BUTAPAP
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BUTAPAP (BUTAPAP).
Butapap is a combination analgesic containing butalbital (barbiturate) and acetaminophen. Butalbital potentiates the analgesic effect of acetaminophen by increasing GABAergic inhibition in the central nervous system, while acetaminophen inhibits cyclooxygenase (COX) enzymes in the brain, reducing prostaglandin synthesis.
| Metabolism | Butalbital is metabolized primarily by hepatic cytochrome P450 enzymes (CYP2C9 and CYP2C19). Acetaminophen is primarily metabolized by glucuronidation (UGT1A1, UGT1A6, UGT1A9) and sulfation; a minor pathway via CYP2E1 produces N-acetyl-p-benzoquinone imine (NAPQI), a toxic intermediate. |
| Excretion | Renal excretion of unchanged drug and metabolites (primarily glucuronide conjugates): ~90%; biliary/fecal excretion: ~10%. |
| Half-life | Terminal elimination half-life: 2–3 hours; prolongation may occur in hepatic impairment. |
| Protein binding | ~25% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | ~0.7 L/kg; indicates distribution throughout total body water. |
| Bioavailability | Oral: 75–85% due to first-pass metabolism. |
| Onset of Action | Oral: 30–60 minutes; intravenous: 5–10 minutes. |
| Duration of Action | Analgesic effect: 3–4 hours; antipyretic effect: 4–6 hours. |
Butalbital/acetaminophen/caffeine: 1-2 capsules (50 mg butalbital/325 mg acetaminophen/40 mg caffeine) orally every 4 hours as needed, not to exceed 6 capsules per day.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment provided in labeling; use with caution in renal impairment. For acetaminophen component, reduce dose or extend interval in severe renal impairment (GFR <10 mL/min). |
| Liver impairment | Contraindicated in severe hepatic impairment. For mild to moderate impairment (Child-Pugh A or B), reduce acetaminophen dose; maximum 2 g/day. Use lowest effective dose of butalbital and monitor for CNS depression. |
| Pediatric use | Not recommended for use in pediatric patients due to safety concerns; efficacy not established. |
| Geriatric use | Start at low end of dosing range (1 capsule every 6 hours) due to increased sensitivity to butalbital and potential for acetaminophen hepatotoxicity; monitor renal and hepatic function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BUTAPAP (BUTAPAP).
| Breastfeeding | Butalbital enters breast milk; relative infant dose approximately 4-6%; milk-to-plasma ratio ~0.4. Monitor infant for sedation, poor feeding, or withdrawal upon cessation. American Academy of Pediatrics suggests caution; may be compatible with monitoring. |
| Teratogenic Risk | Butalbital (contained in Butapap) is a barbiturate; FDA Category D. First trimester: Risk of neural tube defects, oral clefts (odds ratio ~1.6). Second/third trimester: Chronic exposure may lead to fetal dependence, withdrawal, and floppy infant syndrome. Use only if benefit outweighs risk; consider alternative. |
■ FDA Black Box Warning
Acetaminophen has been associated with cases of acute liver failure, sometimes resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4000 milligrams per day, and often involve more than one acetaminophen-containing product.
| Serious Effects |
["Hypersensitivity to butalbital, acetaminophen, or any component of the formulation","Porphyria (butalbital can induce porphyrin synthesis)","Severe hepatic impairment or active liver disease"]
| Precautions | ["Hepatotoxicity: Risk of severe liver injury at high doses or with chronic use of acetaminophen.","Central nervous system depression: May impair mental or physical abilities; caution with alcohol or other CNS depressants.","Dependence: Butalbital can cause drug dependence; avoid abrupt discontinuation to prevent withdrawal."] |
| Food/Dietary | Avoid alcohol. Limit additional caffeine from coffee, tea, soda, chocolate to prevent excessive stimulation or insomnia. Grapefruit juice may increase caffeine levels; moderate consumption. |
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| Fetal Monitoring | Monitor maternal liver function and renal function if chronic use. Fetal ultrasound for growth restriction with prolonged use. In third trimester, assess fetal heart rate patterns if withdrawal suspected. Neonatal monitoring for withdrawal symptoms (irritability, seizures) for 48 hours after delivery if maternal use near term. |
| Fertility Effects | No direct studies on fertility. Barbiturates may induce cytochrome P450 enzymes affecting steroid hormone metabolism; theoretical risk of menstrual irregularities and anovulation. Chronic use may impair hypothalamic-pituitary-ovarian axis. |
| Clinical Pearls | Combination product: butalbital, acetaminophen, and caffeine. Butalbital is a barbiturate with high abuse potential; limit refills. Acetaminophen hepatotoxicity risk: do not exceed 4 g/day in adults, less in liver disease or alcohol use. Caffeine may exacerbate anxiety or insomnia. Avoid in porphyria. May cause sedation; warn against driving. |
| Patient Advice | Do not take more than prescribed; overdose risk of acetaminophen and butalbital. · Avoid alcohol; increases risk of liver damage and sedation. · May cause drowsiness; do not drive or operate machinery until you know how it affects you. · Do not use with other products containing acetaminophen (e.g., Tylenol). · Limit caffeine intake from other sources to avoid overstimulation. · If you have a history of drug or alcohol abuse, inform your doctor. · Take with food if stomach upset occurs. · Do not stop suddenly; withdrawal possible with prolonged use. |