Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ANAFRANIL vs ATROPINE AND DEMEROL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Clomipramine is a tricyclic antidepressant (TCA) that inhibits the reuptake of serotonin and norepinephrine, with a higher potency for serotonin reuptake inhibition. It also has anticholinergic, antihistaminergic, and alpha-adrenergic blocking properties.
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.
Obsessive-compulsive disorder (OCD),Off-label: depression, panic disorder, chronic pain, cataplexy associated with narcolepsy, premature ejaculation
Preanesthetic medication to reduce secretions and prevent bradycardia,Management of moderate to severe pain (as an opioid analgesic),Off-label: treatment of opioid-induced constipation (meperidine component)
Initial: 25 mg PO tid; increase gradually to 100-150 mg/day. Maximum: 250 mg/day. Maintenance: lowest effective dose.
Atropine 0.4 mg and Demerol (meperidine) 50-100 mg intramuscularly as preanesthetic medication 30-60 minutes before procedure.
Terminal elimination half-life of clomipramine is approximately 21-26 hours; its active metabolite, desmethylclomipramine, has a half-life of approximately 36-42 hours. Steady-state is achieved within 7-14 days.
Atropine: 2-4 hours (terminal half-life). Demerol: 2.5-4 hours; normeperidine metabolite half-life 15-30 hours (accumulates in renal impairment).
Primarily hepatic via CYP1A2, CYP3A4, CYP2C19, and CYP2D6; active metabolite desmethylclomipramine formed via N-demethylation.
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.
Renal (primarily as conjugated metabolites, ~60-70% over 72 hours); fecal (biliary excretion of ~10-20%); <2% excreted unchanged in urine.
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.
97.6% bound primarily to alpha1-acid glycoprotein and albumin.
Atropine: ~44% bound to albumin and alpha-1 acid glycoprotein. Demerol: ~60% bound to albumin and alpha-1 acid glycoprotein.
Approximately 12-17 L/kg, indicating extensive tissue distribution.
Atropine: 1-3 L/kg (large, extensive tissue distribution). Demerol: 3-5 L/kg (large, distributes widely including CNS).
Oral bioavailability is approximately 45-55% due to first-pass metabolism. IV administration yields 100%.
Atropine: oral ~10-25% (extensive first-pass metabolism). Demerol: oral ~50-60% (significant first-pass metabolism). IM/IV 100%.
No specific guidelines. Use with caution in severe renal impairment (Cr Cl <30 m L/min); consider dose reduction based on tolerability.
Meperidine: GFR 10-50 m L/min: administer 75% of normal dose; GFR <10 m L/min: administer 50% of normal dose and avoid due to normeperidine accumulation. Atropine: no adjustment required.
Child-Pugh A: no adjustment needed. Child-Pugh B: reduce dose by 50%. Child-Pugh C: contraindicated.
Meperidine: Child-Pugh A: reduce dose by 25%; Child-Pugh B: reduce by 50%; Child-Pugh C: contraindicated. Atropine: caution in severe hepatic impairment.
Not recommended for children <10 years. For adolescents: initial 25 mg PO daily, increase slowly to 3 mg/kg/day or 100 mg/day maximum (whichever is lower).
Atropine 0.01 mg/kg (max 0.4 mg) and meperidine 1-2 mg/kg (max 100 mg) intramuscularly 30-60 minutes before procedure.
Initial: 10 mg PO daily; increase slowly to 30-50 mg/day. Monitor for orthostatic hypotension, sedation, and anticholinergic effects.
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.
Suicidality and Antidepressant Drugs: Antidepressants increased the risk of suicidal thinking and behavior in children, adolescents, and young adults in short-term studies. Closely monitor for clinical worsening, suicidality, or unusual changes in behavior.
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.
May increase risk of suicidal thoughts/behaviors; serotonin syndrome when used with other serotonergic drugs; lowering of seizure threshold; orthostatic hypotension; anticholinergic effects (e.g., urinary retention, blurred vision); cardiac conduction abnormalities; QT prolongation; neuroleptic malignant syndrome; angle-closure glaucoma; hyperpyrexia; withdrawal symptoms upon abrupt discontinuation; use with caution in patients with cardiovascular disease, hepatic impairment, renal impairment, history of seizures, and elderly patients.
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.
Hypersensitivity to clomipramine or other tricyclics; concurrent use or within 14 days of MAO inhibitors; recent myocardial infarction; history of seizure disorder; narrow-angle glaucoma; urinary retention; concurrent use with linezolid or methylene blue.
Hypersensitivity to atropine or meperidine; severe asthma or COPD; acute respiratory depression; paralytic ileus; known or suspected gastrointestinal obstruction; patients receiving MAOIs (within 14 days); myasthenia gravis (relative for atropine); increased intraocular pressure (glaucoma); severe renal impairment (normeperidine accumulation).
Avoid grapefruit and grapefruit juice as they may increase clomipramine levels. Take with food to reduce gastric upset. Avoid excessive caffeine; it may increase side effects like anxiety or tremors. Limit alcohol due to additive CNS depression.
Avoid alcohol. Meperidine may interact with foods containing tyramine (aged cheeses, cured meats) in patients on MAOIs; otherwise no significant food interactions.
First trimester: Limited data; possible increased risk of congenital heart defects (RR ~1.3). Second/third trimester: Risk of neonatal withdrawal syndrome (jitteriness, feeding difficulties, respiratory distress) and persistent pulmonary hypertension of the newborn (PPHN) with late exposure.
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).
