Drug Interaction Report

Using dextromethorphan together with pheniramine may increase side effects such as dizziness, drowsiness, confusion, and difficulty concentrating. Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

MONITOR: Coadministration of quetiapine with drugs that possess serotonergic activity (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), etc.) may increase the risk of serotonin syndrome, a rare but serious and potentially fatal condition. Combining quetiapine with other serotonergic drugs may increase the risk of serotonin syndrome by relatively enhancing 5-HT1A receptor activity. However, data are currently limited to case reports. In one case report, an 85-year-old woman developed serotonin syndrome within hours of increasing quetiapine from 12.5 mg to 25 mg/day while also taking escitalopram, mirtazapine, sulpiride, and olanzapine; symptoms resolved within 48 hours after the discontinuation of all serotonergic medications. Symptoms of serotonin syndrome may include mental status changes such as irritability, altered consciousness, confusion, hallucination, and coma; autonomic dysfunction such as tachycardia, hyperthermia, diaphoresis, shivering, blood pressure lability, and mydriasis; neuromuscular abnormalities such as hyperreflexia, myoclonus, tremor, rigidity, and ataxia; and gastrointestinal symptoms such as abdominal cramping, nausea, vomiting, and diarrhea. In addition, central nervous system- and/or respiratory-depressant effects may be additively or synergistically increased in patients taking multiple drugs that also cause these effects (e.g., buspirone, desvenlafaxine, dextromethorphan, mianserin, reboxetine).

MANAGEMENT: Some authorities advise caution and closer monitoring for serotonin syndrome when quetiapine is coadministered with other serotonergic agents, especially during initiation and dose escalations. Patients should be instructed to promptly notify their healthcare provider if they experience symptoms of serotonin syndrome. If serotonin syndrome is suspected, a dose reduction or discontinuation of therapy should be considered depending on the severity of the symptoms. If serotonin syndrome develops during therapy, all serotonergic agents should be discontinued immediately, and supportive care rendered as necessary. Due to variability and occasionally prolonged half-lives of these coadministered agents, consulting individual product labeling for specific guidance is advised.

Using pheniramine together with QUEtiapine may increase side effects such as drowsiness, blurred vision, dry mouth, heat intolerance, flushing, decreased sweating, difficulty urinating, abdominal cramping, constipation, irregular heartbeat, confusion, and memory problems. Side effects may be more likely to occur in the elderly or those with a debilitating condition. You should avoid or limit the use of alcohol while being treated with these medications. Also avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medications affect you. Talk to your doctor if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Alcohol can increase the nervous system side effects of dextromethorphan such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with dextromethorphan. Do not use more than the recommended dose of dextromethorphan, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

Alcohol can increase the nervous system side effects of pheniramine such as dizziness, drowsiness, and difficulty concentrating. Some people may also experience impairment in thinking and judgment. You should avoid or limit the use of alcohol while being treated with pheniramine. Do not use more than the recommended dose of pheniramine, and avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how the medication affects you. Talk to your doctor or pharmacist if you have any questions or concerns.

Both phenylephrine and caffeine can increase blood pressure and heart rate, and combining them may enhance these effects. Talk to your doctor before using these medications, especially if you have a history of high blood pressure or heart disease. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.