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Codeine / diphenhydramine / phenylephrine Side Effects

For the Consumer

Applies to codeine / diphenhydramine / phenylephrine: solution, syrup

Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, or throat; excitability; headache; loss of appetite; nausea; nervousness or anxiety; trouble sleeping; upset stomach; vomiting; weakness.

Seek medical attention right away if any of these SEVERE side effects occur while taking codeine / diphenhydramine / phenylephrine:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); confusion; difficulty urinating or inability to urinate; fast or irregular heartbeat; hallucinations; mental or mood changes (eg, irritability); persistent trouble sleeping; restlessness; seizures; severe dizziness, lightheadedness, or headache; severe drowsiness; tremor; vision changes or blurred vision.

For Healthcare Professionals

Applies to codeine / diphenhydramine / phenylephrine: oral syrup

Nervous system

Nervous system side effects have included drowsiness, dizziness, headache, nervousness, restlessness, impairment of mental performance, weakness, mental clouding, lethargy, anxiety, convulsions, CNS depression, tremor, and insomnia.[Ref]


Psychiatric side effects have included fear, dysphoria, psychic dependence, feeling of well-being, confusion, and mood changes.[Ref]


Cardiovascular side effects have included tachycardia, palpitations, arrhythmias, change in heart rate, and cardiovascular collapse with hypotension.[Ref]


Gastrointestinal side effects have included loss of appetite, nausea, constipation, dry mouth, anorexia, vomiting, and heartburn.[Ref]


Genitourinary side effects have included dysuria, polyuria, ureteral spasm, spasm of vesical sphincters, urinary disturbances, and urinary retention.[Ref]


Respiratory side effects have included respiratory difficulty and respiratory depression.[Ref]


Dermatologic side effects have included increased sweating, pallor, skin hash, hives, swelling of face, and dermatitis.[Ref]


Ocular side effects have included blurring of vision and visual disturbances.[Ref]


1. "Product Information. Endal CD (codeine / diphenhydramine / phenylephrine)." Tiber Laboratories, Suwanee, GA.

Not all side effects for codeine / diphenhydramine / phenylephrine 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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