Anafranil (clomipramine) is excreted into breast milk. M/P ratio approximately 0.5-1.0. Relative infant dose estimated 1-2% of maternal weight-adjusted dose. Monitor infant for drowsiness, feeding difficulties, and weight loss. Generally compatible with caution.
Atropine: Excreted in breast milk in small amounts; may inhibit lactation. M/P ratio not established. Use with caution; monitor infant for anticholinergic effects (tachycardia, dry mouth). Demerol: Excreted in breast milk; relative infant dose (RID) ~0.5-0.8% of maternal weight-adjusted dose. M/P ratio 1.0-1.6. Limited data; avoid in breastfeeding due to potential neonatal sedation and respiratory depression. American Academy of Pediatrics considers meperidine compatible but caution advised.
Due to increased plasma volume and enhanced hepatic metabolism in pregnancy, serum levels may decrease by up to 50%. Consider dose adjustment based on clinical response and trough levels; typical increase by 25-50% may be needed in later pregnancy. Postpartum, reduce dose to prepregnancy levels over 1-2 weeks.
Atropine: No specific dose adjustments recommended; increased volume of distribution may require higher doses for effect. Demerol: Increased clearance and volume of distribution in pregnancy; standard doses may be less effective. Avoid use during labor due to risk of neonatal respiratory depression; if necessary, use lowest effective dose and monitor neonate. No specific dose reduction recommended, but caution with repeated doses.
Anafranil (clomipramine) is a tricyclic antidepressant (TCA) primarily used for obsessive-compulsive disorder (OCD). Monitor for QT prolongation, especially in patients with cardiac risk factors or on other QT-prolonging drugs. Due to anticholinergic effects, use cautiously in elderly, those with BPH, or narrow-angle glaucoma. Start low and titrate slowly to minimize side effects. Therapeutic response may take 2-4 weeks. Do not discontinue abruptly due to withdrawal symptoms.
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.
Take exactly as prescribed; do not adjust dose without consulting your doctor.,It may take several weeks to feel the full benefit; do not stop suddenly.,Avoid alcohol and other CNS depressants.,Report any suicidal thoughts, worsening depression, or mood changes immediately.,May cause drowsiness, dizziness, or blurred vision; avoid driving until you know how it affects you.,Dry mouth, constipation, and urinary retention are common; increase fluid intake and dietary fiber.,Use sun protection; this medication can increase sensitivity to sunlight.,Do not take with MAO inhibitors (e.g., linezolid, methylene blue) or within 14 days of stopping them.
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.
No interactions on record
"Rivastigmine, a reversible carbamate acetylcholinesterase inhibitor, increases synaptic acetylcholine levels, enhancing cholinergic transmission. Atropine, a competitive antagonist of muscarinic acetylcholine receptors, blocks the effects of acetylcholine at these receptors, leading to reduced parasympathetic activity. When used together, atropine can diminish the therapeutic efficacy of rivastigmine by pharmacodynamically antagonizing its cholinergic effects, particularly in the central nervous system and peripheral muscarinic receptors, potentially worsening cognitive function in Alzheimer's disease patients."
"Umeclidinium, a long-acting muscarinic antagonist (LAMA), and atropine, a non-selective muscarinic antagonist, both block the action of acetylcholine at muscarinic receptors in the parasympathetic nervous system. Their co-administration leads to additive anticholinergic effects, resulting in an increased risk of peripheral anticholinergic adverse effects such as dry mouth, blurred vision, constipation, urinary retention, and tachycardia, as well as central nervous system effects like confusion or delirium, especially in elderly patients. Clinically, this combination may also exacerbate conditions such as angle-closure glaucoma or paralytic ileus."
"Concurrent use of atropine and gallamine triethiodide results in additive antagonism at muscarinic acetylcholine receptors, leading to enhanced blockade of parasympathetic effects and increased risk of tachycardia, hypertension, and delirium. Atropine, a competitive antagonist of muscarinic receptors, counteracts the vagolytic effects of gallamine, a nondepolarizing neuromuscular blocker that also exhibits weak vagolytic activity. This pharmacodynamic interaction can cause severe sinus tachycardia, hypertension, and central anticholinergic syndrome, especially in elderly patients or those with cardiovascular disease."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ANAFRANIL vs ATROPINE AND DEMEROL, answered by our medical review team.
ANAFRANIL is a Tricyclic Antidepressant that works by Clomipramine is a tricyclic antidepressant (TCA) that inhibits the reuptake of serotonin and norepinephrine, with a higher potency for serotonin reuptake inhibition. It also has anticholinergic, antihistaminergic, and alpha-adrenergic blocking properties.. ATROPINE AND DEMEROL is a Opioid Analgesic Combination that works by 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ANAFRANIL and ATROPINE AND DEMEROL depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ANAFRANIL is: Initial: 25 mg PO tid; increase gradually to 100-150 mg/day. Maximum: 250 mg/day. Maintenance: lowest effective dose.. The standard adult dose of ATROPINE AND DEMEROL is: Atropine 0.4 mg and Demerol (meperidine) 50-100 mg intramuscularly as preanesthetic medication 30-60 minutes before procedure.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ANAFRANIL and ATROPINE AND DEMEROL in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ANAFRANIL is classified as Category C. First trimester: Limited data; possible increased risk of congenital heart defects (RR ~1.3). Second/third trimester: Risk of neonatal withdrawal syndrome (jitteriness, feeding dif. ATROPINE AND DEMEROL is classified as Category C. Atropine: FDA Pregnancy Category C. Crosses placenta; may cause fetal tachycardia. Demerol (meperidine): FDA Pregnancy Category C. First trimester: limited human data; animal studi. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.