ACETAMINOPHEN, CAFFEINE AND DIHYDROCODEINE BITARTRATE
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur especially in CYP2D6 ultra-rapid metabolizers.
Acetaminophen: inhibits cyclooxygenase (COX) activity, reducing prostaglandin synthesis; analgesic and antipyretic. Caffeine: adenosine receptor antagonist; enhances analgesic effect. Dihydrocodeine: mu-opioid receptor agonist; produces analgesia via central opioid receptors.
| Metabolism | Acetaminophen: primarily hepatic via glucuronidation and sulfation; minor CYP2E1, CYP1A2, CYP3A4. Caffeine: hepatic via CYP1A2. Dihydrocodeine: O-demethylation to dihydromorphine via CYP2D6; also via CYP3A4. |
| Excretion | Acetaminophen: renal excretion of metabolites (glucuronide 60%, sulfate 30%, cysteine/mercapturate 8%), <5% unchanged. Caffeine: renal excretion of metabolites (1-methyluric acid, 1-methylxanthine, etc.), <2% unchanged. Dihydrocodeine: renal excretion of metabolites (dihydrocodeine-6-glucuronide, nordihydrocodeine, dihydromorphine), ~20% unchanged. Overall, predominantly renal (≥85%), minor biliary/fecal. |
| Half-life | Acetaminophen: 2-3 hours (normal), prolonged in hepatic impairment. Caffeine: 3-6 hours (adults), prolonged in liver disease or with oral contraceptives. Dihydrocodeine: 3.5-6 hours (terminal). Clinical context: q6h dosing interval appropriate; accumulation risk in renal/hepatic impairment. |
| Protein binding | Acetaminophen: 10-25% (albumin). Caffeine: 25-36% (albumin). Dihydrocodeine: ~20-30% (albumin and α1-acid glycoprotein). |
| Volume of Distribution | Acetaminophen: 0.7-1.0 L/kg. Caffeine: 0.5-0.8 L/kg. Dihydrocodeine: 1.0-1.5 L/kg. Clinical meaning: moderate distribution, potential for central nervous system penetration. |
| Bioavailability | Acetaminophen: oral 75-85%. Caffeine: oral ~100%. Dihydrocodeine: oral ~20-30% (first-pass metabolism; extended-release formulations have altered bioavailability). |
| Onset of Action | Oral: acetaminophen 30-60 min, caffeine 30-60 min, dihydrocodeine 30-60 min. Peak effects: acetaminophen 1-2 h, caffeine 45-60 min, dihydrocodeine 1-2 h. |
| Duration of Action | Analgesic: 4-6 hours (dihydrocodeine 3-6 h, acetaminophen 4-6 h). Stimulant (caffeine): 4-6 hours. Clinical note: Duration may be shorter in rapid metabolizers of dihydrocodeine (CYP2D6) or due to caffeine tolerance. |
1-2 tablets (each containing acetaminophen 300 mg, caffeine 30 mg, dihydrocodeine bitartrate 20 mg) orally every 4-6 hours as needed for pain; maximum 8 tablets per day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: administer every 6 hours; GFR 10-30 mL/min: administer every 8 hours; GFR <10 mL/min: administer every 12 hours; avoid in severe impairment due to dihydrocodeine accumulation. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% or extend interval to every 8 hours; Child-Pugh C: avoid use due to acetaminophen hepatotoxicity and dihydrocodeine accumulation. |
| Pediatric use | Not recommended for children under 12 years due to dihydrocodeine risks; for adolescents 12-18 years: 1 tablet orally every 4-6 hours as needed, maximum 4 tablets per day (weight-based dosing not established). |
| Geriatric use | Initiate with 1 tablet orally every 6 hours; caution due to increased sensitivity to opioids and hepatotoxicity from acetaminophen; maximum 4 tablets per day; monitor renal and hepatic function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk Life-threatening respiratory depression may occur especially in CYP2D6 ultra-rapid metabolizers.
| FDA category | Positive |
| Breastfeeding | Acetaminophen: Excreted in breast milk (M/P ratio ~0.9); safe at therapeutic doses. Caffeine: Excreted (M/P ~0.5-0.8); moderate intake (<300 mg/day) generally safe. Dihydrocodeine: Excreted in low levels; however, interindividual variability in metabolism (CYP2D6) may lead to higher morphine concentrations in some infants; risk of neonatal respiratory depression. M/P ratio not well established for dihydrocodeine. Use with caution, monitor infant for sedation and feeding difficulties. |
■ FDA Black Box Warning
Risk of addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion of acetaminophen can cause fatal hepatotoxicity; concomitant use with benzodiazepines or CNS depressants may cause profound sedation, respiratory depression, coma, and death; neonatal opioid withdrawal syndrome with prolonged use during pregnancy.
| Common Effects | cough |
| Serious Effects |
Hypersensitivity to any component; significant respiratory depression; acute or severe bronchial asthma; GI obstruction; suspected surgical abdomen; concomitant use with MAOIs or within 14 days; severe hepatic impairment.
| Precautions | Addiction, abuse, and misuse; respiratory depression; acetaminophen hepatotoxicity; drug interaction with benzodiazepines and CNS depressants; neonatal opioid withdrawal syndrome; risk of serotonin syndrome; severe hypotension; adrenal insufficiency; use in patients with head injury or increased intracranial pressure; seizures; avoid in patients with severe hepatic impairment. |
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| Teratogenic Risk | Acetaminophen: Generally considered low risk; no consistent evidence of teratogenicity. Caffeine: High doses (>200 mg/day) associated with increased miscarriage risk; limited data on malformations. Dihydrocodeine: Opioid; first trimester: increased risk of neural tube defects (OR 2.0-2.5); third trimester: risk of neonatal opioid withdrawal syndrome (NOWS). Overall, combination product should be used only if benefit outweighs risks. |
| Fetal Monitoring | Maternal: Monitor liver function (acetaminophen toxicity), blood pressure (caffeine), respiratory rate and sedation (dihydrocodeine). Fetal: Ultrasound for growth restriction and congenital anomalies if prolonged use; third trimester: fetal heart rate monitoring and assessment for NOWS (irritability, tremors, feeding intolerance). |
| Fertility Effects | Limited data. Acetaminophen: Some studies suggest prolonged use may interfere with ovulation (prostaglandin inhibition). Caffeine: High intake (>300 mg/day) associated with delayed conception and increased risk of infertility (OR 1.5). Dihydrocodeine: Opioids may disrupt hypothalamic-pituitary-gonadal axis leading to menstrual irregularities and anovulation. Overall, uncertain clinical significance with short-term use. |
| Food/Dietary | Avoid alcohol; may increase risk of hepatotoxicity and CNS depression. High-fat meals may delay absorption but do not significantly affect overall exposure. Caffeine-containing foods and beverages may increase stimulant effects. |
| Clinical Pearls | Dihydrocodeine is a prodrug requiring CYP2D6 metabolism to active metabolites; poor metabolizers may have reduced efficacy while ultrarapid metabolizers risk toxicity. Caffeine potentiates analgesia and may cause insomnia with evening use. Do not exceed 8 tablets per 24 hours due to acetaminophen hepatotoxicity risk. Use with caution in elderly and patients with renal impairment. |
| Patient Advice | Take with food if stomach upset occurs. · Avoid alcohol and products containing acetaminophen to prevent liver damage. · Do not exceed 8 tablets in 24 hours. · May cause drowsiness; avoid driving or operating machinery until you know how this medication affects you. · If you have a history of drug dependence, use with caution as dihydrocodeine can be habit-forming. |