Scopolamine Interactions
- Amantadine
- Amoxapine
Antacids
Antimuscarinics
Anxiolytics, Sedatives, and Hypnotics
- Atomoxetine
- Bupropion
- Cisapride
- Clozapine
- Cyclobenzaprine
- Digoxin
- Disopyramide
- Erythromycin
- Ethanol
- Ketoconazole
- Maprotiline
- Memantine
- Metoclopramide
- Olanzapine
Opiate agonists
- Orphenadrine
Parasympathomimetics
Phenothiazines
- Potassium Salts
- Quinidine
Sedating H1-blockers
- Tegaserod
- Topiramate
Tricyclic antidepressants
Scopolamine Interactions
Additive anticholinergic effects may be seen when scopolamine is used concomitantly with other antimuscarinics. Other commonly used drugs with moderate to significant anticholinergic effects include amantadine, amoxapine, bupropion, clozapine, cyclobenzaprine, disopyramide, maprotiline, olanzapine, orphenadrine, the sedating H1-blockers, most phenothiazines, and most tricyclic antidepressants. Clinicians should note that antimuscarinic effects might be seen not only on GI smooth muscle, but also on bladder function, the eye, and temperature regulation. With many of the listed agents, additive drowsiness may also occur when combined with scopolamine.
Scopolamine may cause dizziness and drowsiness. Concurrent use of scopolamine and CNS depressants (such as ethanol, anxiolytics, sedatives, and hypnotics) can adversely increase the risk of CNS depression.
Opiate agonists should be used cautiously with antimuscarinics since additive depressive effects on GI motility or bladder function may been seen. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. Opiate analgesics combined with antimuscarinics can cause severe constipation or paralytic ileus, especially with chronic use. Additive drowsiness with scopolamine may also occur. Pharmacology texts report that meperidine exerts less pronounced effects on GI smooth muscle than other opiate agonists.
Oral formulations of digoxin can produce higher serum concentrations when administered concurrently with antimuscarinics (e.g., propantheline) because of decreased GI motility induced by the antimuscarinic agent. This interaction has mostly occurred in the literature with slowly-dissolving, large-particle formulations of digoxin tablets; the manufacture of oral digoxin products today, utilizing liquid formulations and/or smaller particle sizes, theoretically reduces the potential for absorption interactions. However, there is wide variability expected in individual responses to many digoxin-drug interactions. Other pharmacodynamic and pharmacokinetic systemic interactions are possible between digoxin and select antimuscarinic agents. Anticholinergics, because of their ability to cause tachycardia, can also antagonize the beneficial actions of digoxin in atrial fibrillation/flutter. Routine therapeutic monitoring should be continued when an antimuscarinic agent is prescribed with digoxin until the effects of combined use are known.
The reduction in GI motility produced by scopolamine may increase the absorption of some drugs, including quinidine. Increased monitoring is advised in patients receiving this combination.
Drugs that decrease GI motility may increase the risk of GI irritation from sustained-release solid oral dosage forms of potassium salts. Examples of drugs that significantly decrease GI motility include the antimuscarinics.
Ketoconazole requires an acidic pH for oral absorption. Medications that increase gastric pH or decrease acid output can cause a notable decrease in the bioavailability of ketoconazole. Medications that have this effect include antimuscarinics. Antimuscarinics have a prolonged duration of action, and staggering their time of administration with ketoconazole by several hours may not prevent the drug interaction. An alternative imidazole antifungal should be considered if antimuscarinic medications are required.
Because scopolamine exhibits antimuscarinic properties that may slow GI motility, use with caution in patients receiving cisapride, erythromycin (when erythromycin is being administered to enhance GI motility), metoclopramide, or tegaserod. Avoid chronic administration of antimuscarinics along with prokinetic agents under most circumstances. The clinical significance of these potential interactions is uncertain. This interaction is less likely with ophthalmic scopolamine, unless significant systemic absorption of scopolamine occurs.
The muscarinic actions of drugs known as parasympathomimetics, including both direct cholinergic receptor agonists and cholinesterase inhibitors, can antagonize the antimuscarinic actions of scopolamine.
Through an additive effect, the use of topiramate (a weak carbonic anhydrase inhibitor) with agents that may increase the risk for heat-related disorders, such as antimuscarinics, may lead to oligohidrosis, hyperthermia and/or heat stroke.
