MEPERIDINE AND ATROPINE SULFATE
Clinical safety rating: avoid
MAOIs can cause serotonin syndrome and hyperpyrexia Life-threatening respiratory depression may occur.
Meperidine is a synthetic opioid agonist primarily at mu-opioid receptors, producing analgesia; atropine is a competitive antagonist of muscarinic acetylcholine receptors, reducing gastrointestinal motility and secretions.
| Metabolism | Meperidine is primarily metabolized by hepatic CYP3A4 and to a lesser extent CYP2B6 and CYP2C19, producing normeperidine (active metabolite) via N-demethylation; atropine is metabolized by hepatic hydrolysis. |
| Excretion | Meperidine: Renal excretion of unchanged drug (~5-10%) and metabolites, primarily normeperidine (active), with <5% biliary/fecal. Atropine: Renal excretion (~30-50% unchanged), remainder as metabolites, minimal biliary/fecal. |
| Half-life | Meperidine: Terminal half-life 3-4 hours (normal renal function), prolonged in hepatic disease (up to 7-10 hours) and renal impairment (normeperidine accumulates). Atropine: Terminal half-life 2-4 hours. |
| Protein binding | Meperidine: 60-80% bound to albumin and alpha-1-acid glycoprotein. Atropine: 18-50% bound to albumin. |
| Volume of Distribution | Meperidine: Vd 3-5 L/kg (wide tissue distribution, crosses placenta). Atropine: Vd 2-4 L/kg. |
| Bioavailability | Oral meperidine: ~50-60% (first-pass effect). Atropine: Oral bioavailability ~50% (variable). IM/IV: 100%. |
| Onset of Action | IM: 10-15 minutes; IV: 1-2 minutes; SC: 10-15 minutes; Oral: 30-60 minutes. |
| Duration of Action | Analgesic effect: 2-4 hours (IM/IV). Anticholinergic effects (atropine): 4-6 hours. Note: Normeperidine accumulation may prolong CNS effects. |
1-2 mL (meperidine 50 mg/mL + atropine 0.4 mg/mL) IM or IV push (over 2-3 minutes) every 3-4 hours as needed.
| Dosage form | INJECTABLE |
| Renal impairment | GFR 10-50 mL/min: reduce meperidine dose by 25% and extend interval to every 6 hours. GFR <10 mL/min: avoid meperidine (risk of normeperidine accumulation). Atropine: no adjustment. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce meperidine dose by 50%. Child-Pugh C: avoid meperidine (decreased clearance). Atropine: use with caution in severe hepatic impairment. |
| Pediatric use | Meperidine: 1-1.5 mg/kg IM/IV every 3-4 hours (max 100 mg per dose). Atropine: 0.01-0.02 mg/kg IM/IV (max 0.4 mg per dose). For combination, adjust each component accordingly. |
| Geriatric use | Reduce meperidine dose by 25-50% (max 50 mg per dose), extend interval to every 4-6 hours due to increased sensitivity and risk of CNS effects. Atropine: use with caution; lower initial doses recommended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
MAOIs can cause serotonin syndrome and hyperpyrexia Life-threatening respiratory depression may occur.
| FDA category | Positive |
| Breastfeeding | Meperidine: Excreted into breast milk; M/P ratio approximately 0.4–0.8; relative infant dose 1.6–3.8% of maternal weight-adjusted dose. Atropine: Excreted into breast milk in small amounts; M/P ratio unknown. Generally compatible with breastfeeding but monitor infant for sedation, respiratory depression (meperidine) and anticholinergic effects (atropine). |
| Teratogenic Risk |
■ FDA Black Box Warning
Meperidine carries a risk of respiratory depression, addiction, abuse, and misuse; concurrent use with benzodiazepines or CNS depressants may lead to profound sedation, respiratory depression, coma, and death.
| Common Effects | Sedation |
| Serious Effects |
Hypersensitivity to meperidine, atropine, or any component; concomitant or recent MAOI use; severe respiratory insufficiency; acute or severe bronchial asthma; gastrointestinal obstruction; myasthenia gravis; paralytic ileus.
| Precautions | Respiratory depression; hypotension; CNS depression; risk of serotonin syndrome (meperidine); anticholinergic effects (atropine); tolerance and dependence; normeperidine accumulation in renal impairment increasing seizure risk. |
Loading safety data…
| Meperidine: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Atropine: Crosses placenta; no major teratogenic risk reported. First trimester: Avoid unless necessary due to limited safety data. Second and third trimesters: Use only if clearly indicated; may cause neonatal respiratory depression and altered heart rate variability. Risk of maternal respiratory depression and fetal hypoxia with high doses. |
| Fetal Monitoring | Monitor maternal respiratory rate, oxygen saturation, sedation level, and bowel function. Fetal heart rate monitoring for signs of distress or tachycardia (atropine). Neonatal monitoring for respiratory depression, bradycardia, and anticholinergic effects post-delivery. |
| Fertility Effects | No known adverse effects on fertility from either meperidine or atropine. Meperidine may suppress ovulation at high doses due to prolactin inhibition; atropine has no reported fertility impact. |