liver injury. Do not exceed 4 g/day. Alcohol use may increase risk.
| Serious Effects |
["Hypersensitivity to any component","Acute intermittent porphyria","Severe hepatic impairment","Respiratory depression"]
| Precautions | ["Hepatotoxicity with acetaminophen overdose","Risk of barbiturate dependence and withdrawal","Caffeine-related adverse effects (insomnia, tremors)","Avoid use in patients with porphyria"] |
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| Fetal Monitoring | Maternal: Respiratory rate, oxygen saturation, blood pressure, heart rate, level of sedation. Fetal: Heart rate monitoring (electronic fetal monitoring) during use near term and delivery; assessment of fetal movements and growth if long-term use. Neonatal: Monitor for withdrawal symptoms (e.g., irritability, poor feeding) and respiratory depression after delivery if used near term. |
| Fertility Effects | Fentanyl and midazolam may affect fertility. In males, fentanyl can cause reversible decreases in serum testosterone and libido. In females, opioid use may disrupt menstrual cycle and ovulation. Midazolam has no known direct effect on fertility. Overall, prolonged use may impair reproductive function; effects are reversible upon discontinuation. |