Antacids may inhibit the oral absorption of scopolamine and other antimuscarinics. Simultaneous oral administration should be avoided when feasible; separate dosing by at least 2 hours to limit an interaction.
Scopolamine and atomoxetine should be combined cautiously in patients with known cardiac disease. Scopolamine may alter the heart rate; the predominant clinical effect is sinus tachycardia. An additive effect on heart rate may occur as atomoxetine may elevate heart rate as well as blood pressure.
The adverse effects of antimuscarinics, such as dry mouth, urinary hesitancy or blurred vision may be enhanced with use of memantine; dosage adjustments of the anticholinergic drug may be required when memantine is coadministered.
[ Last revised: 4/6/2006 2:02:00 PM ]
References
. Ben-Zeev B, Watemberg N, Augarten A, et al. Oligohydrosis and hyperthermia: a pilot study of a novel topiramate adverse effect. J Child Neurol 2003;18:254 - 7.
. Ketoconazole package insert. Schaumburg, IL: Novopharm USA Inc.; 1997 Oct.
. Quinidex Extentabs® (quinidine sulfate extended-release tablets) package insert. Richmond, VA: A.H. Robbins Company; 2000 Sept.
. Lanoxin® (digoxin) package insert. Research Triangle Park, NC: Glaxo Smith Kline; 2001 Aug.
. Strattera® (atomoxetine) package insert. Indianapolis, IN: Eli Lilly and Company; 2003 Sept.
. Amoxapine package insert. Corona, CA: Watson Laboratories, Inc.; 2002 Mar.
. Ludiomil® (maprotiline) package insert. Stein, Switzerland: Novartis Pharma Stein AG; 1997 Apr.
. Reglan® (metoclopramide) package insert. Milwaukee, WI: Schwarz Pharma; 2004 Feb.
. Zelnorm® (tegaserod maleate) package insert. East Hanover, NJ: Novartis Pharmaceuticals Corporation; 2004 April.
. Sutherland SE, Goldman HB. Treatment options for female urinary incontinence. Med Clin North Am 2004;88:345 - 66.
. Chieppa DM, Mansi G, Rinaldi M, et al. Effects of erythromycin on human colonic circular muscle in idiopathic chronic constipation. Eur J Clin Invest 2000;30:66 - 71.
. Food and Drug Administration (FDA). NDA Safety Review: NDA 21-487, Memantine, Forest Laboratories, Inc.;August 20, 2003. Retrieved July 12, 2004. Available on the World Wide Web at http://www.fda.gov/ohrms/dockets/ac/03/briefing/3979B1_04_FDA-Safety%20Review.pdf.
. Hoffman BB, Lefkowitz RJ. Atropine, scopolamine, and related antimuscarinic drugs. Gilman AG, Rall TW, Nies AS, Taylor P, (eds.) In: Goodman and Gilman’s Pharmacological Basis of Therapeutics. 8th ed., New York, Pergamon Press. 1990. 150 - 61.
. Duragesic® (fentanyl transdermal system) package insert. Titusville, NJ: Janssen Pharmaceutica Products, L.P.; 2003 Jan.
. Topamax® (topiramate) package insert. Raritan, NJ: Ortho-McNeil Pharmaceutical, Inc.; 2004 Aug.
. Brown JH, Taylor P. Muscarinic receptor agonists and antagonists. In: Hardman JG, Limbird LE, Molinoff PB, Ruddon RW, Gilman AG, eds. Goodman and Gilman’s the pharmacological basis of therapeutics, 9th edn. New York: McGraw Hill, 1996;141 - 160.
. Potassium Chloride Extended-release Tablets package insert. Fort Lauderdale, FL: Andrx Pharmaceutials Inc.; 2001 Apr.
. Bedford TA, Rowbotham DJ. Cisapride. Drug interactions of clinical significance. Drug Saf. 1996;15:167 - 75.
. Transderm Scop® (transdermal scopolamine) package insert. Parsippany, NJ: Novartis Consumer Health; 2004 June.
. Pamine®/Pamine® Forte (methscopolamine bromide) package insert. Fairfield, NJ: Kenwood Therapeutics.; 2003 Jul.
. Lanoxicaps® (digoxin solution in capsules) package insert. Research Triangle Park, NC: GlaxoSmithKline; 2003 Oct.
Related entries
Syndicate
|
