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Comfort Pac with Cyclobenzaprine and Prozac Weekly

Determining the interaction of Comfort Pac with Cyclobenzaprine and Prozac Weekly and the possibility of their joint administration.

Check result:
Comfort Pac with Cyclobenzaprine <> Prozac Weekly
Relevance: 23.06.2022 Reviewer: Shkutko P.M., M.D., in

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Consumer:

Talk to your doctor before using FLUoxetine together with cyclobenzaprine. Combining these medications can increase the risk of a rare but serious condition called the serotonin syndrome, which may include symptoms such as confusion, hallucination, seizure, extreme changes in blood pressure, increased heart rate, fever, excessive sweating, shivering or shaking, blurred vision, muscle spasm or stiffness, tremor, incoordination, stomach cramp, nausea, vomiting, and diarrhea. You should contact your doctor immediately if you experience these symptoms while taking the medications. 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.

Professional:

MONITOR CLOSELY: Concomitant use of cyclobenzaprine with other agents that possess serotonergic activity such as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), and monoamine oxidase (MAO) inhibitors may potentiate the risk of serotonin syndrome, which is a rare but serious and potentially fatal condition thought to result from hyperstimulation of brainstem 5-HT1A and 2A receptors. Symptoms of the 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.

A case report suggests that coadministration of cyclobenzaprine and fluoxetine may prolong QT interval of the electrocardiogram. The authors theorize that fluoxetine may inhibit the CYP450 3A4 metabolism of cyclobenzaprine, resulting in increased plasma concentrations of cyclobenzaprine and its dose-related cardiac effects. In the report, a 59-year-old woman who had been receiving long-term fluoxetine (30 mg daily) and cyclobenzaprine (10 mg daily) therapy demonstrated a prolonged baseline QTc (i.e., QT interval corrected for heart rate) of 497 msec five days prior to admission for surgery. Her other medications included amlodipine, diclofenac, and triamterene/HCTZ. During surgery, the patient developed torsade de pointes and then ventricular fibrillation presumably induced by the preoperative administration of droperidol, a drug with well-known QT prolonging and proarrhythmic effects. The patient had no known history of cardiac problems except for hypertension, and other potential causes such as congenital long QT syndrome and electrolyte abnormalities were ruled out. She received defibrillation and cardiopulmonary resuscitation, and QT interval returned to normal after the discontinuation of cyclobenzaprine and droperidol.

MANAGEMENT: Caution is advised if cyclobenzaprine and fluoxetine are used concomitantly or sequentially. Patients should be closely monitored for symptoms of the serotonin syndrome during treatment. Particular caution is advised when increasing the dosages of these agents. If serotonin syndrome develops or is suspected during the course of therapy, all serotonergic agents should be discontinued immediately and supportive care rendered as necessary. Moderately ill patients may also benefit from the administration of a serotonin antagonist (e.g., cyproheptadine, chlorpromazine). Severe cases should be managed under consultation with a toxicologist and may require sedation, neuromuscular paralysis, intubation, and mechanical ventilation in addition to the other measures.

Although data are weak, it may be advisable to also monitor the patient for development ventricular arrhythmias during coadministration of cyclobenzaprine and fluoxetine. ECG should be considered in susceptible patients, including those with underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). Any drug that can prolong the QT interval should be avoided with this combination if possible. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.

References
  • Michalets EL, Smith LK, Van Tassel ED "Torsade de pointes resulting from the addition of droperidol to an existing cytochrome P450 drug interaction." Ann Pharmacother 32 (1998): 761-5
  • Boyer EW, Shannon M "The serotonin syndrome." N Engl J Med 352 (2005): 1112-20
  • "Product Information. Flexeril (cyclobenzaprine)." Merck & Co, Inc, West Point, PA.
  • Keegan MT, Brown DR, Rabinstein AA "Serotonin syndrome from the interaction of cyclobenzaprine with other serotoninergic drugs." Anesth Analg 103 (2006): 1466-8
Comfort Pac with Cyclobenzaprine

Generic Name: cyclobenzaprine

Brand name: Amrix, Comfort Pac with Cyclobenzaprine, Fexmid, Flexeril

Synonyms: n.a.

Prozac Weekly

Generic Name: fluoxetine

Brand name: Prozac, Prozac Weekly, Sarafem, PROzac Pulvules, Rapiflux, Selfemra

Synonyms: n.a.

In the course of checking the drug compatibility and interactions, data from the following reference sources was used: Drugs.com, Rxlist.com, Webmd.com, Medscape.com.

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