Drug interactions between Benadryl and doxylamine
Interactions between your drugs
diphenhydramine ↔ doxylamine
Applies to:Benadryl (diphenhydramine) and doxylamine
MONITOR: Agents with anticholinergic properties (e.g., sedating antihistamines; antispasmodics; neuroleptics; phenothiazines; skeletal muscle relaxants; tricyclic antidepressants; disopyramide) may have additive effects when used in combination. Excessive parasympatholytic effects may result in paralytic ileus, hyperthermia, heat stroke, and the anticholinergic intoxication syndrome. Peripheral symptoms of intoxication commonly include mydriasis, blurred vision, flushed face, fever, dry skin and mucous membranes, tachycardia, urinary retention, and constipation. Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures. Central nervous system-depressant effects may also be additively or synergistically increased when these agents are combined, especially in elderly or debilitated patients. Use of neuroleptics in combination with other neuroleptics or anticholinergic agents may increase the risk of tardive dyskinesia. In addition, some neuroleptics and tricyclic antidepressants may cause prolongation of the QT interval and theoretically, concurrent use of two or more drugs that can cause QT interval prolongation may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death.
MANAGEMENT: Caution is advised when agents with anticholinergic properties are combined, particularly in the elderly and those with underlying organic brain disease, who tend to be more sensitive to the central anticholinergic effects of these drugs and in whom toxicity symptoms may be easily overlooked. Patients should be advised to notify their physician promptly if they experience potential symptoms of anticholinergic intoxication such as abdominal pain, fever, heat intolerance, blurred vision, confusion, and/or hallucinations. Ambulatory patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them. A reduction in anticholinergic dosages may be necessary if excessive adverse effects develop.
- Kulik AV, Wilbur R "Delirium and stereotypy from anticholinergic antiparkinson drugs." Prog Neuropsychopharmacol Biol Psychiatry 6 (1982): 75-82
- Hvizdos AJ, Bennett JA, Wells BG, Rappaport KB, Mendel SA "Anticholinergic psychosis in a patient receiving usual doses of haloperidol." Clin Pharm 2 (1983): 174-8
- Cohen MA, Alfonso CA, Mosquera M "Development of urinary retention during treatment with clozapine and meclizine [published erratum appears in Am J Psychiatry 1994 Jun;151(6):952]." Am J Psychiatry 151 (1994): 619-20
- Zelman S, Guillan R "Heat stroke in phenothiazine-treated patients: a report of three fatalities." Am J Psychiatry 126 (1970): 1787-90
- Mann SC, Boger WP "Psychotropic drugs, summer heat and humidity, and hyperplexia: a danger restated." Am J Psychiatry 135 (1978): 1097-100
- "Product Information. Artane (trihexyphenidyl)." Lederle Laboratories, Wayne, NJ.
- Johnson AL, Hollister LE, Berger PA "The anticholinergic intoxication syndrome: diagnosis and treatment." J Clin Psychiatry 42 (1981): 313-7
- Forester D "Fatal drug-induced heat stroke." JACEP 7 (1978): 243-4
- Stadnyk AN, Glezos JD "Drug-induced heat stroke." Can Med Assoc J 128 (1983): 957-9
- "Product Information. Cogentin (benztropine)." Merck & Co, Inc, West Point, PA.
- Moreau A, Jones BD, Banno V "Chronic central anticholinergic toxicity in manic depressive illness mimicking dementia." Can J Psychiatry 31 (1986): 339-41
- Warnes H, Lehmann HE, Ban TA "Adynamic ileus during psychoactive medication: a report of three fatal and five severe cases." Can Med Assoc J 96 (1967): 1112-3
- Gershon S, Neubauer H, Sundland DM "Interaction between some anticholinergic agents and phenothiazines." Clin Pharmacol Ther 6 (1965): 749-56
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Drug and food interactions
Applies to: doxylamine
GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.
MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.
- Warrington SJ, Ankier SI, Turner P "Evaluation of possible interactions between ethanol and trazodone or amitriptyline." Neuropsychobiology 15 (1986): 31-7
- Gilman AG, Rall TW, Nies AS, Taylor P, eds. "Goodman and Gilman's the Pharmacological Basis of Therapeutics. 8th ed." New York, NY: Pergamon Press Inc. (1990):
- "Product Information. Fycompa (perampanel)." Eisai Inc, Teaneck, NJ.
- "Product Information. Rexulti (brexpiprazole)." Otsuka American Pharmaceuticals Inc, Rockville, MD.
Therapeutic duplication warnings
Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.
The recommended maximum number of medicines in the 'antihistamines' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'antihistamines' category:
- diphenhydramine (active ingredient in Benadryl (diphenhydramine))
Note: The benefits of taking this combination of medicines may outweigh any risks associated with therapeutic duplication. This information does not take the place of talking to your doctor. Always check with your healthcare provider to determine if any adjustments to your medications are needed.
Drug Interaction Classification
|Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.|
|Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.|
|Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.|
|No information available.|
Do not stop taking any medications without consulting your healthcare provider.
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