Entre-S Side Effects
Generic Name: chlorpheniramine / dextromethorphan / pseudoephedrine
Note: This page contains information about the side effects of chlorpheniramine / dextromethorphan / pseudoephedrine. Some of the dosage forms included on this document may not apply to the brand name Entre-S.
For the Consumer
Applies to chlorpheniramine / dextromethorphan / pseudoephedrine: tablets
Check with your doctor if any of these most COMMON side effects persist or become bothersome:
Seek medical attention right away if any of these SEVERE side effects occur while taking chlorpheniramine / dextromethorphan / pseudoephedrine:
Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, or throat; excitability; headache; increased sweating; loss of appetite; nausea; nervousness or anxiety; trouble sleeping; upset stomach; vomiting; weakness.
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest tightness; clumsiness or unsteadiness; difficulty urinating or inability to urinate; fast or irregular heartbeat; fever, chills, or sore throat; flushing or redness of the face; hallucinations; mental or mood changes; numbness or tingling; seizures; severe dizziness, drowsiness, lightheadedness, or headache; severe dryness of mouth, nose, and throat; severe or persistent trouble sleeping; shortness of breath; tremor; unusual bruising or bleeding; vision problems (eg, double vision, severe or persistent blurred vision).
For Healthcare Professionals
Applies to chlorpheniramine / dextromethorphan / pseudoephedrine: oral liquid, oral suspension extended release, oral tablet chewable
Nearly all patients treated with chlorpheniramine experience drowsiness. This drowsiness may subside in some patients with extended use.
Few cases of dyskinesias and tremors, often of the face, have been reported in patients whose chronic use of chlorpheniramine extended over a period of 3 to 10 years. Some of these cases were only partially relieved by discontinuation of the drug. Haloperidol was successful in relieving symptoms.[Ref]
Nervous system side effects of chlorpheniramine have included drowsiness in 75% or more of treated patients. Dyskinesias have rarely been reported following chronic use of chlorpheniramine.
Nervous system side effects of dextromethorphan have included drowsiness and dizziness. Other side effects such as excitation, mental confusion, and opioid like respiratory depression have been rare and occurred at higher dosages. In some cases of abuse, patients experienced euphoria, hyperactivity, mania, and auditory and visual hallucinations.
Nervous system side effects of pseudoephedrine have included insomnia in up to 30% of patients. Tremor, anxiety, nervousness, and headache have also been reported.[Ref]
Gastrointestinal side effects of chlorpheniramine have included dry mouth and constipation in up to one-third of treated patients.
Gastrointestinal side effects of dextromethorphan have included stomach upset.
Gastrointestinal side effects of pseudoephedrine have included anorexia and gastric irritation in approximately 5% of patients. Dry mouth, nose, or throat have occurred in up to 15% of patients.[Ref]
Pseudoephedrine causes vasoconstriction which generally does not produce hypertension, but may be problematic for patients with preexisting hypertension. Arrhythmias may be produced in predisposed patients. Rarely, pseudoephedrine has been reported to cause coronary artery spasm and chest pain.
One report evaluated the effect with 60 mg of pseudoephedrine on individuals in a hyperbaric chamber at 1 atmosphere (simulated scuba dive to 66 feet of sea water). Pseudoephedrine and depth (simulated) were found to have significant but opposite effects on heart rate, although these effects were unlikely to be clinically significant during diving.[Ref]
Cardiovascular side effects of chlorpheniramine have included hypotension, tachycardia, and palpitations.
Cardiovascular side effects of pseudoephedrine have included tachycardia. Some patients have developed hypertension and/or arrhythmias.[Ref]
Ocular effects of chlorpheniramine have included blurred vision, diplopia, and dry eyes due to anticholinergic effects.[Ref]
Genitourinary side effects of chlorpheniramine have included dysuria, urinary hesitancy, and a decreased urine flow. In rare cases, the anticholinergic effect of chlorpheniramine has precipitated acute urinary retention.[Ref]
Hematologic side effects of chlorpheniramine have included bone marrow suppression, thrombocytopenia, and aplastic anemia.[Ref]
A fatal case of agranulocytosis has been reported in a patient taking chlorpheniramine, pseudoephedrine, acetaminophen, dextromethorphan, phenylpropanolamine, and aspirin. Chlorpheniramine was felt to be the cause.[Ref]
Hypersensitivity side effects of dextromethorphan have included rare reports of fixed-drug eruptions.
Hypersensitivity side effects of pseudoephedrine have included fixed-drug eruptions.[Ref]
1. Lyon CC, Turney JH "Pseudoephedrine toxicity in renal failure." Br J Clin Pract 50 (1996): 396-7
2. Bantz EW, Dolen WK, Chadwick EW, Nelson HS "Chronic chlorpheniramine therapy: subsensitivity, drug metabolism, and compliance." Ann Allergy 59 (1987): 341-6
3. Bostwick JM "Dextromethorphan-induced manic symptoms in a bipolar patient on lithium." Psychosomatics 37 (1996): 571-2
4. Polles A, Griffith JL "Dextromethorphan-induced mania." Psychosomatics 37 (1996): 71-4
5. Krause LB, Shuster S "A comparison of astemizole and chlorpheniramine in dermographic urticaria." Br J Dermatol 112 (1985): 447-53
6. Schuller DE, Turkewitz D "Adverse effects of antihistamines." Postgrad Med 79 (1986): 75-86
7. Dowd J, Bailey D, Moussa K, Nair S, Doyle R, CulpepperMorgan JA "Ischemic colitis associated with pseudoephedrine: Four cases." Am J Gastroenterol 94 (1999): 2430-4
8. Taylor DM, O'Toole KS, Auble TE, Ryan CM, Sherman DR "The psychometric and cardiac effects of pseudoephedrine in the hyperbaric environment." Pharmacotherapy 20 (2000): 1045-50
9. "Product Information. Chlortrimeton (chlorpheniramine)." Schering-Plough, Liberty Corner, NJ.
10. Gill ND, Shield A, Blazevich AJ, Zhou S, Weatherby RP "Muscular and cardiorespiratory effects of pseudoephedrine in human athletes." Br J Clin Pharmacol 50 (2000): 205-13
11. Vidal C, Prieto A, PerezCarral C, Armisen M "Nonpigmenting fixed drug eruption due to pseudoephedrine." Ann Allergy Asthma Immunol 80 (1998): 309-10
12. Knowles SR, Weber E "Dextromethorphan anaphylaxis." J Allerg Clin Immunol 102 (1998): 316-7
Not all side effects for Entre-S may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.
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