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. |
| Molecular Weight | Acetaminophen: 151.16 Da; Caffeine: 194.19 Da; Dihydrocodeine bitartrate: 451.47 Da (dihydrocodeine base: 301.38 Da as free base); combination product specified as bitartrate salt. |
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 | Use only if potential benefit justifies risk; studies suggest association with minor malformations at high doses. |
| 2nd trimester | Use with caution; no clear evidence of fetal harm, but dihydrocodeine may cause respiratory depression in neonate if used near term. |
| 3rd trimester | Avoid prolonged use or high doses; risk of neonatal respiratory depression and withdrawal symptoms due to dihydrocodeine; acetaminophen is generally safe in short-term use. |
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 |
| Placental transfer | All components cross the placenta: acetaminophen (readily), caffeine (readily), dihydrocodeine (likely crosses, similar to other opioids). Degree of transfer for dihydrocodeine is not fully quantified but expected to be significant. |
■ 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 componentSevere respiratory depressionAcute or severe bronchial asthmaParalytic ileusConcurrent MAO inhibitors or within 14 daysKnown CYP2D6 ultra-rapid metabolizer (risk of opioid toxicity)
| 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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| Breastfeeding | Acetaminophen is considered safe in usual doses. Caffeine is excreted into breast milk but typical amounts are unlikely to affect the infant. Dihydrocodeine is excreted and may accumulate in breastfed infants; risk of respiratory depression and sedation, especially in mothers with CYP2D6 ultra-rapid metabolizer phenotype. Use with caution and monitor infant for drowsiness or respiratory distress. |
| Lactation Rating | L3 (Moderately Safe) - acetaminophen and caffeine are L1, but dihydrocodeine is L3 due to potential for infant sedation and respiratory depression. |
| 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. |