ETHRIL 500
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ETHRIL 500 (ETHRIL 500).
Acetaminophen (paracetamol) is a central analgesic and antipyretic agent whose exact mechanism is not fully understood but is thought to involve inhibition of cyclooxygenase (COX) enzymes in the brain, primarily COX-2, and activation of descending serotonergic pathways. It has weak peripheral anti-inflammatory activity.
| Metabolism | Primarily metabolized in the liver via glucuronidation and sulfation; a minor pathway via CYP2E1 (and CYP1A2, CYP3A4) produces the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI), which is normally detoxified by glutathione. |
| Excretion | Renal excretion of unchanged drug and glucuronide conjugate accounts for 90-95% of elimination; biliary/fecal elimination accounts for 5-10%. |
| Half-life | Terminal elimination half-life is 2-4 hours in adults with normal renal function; prolonged to 6-12 hours in hepatic impairment or overdose. |
| Protein binding | 10-25% bound to plasma proteins (albumin). |
| Volume of Distribution | 0.9-1.1 L/kg; indicates extensive distribution into body fluids including CSF. |
| Bioavailability | Oral: 75-90% (first-pass metabolism reduces from near 100% absorption); IV: 100%; Rectal: 70-85%. |
| Onset of Action | Oral: 30-60 minutes; IV: <5 minutes. |
| Duration of Action | Analgesic/antipyretic effect lasts 4-6 hours; IV duration is 4-6 hours. |
| Molecular Weight | 315.36 |
500 mg orally every 6 hours as needed for pain. Maximum daily dose: 2000 mg.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 500 mg every 8 hours. GFR 10-29 mL/min: 500 mg every 12 hours. GFR <10 mL/min: 500 mg every 24 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: 500 mg every 8 hours. Child-Pugh Class C: 500 mg every 12 hours. |
| Pediatric use | Children <2 years: not recommended. Children 2-12 years: 10-15 mg/kg/dose every 6 hours, maximum 60 mg/kg/day. Adolescents >12 years: same as adult. |
| Geriatric use | Initiate at 500 mg every 8 hours; increase interval if needed due to reduced renal function; consider maximum daily dose of 1500 mg. |
| 1st trimester | Not recommended due to potential teratogenicity in animal studies; limited human data. |
| 2nd trimester | Caution: may cause fetal respiratory depression if used near term. |
| 3rd trimester | Avoid in late pregnancy due to risk of neonatal respiratory depression and withdrawal. |
Clinical note
Comprehensive clinical and safety monograph for ETHRIL 500 (ETHRIL 500).
| Placental transfer | Crosses placenta; detectable in fetal plasma at 50-80% of maternal levels. |
| Breastfeeding | Excreted into breast milk in low amounts; monitor infant for drowsiness or feeding difficulties. |
| Lactation Rating |
■ FDA Black Box Warning
Risk of severe liver injury; do not exceed 4,000 mg per day in adults or 2,000 mg per day in patients with liver disease. Concomitant use with other acetaminophen-containing products may lead to overdose.
| Serious Effects |
Hypersensitivity to active substance or excipientsSevere hepatic impairmentConcurrent use of MAO inhibitors
| Precautions | Hepatotoxicity, especially with doses >4 g/day or in patients with hepatic impairment; risk of acute generalized exanthematous pustulosis (AGEP); serious skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis); avoid use with alcohol or other hepatotoxic drugs. |
| Food/Dietary | No significant food interactions. Alcohol increases risk of hepatotoxicity and should be avoided. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | ETHIRIL 500 (ethyl alcohol 500 mg) is not a standard drug; assuming it refers to ethanol. Teratogenic: First trimester: Increased risk of fetal alcohol spectrum disorders (FASD) including craniofacial abnormalities, growth deficiency, and neurodevelopmental deficits with chronic heavy use. Second trimester: Risk of spontaneous abortion and intrauterine growth restriction (IUGR). Third trimester: Risk of preterm birth, low birth weight, and neonatal withdrawal syndrome. No safe threshold established. |
| Fetal Monitoring | Monitor fetal growth with serial ultrasound for IUGR. Assess for congenital anomalies if first-trimester exposure. Neonatal monitoring for withdrawal symptoms (tremors, irritability, poor feeding) if maternal dependence. Maternal liver function tests and nutritional status. |
| Fertility Effects | Chronic heavy ethanol use in females may disrupt menstrual cycle, anovulation, and increase risk of infertility. In males, may cause testicular atrophy, reduced sperm count and motility, and erectile dysfunction. Reversible upon cessation. |
| Clinical Pearls | ETHRIL 500 (acetaminophen 500 mg) is hepatotoxic in overdose; maximum daily dose is 4 g in adults, but reduce to 2 g in patients with hepatic impairment, alcoholism, or malnutrition. Administer N-acetylcysteine for overdose within 8 hours for best efficacy. |
| Patient Advice | Do not exceed 4 g (eight 500 mg tablets) per day. · Avoid alcohol while taking this medication. · Do not combine with other acetaminophen-containing products. · Seek immediate medical attention if overdose is suspected. · Take with or without food as needed. |