Dextromethorphan / promethazine Side Effects
Some side effects of dextromethorphan / promethazine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
For the Consumer
Applies to dextromethorphan / promethazine: syrup
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 dextromethorphan / promethazine:
Dizziness; drowsiness; dry mouth; nausea; stomach upset.
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision; confusion; fainting; fast or irregular heartbeat; fever, chills, or sore throat; hallucinations; seizures; sensitivity to light; tremor; uncontrolled muscle movements; unusual bruising or bleeding; yellowing of skin or eyes.
For Healthcare Professionals
Applies to dextromethorphan / promethazine: oral syrup
Nervous system side effects have included tinnitus, drowsiness, dizziness, sedation, somnolence, confusion, disorientation, lassitude, incoordination, fatigue, euphoria, nervousness, insomnia, tremors, convulsive seizures, excitation, catatonic-like states, hysteria, hallucinations, and extrapyramidal symptoms such as oculogyric crisis, torticollis, and tongue protrusion
Gastrointestinal side effects have included dry mouth, nausea, vomiting, and gastrointestinal disturbances.
Cardiovascular side effect have included increased or decreased blood pressure, tachycardia, bradycardia, and faintness.
Hepatic side effects have included jaundice.
Hematologic side effects have included leukopenia, thrombocytopenia, thrombocytopenic purpura, and agranulocytosis.
Dermatologic side effects have included dermatitis, photosensitivity, and urticaria.
Respiratory side effects have included asthma, nasal stuffiness, respiratory depression (potentially fatal) and apnea (potentially fatal).
Hypersensitivity side effects ave included angioneurotic edema.
Other side effects have included neuroleptic malignant syndrome (potentially fatal).
A potentially fatal symptom complex sometimes referred to as Neuroleptic Malignant Syndrome (NMS) has been reported in association with promethazine alone or in combination with antipsychotic drugs. Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis and cardiac dysrhythmias). The diagnostic evaluation of patients with this syndrome is complicated. In arriving at a diagnosis, it is important to identify cases where the clinical presentation includes both serious medical illness (e.g., pneumonia, systemic infection, etc.) and untreated or inadequately treated extrapyramidal signs and symptoms (EPS). Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever and primary central nervous system (CNS) pathology.
The management of NMS should include 1) immediate discontinuation of promethazine, antipsychotic drugs, if any, and other drugs not essential to concurrent therapy, 2) intensive symptomatic treatment and medical monitoring, and 3) treatment of any concomitant serious medical problems for which specific treatments are available. There is no general agreement about specific pharmacological treatment regimens for uncomplicated NMS. Since recurrences of NMS have been reported with phenothiazines, the reintroduction of promethazine should be carefully considered.
Other side effects have included paradoxical reactions. Hyperexcitability and abnormal movements have been reported in patients following a single administration of promethazine. Consideration should be given to the discontinuation of promethazine and to the use of other drugs if these reactions occur. Respiratory depression, nightmares, delirium, and agitated behavior have also been reported in some of these patients.
Ocular side effects have included blurred vision and diplopia.
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