TRAMADOL HYDROCHLORIDE AND ACETAMINOPHEN
Clinical safety rating: avoid
CNS depressants including alcohol and benzodiazepines increase sedation risk MAOIs and other serotonergic drugs can cause serotonin syndrome.
Tramadol is a centrally acting synthetic opioid analgesic that binds to μ-opioid receptors and inhibits serotonin and norepinephrine reuptake. Acetaminophen inhibits cyclooxygenase (COX) enzymes in the central nervous system, reducing prostaglandin synthesis.
| Metabolism | Tramadol is metabolized primarily by CYP2D6 and CYP3A4 to active metabolite O-desmethyltramadol; also undergoes glucuronidation and sulfation. Acetaminophen is metabolized primarily via glucuronidation and sulfation, with minor oxidation by CYP2E1 and CYP3A4 to toxic N-acetyl-p-benzoquinone imine (NAPQI). |
| Excretion | Tramadol and its metabolites are primarily excreted renally (approximately 90% of total clearance), with about 30% excreted as unchanged drug and the remainder as metabolites. Fecal excretion accounts for less than 10%. Acetaminophen is primarily metabolized by the liver and excreted renally as glucuronide and sulfate conjugates; about 2-5% is excreted unchanged. Renal clearance of tramadol is reduced in renal impairment. |
| Half-life | Tramadol has a terminal elimination half-life of approximately 5–6 hours; for its active metabolite O-desmethyltramadol (M1), the half-life is about 7–9 hours. Acetaminophen has a half-life of 2–3 hours. These values are prolonged in hepatic or renal impairment and in elderly patients. |
| Protein binding | Tramadol: approximately 20% bound to plasma proteins. Acetaminophen: minimally bound (10–25%) to plasma proteins at therapeutic concentrations. |
| Volume of Distribution | Tramadol: Vd is approximately 2–3 L/kg (range 2.6–3.0 L/kg), indicating extensive tissue distribution. Acetaminophen: Vd is about 0.9–1.0 L/kg, consistent with its distribution primarily into total body water. |
| Bioavailability | Oral bioavailability of tramadol is approximately 70–75% due to first-pass metabolism; it is 100% bioavailable when administered intravenously. Acetaminophen has an oral bioavailability of 60–98%, typically ~85–90% due to first-pass metabolism. |
| Onset of Action | Oral: Onset of analgesic effect typically occurs within 30–60 minutes after administration, with peak effect at 2–3 hours. |
| Duration of Action | Analgesic duration is approximately 4–6 hours for the combination product, consistent with the dosing interval (every 4–6 hours as needed). Extended-release formulations may provide longer duration. |
Adults: 1-2 tablets (37.5-75 mg tramadol / 325-650 mg acetaminophen) orally every 4-6 hours as needed for pain; maximum 8 tablets/day (300 mg tramadol / 2600 mg acetaminophen).
| Dosage form | TABLET |
| Renal impairment | CrCl ≥30 mL/min: No adjustment. CrCl <30 mL/min: Increase dosing interval to 12 hours; maximum 4 tablets/day. Not recommended for patients with CrCl <10 mL/min. |
| Liver impairment | Child-Pugh Class A: Reduce dose or extend interval (e.g., 50 mg tramadol every 12 hours). Child-Pugh Class B or C: Use is not recommended due to risk of hepatotoxicity and increased tramadol exposure. |
| Pediatric use | Not recommended for children under 12 years. For adolescents ≥12 years: same as adult dosing; weight-based guidelines not established. |
| Geriatric use | Patients >65 years: Use with caution; reduce total daily dose (e.g., maximum 4 tablets/day) and increase dosing interval to 6-8 hours. For age >75 years or debilitated, consider further dose reduction. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants including alcohol and benzodiazepines increase sedation risk MAOIs and other serotonergic drugs can cause serotonin syndrome.
| FDA category | Positive |
| Breastfeeding | Acetaminophen enters breast milk in low levels (M/P ratio ~0.5-2). Tramadol passes into breast milk with relative infant dose ~0.9% of maternal weight-adjusted dose; M/P ratio ~0.8. Risk of infant sedation or withdrawal with high maternal doses or poor metabolizers of tramadol (CYP2D6). Use with caution, monitor infant for drowsiness, poor feeding, respiratory depression. |
| Teratogenic Risk |
■ FDA Black Box Warning
Risk of medication errors, addiction, abuse, misuse, respiratory depression, neonatal opioid withdrawal syndrome, and interactions with alcohol and CNS depressants. Concomitant use with CYP3A4 inducers may decrease efficacy, and with CYP2D6 inhibitors may increase toxicity. Risk of serotonin syndrome with serotonergic drugs.
| Common Effects | Constipation |
| Serious Effects |
Hypersensitivity to tramadol, acetaminophen, or any component; significant respiratory depression; acute or severe bronchial asthma; suspected gastrointestinal obstruction; concurrent use of MAOIs or within 14 days; severe hepatic impairment; acetaminophen overdose history.
| Precautions | Addiction, abuse, misuse; life-threatening respiratory depression; neonatal opioid withdrawal syndrome; risks from concomitant use with benzodiazepines or CNS depressants; serotonin syndrome; seizures; suicidal tendencies; adrenal insufficiency; severe hypotension; hepatotoxicity (acetaminophen); anaphylaxis; gastrointestinal obstruction; increased intracranial pressure; impaired renal or hepatic function; use in elderly, cachectic, or debilitated patients. |
Loading safety data…
| First trimester: Limited data; no clear increase in major malformations from acetaminophen; tramadol crosses placenta, animal studies show increased resorptions and skeletal variations. Second and third trimesters: Acetaminophen considered safe; tramadol may cause fetal opioid dependence and neonatal withdrawal syndrome with chronic use. Avoid prolonged use near term due to risk of neonatal respiratory depression. |
| Fetal Monitoring | Monitor maternal pain control, respiratory function, sedation, and signs of tramadol toxicity (CNS depression, seizures). In fetus/neonate: heart rate monitoring if used near delivery; observe for neonatal opioid withdrawal syndrome (irritability, tremor, poor feeding, respiratory distress) with prolonged maternal use. Assess liver function with high doses or chronic acetaminophen use. |
| Fertility Effects | Tramadol may reduce sperm count and motility, and alter hormone levels in males (prolactin, testosterone) based on animal studies. Acetaminophen has been associated with altered sperm parameters and increased risk of cryptorchidism in male offspring when used in pregnancy. Data on female fertility are limited. |