ATROPINE AND DEMEROL
Clinical safety rating
cautionComprehensive clinical and safety monograph for ATROPINE AND DEMEROL (ATROPINE AND DEMEROL).
Atropine is an antimuscarinic agent that competitively blocks acetylcholine at muscarinic receptors, reducing secretions and gastrointestinal motility. Meperidine (Demerol) is an opioid agonist that binds to mu-opioid receptors in the CNS, altering pain perception and producing analgesia.
| Metabolism | Meperidine is primarily metabolized in the liver via hydrolysis to meperidinic acid and via N-demethylation to normeperidine (active metabolite), involving CYP3A4 and CYP2B6. Atropine is metabolized in the liver via hydrolysis and glucuronidation; approximately 50% is excreted unchanged in urine. |
| Excretion | Atropine: approximately 50% excreted unchanged in urine, remainder as metabolites (biliary and renal). Demerol (meperidine): primarily hepatic metabolism; <5% excreted unchanged in urine; metabolites (including normeperidine) excreted renally. |
| Half-life | Atropine: 2-4 hours (terminal half-life). Demerol: 2.5-4 hours; normeperidine metabolite half-life 15-30 hours (accumulates in renal impairment). |
| Protein binding | Atropine: ~44% bound to albumin and alpha-1 acid glycoprotein. Demerol: ~60% bound to albumin and alpha-1 acid glycoprotein. |
| Volume of Distribution | Atropine: 1-3 L/kg (large, extensive tissue distribution). Demerol: 3-5 L/kg (large, distributes widely including CNS). |
| Bioavailability | Atropine: oral ~10-25% (extensive first-pass metabolism). Demerol: oral ~50-60% (significant first-pass metabolism). IM/IV 100%. |
| Onset of Action | Atropine: IV ~1-2 min, IM ~5-10 min, oral ~30-60 min. Demerol: IV ~1-5 min, IM ~10-15 min, oral ~20-30 min. |
| Duration of Action | Atropine: anticholinergic effects last 4-6 hours. Demerol: analgesic effects last 2-4 hours (IV/IM), 3-4 hours (oral). |
| Molecular Weight | Atropine: 289.37 Da; Meperidine: 247.33 Da |
Atropine 0.4 mg and Demerol (meperidine) 50-100 mg intramuscularly as preanesthetic medication 30-60 minutes before procedure.
| Dosage form | INJECTABLE |
| Renal impairment | Meperidine: GFR 10-50 mL/min: administer 75% of normal dose; GFR <10 mL/min: administer 50% of normal dose and avoid due to normeperidine accumulation. Atropine: no adjustment required. |
| Liver impairment | Meperidine: Child-Pugh A: reduce dose by 25%; Child-Pugh B: reduce by 50%; Child-Pugh C: contraindicated. Atropine: caution in severe hepatic impairment. |
| Pediatric use | Atropine 0.01 mg/kg (max 0.4 mg) and meperidine 1-2 mg/kg (max 100 mg) intramuscularly 30-60 minutes before procedure. |
| Geriatric use | Reduce meperidine dose by 50% and avoid in elderly due to risk of seizures and delirium; use alternative opioids. Atropine dose unchanged but monitor for anticholinergic effects. |
| 1st trimester | Avoid: Potential teratogenicity; atropine may cause fetal tachycardia; meperidine associated with fetal growth restriction at high doses. |
| 2nd trimester | Caution: Use only if clearly needed; risk of fetal tachycardia and respiratory depression. |
| 3rd trimester | Avoid: Risk of neonatal respiratory depression, withdrawal symptoms (meperidine), and anticholinergic effects (atropine). |
Clinical note
Comprehensive clinical and safety monograph for ATROPINE AND DEMEROL (ATROPINE AND DEMEROL).
| Placental transfer | Both cross placenta readily; meperidine achieves fetal plasma concentrations 70-80% of maternal; atropine crosses quickly, causing fetal tachycardia. |
| Breastfeeding | Both atropine and meperidine are excreted into breast milk; meperidine can accumulate in neonates due to immature metabolism, causing CNS depression; atropine may cause anticholinergic effects; generally not recommended; consider alternative analgesics. |
| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | Atropine: FDA Pregnancy Category C. Crosses placenta; may cause fetal tachycardia. Demerol (meperidine): FDA Pregnancy Category C. First trimester: limited human data; animal studies show no teratogenicity. Second trimester: no specific risks. Third trimester: use near term may cause neonatal respiratory depression, decreased Apgar scores, and withdrawal symptoms. Chronic use may lead to neonatal opioid withdrawal syndrome (NOWS). |
| Fetal Monitoring | Maternal: Heart rate, blood pressure, respiratory rate, oxygen saturation, pain level, sedation score, signs of anticholinergic toxicity (atropine). Fetal: Heart rate monitoring (tocodynamometry) for tachycardia or bradycardia; biophysical profile if used repeatedly. Neonate: Apgar scores, respiratory rate, sedation, feeding ability, assessment for withdrawal symptoms if chronic use. |
| Fertility Effects | Atropine: No known effects on fertility. Demerol: May decrease fertility in males (sperm motility/ count) and females (menstrual irregularities) with chronic use; acute effects unknown. |
■ FDA Black Box Warning
Meperidine has a boxed warning for risk of respiratory depression, especially in elderly, cachectic, or debilitated patients, and when used with CNS depressants. Also, risk of serotonin syndrome when co-administered with serotonergic drugs, and risk of abuse, addiction, and diversion.
| Serious Effects |
Hypersensitivity to atropine, meperidine, or any componentMyasthenia gravis (atropine)Narrow-angle glaucoma (atropine)Severe hepatic or renal impairment (meperidine)Concurrent or recent MAOI use (meperidine)Respiratory depression (meperidine)Acute or severe asthma (meperidine)Suspected surgical abdomen (atropine may obscure signs)
| Precautions | Respiratory depression, hypotension, bradycardia, urinary retention, constipation, serotonin syndrome, seizures (normeperidine accumulation), decreased GI motility, drug dependence, and tolerance. Use caution in elderly, renal impairment, hepatic impairment, respiratory disorders, prostatic hyperplasia, glaucoma, and with concurrent CNS depressants. |
| Food/Dietary | Avoid alcohol. Meperidine may interact with foods containing tyramine (aged cheeses, cured meats) in patients on MAOIs; otherwise no significant food interactions. |
| Clinical Pearls | Atropine and Demerol (meperidine) combination is used for pre-anesthetic medication to reduce secretions and produce sedation. Monitor for CNS depression, respiratory depression, and anticholinergic effects (tachycardia, dry mouth, urinary retention). Use cautiously in elderly, patients with COPD, asthma, or prostatic hyperplasia. Avoid in patients with MAOIs due to risk of serotonin syndrome. |
| Patient Advice | This medication may cause drowsiness, dizziness, or blurred vision; avoid driving or operating machinery until effects are known. · Avoid alcohol and other CNS depressants while taking this medication. · Report difficulty urinating, fast heartbeat, or severe constipation to your healthcare provider. · Do not take more than prescribed; risk of dependence with long-term use. · Keep out of reach of children; may cause serious breathing problems if accidentally taken. |
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