Diphenhydramine / pseudoephedrine Side Effects
For the Consumer
Applies to diphenhydramine / pseudoephedrine: oral tablet
What are some side effects that I need to call my doctor about right away?
WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:
- Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
What are some other side effects of this drug?
All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
- Feeling nervous and excitable.
- Not able to sleep.
- Feeling sleepy.
These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.
You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.
For Healthcare Professionals
The CNS depressant effect of diphenhydramine parallels its plasma concentrations. The plasma concentration threshold for sedation is 30 to 42 ng/mL, and to cause mental impairment is 58 to 74 ng/mL. Patients should be warned against driving while taking diphenhydramine, and should avoid concomitant ingestion of alcohol.
Dystonic reactions to diphenhydramine have been accompanied by dizziness, mental confusion, rigidity, lip and tongue protrusion, trismus, torticollis, and swallowing difficulties. These reactions generally resolve spontaneously. Toxic encephalopathy has been reported in a child with chicken pox treated generously with topical diphenhydramine.
Delirium has been reported in elderly patients with mild dementia following small oral doses of diphenhydramine.[Ref]
Central nervous system (CNS) depression commonly occurs with diphenhydramine administration, resulting in drowsiness and sedation in nearly all patients treated. Motor skills may be impaired. Dystonic reactions have been reported after single doses of diphenhydramine.
Pseudoephedrine produces nervous system stimulation, resulting in tremor, anxiety, and nervousness. Insomnia is reported in up to 30% of pseudoephedrine-treated patients. Headache may also occur in patients receiving pseudoephedrine.[Ref]
Cardiovascular effects of diphenhydramine may include hypotension, tachycardia, and palpitations.
Cardiovascular adverse effects more commonly may be associated with pseudoephedrine. Pseudoephedrine generally causes a significant rise in heart rate. Hypertension and arrhythmias may be problematic in susceptible patients.[Ref]
Pseudoephedrine causes vasoconstriction which generally does not produce hypertension, but may be problematic for patients with pre-existing hypertension. Arrhythmias may be produced in predisposed patients. Rarely, pseudoephedrine has been reported to cause coronary artery spasm and chest pain.[Ref]
Hypersensitivity reactions may occur with diphenhydramine, generally resulting in rash, pruritus and eczema. Photosensitivity reactions have also been reported with diphenhydramine.
Hypersensitivity reactions to pseudoephedrine may also occur. Fixed drug eruptions secondary to pseudoephedrine have been reported.[Ref]
Most commonly, hypersensitivity to diphenhydramine manifests itself in patients receiving systemic drug after being sensitized to it by topical application. Sensitization with systemic administration has also been reported.[Ref]
Gastrointestinal tract adverse effects of diphenhydramine are mild, and may include nausea, dry mouth, and constipation.
Gastrointestinal adverse effects of pseudoephedrine may include anorexia and gastric irritation in approximately 5% of patients. Dry mouth, nose, or throat may occur in up to 15% of patients.[Ref]
Ocular affects of diphenhydramine may include blurred vision, diplopia, and dry eyes due to its anticholinergic effect.[Ref]
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17. Gordon RD, Ballantine DM, Bachmann AW "Effects of repeated doses of pseudoephedrine on blood pressure and plasma catecholamines in normal subjects and in patients with phaeochromocytoma." Clin Exp Pharmacol Physiol 19 (1992): 287-90
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Some side effects of diphenhydramine / pseudoephedrine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
More about diphenhydramine/pseudoephedrine
- Side Effects
- During Pregnancy
- Drug Interactions
- Support Group
- 1 Review – Add your own review/rating
- Drug class: upper respiratory combinations
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