Sibutramine and Fentanyl Transdermal Patch: Interaction Details

a) A case report describes opioid associated serotonin syndrome in a 58-year-old man with a history of chronic back pain. The patient was stable while receiving treatment for pain and depression. His medication regimen included transdermal fentaNYL 75 mcg/hr patches, oxyCODONE 5 mg/acetaminophen 325 mg twice daily, celecoxib 200 mg twice daily, citalopram 40 mg once daily, and mirtazapine 50 mg at night. The patient was also receiving doxazosin 4 mg daily and zolpidem 12.5 mg as needed for insomnia. The patient reported inadequate pain control and treatment with fentaNYL was altered to replacing the patch every 2 days from every 3 days. Approximately 1 week after the fentaNYL dose increase, the patient reported anxiety, tremulousness, fever, and sweating. CloNIDine 0.2 mg every 4 hours was instituted without improvement in symptoms. The patient continued to have persistent symptoms and the following day was given haloperidol and LORazepam to treat anxiety and agitation. The patient discontinued his fentaNYL patch and presented to the emergency room with opiate withdrawal 2 days later. The patient was then diagnosed with serotonin syndrome despite discontinuing his fentaNYL patch for 30 hours. Treatment with haloperidol, fentaNYL, oxyCODONE/acetaminophen, citalopram, and mirtazapine were immediately discontinued with a complete resolution of symptoms by the following day. The patient was prescribed morphine sulfate to replace fentaNYL therapy, and was restarted on citalopram and mirtazapine with no recurrence of serotoninergic symptoms on follow-up ⁵.

b) Serotonin syndrome associated with fentaNYL use during an esophagogastroduodenoscopy was reported in a 39-year-old woman also taking sertraline 100 mg daily as an outpatient. The patient initially presented with hematemesis and a history of alcoholic cirrhosis. Prior to the esophagogastroduodenoscopy, an octreotide and pantoprazole drip was started, 2 doses of fentaNYL 50 micrograms, and 2 doses of midazolam 1 mg were administered. The patient became somnolent and extremely rigid in all four extremities following the procedure, and vecuronium and etomidate were given for immediate intubation. The rigidity progressed with diffuse diaphoresis, horizontal roving eye movements, and a fever of 105 degrees F. Due to the potential for seizure activity, LORazepam 2 mg IV was given with no improvement and a propofol drip was started for continued sedation during intubation. A CPK value of 2800 units/L and an ammonia level of 340 micromols/L indicated rhabdomyolysis. An acute intracranial process was ruled out on a CT scan of the brain and the neurology team made the diagnosis of serotonin syndrome secondary to an interaction between fentaNYL and sertraline. Propofol was continued for sedation and the patient received supportive treatment with a cooling blanket and cyproheptadine. After 3 days, the patient's temperature and CPK level normalized and she later extubated with no further complications ⁶.

c) Serotonin syndrome following the administration of IV fentaNYL during surgical procedures was reported in 2 patients also taking SSRIs (sertraline and escitalopram). The first patient received IV fentaNYL (50 mcg), midazolam (2 mg), and 2 doses propofol (60 mg and 40 mg) in an outpatient surgery center prior to a carpal tunnel release procedure. Postoperatively the patient began shivering and became increasingly agitated for which she was transferred to the emergency department. On presentation the patient was combative, diaphoretic, confused, was unable to follow commands, tachycardic, hypertensive, had hyperreflexia, and ankle clonus. Baseline creatinine kinase rose to 613 units/L on day 2 of hospitalization. The toxicology service treated her with escalating doses of benzodiazepines with no improvement. The patient was subsequently intubated and sedated with a continuous propofol infusion. After 2 days the patient was extubated and by day 3 all symptoms had resolved and the patient was discharged home. The second patient was a 59-year-old woman admitted for an omentectomy for which she received IV fentaNYL 250 micrograms, etomidate, vecuronium, morphine and cephazolin. Following extubation the patient became hypoxic and acidotic and was reintubated and transferred to the ICU. On postoperative day 1 she was extubated and later became tachycardic and was unable to follow commands. On examination the patient was agitated and diaphoretic, had patellar hyperreflexia and a bilateral 3 to 4 beat ankle clonus. Laboratory evaluation was remarkable for a peak creatine kinase of 1161 units/L on postoperative day 2. The patient was treated with LORazepam and cyproheptadine with resolution of symptoms after 3 days ⁷.

d) A case of postoperative serotonin syndrome following the administration of fentaNYL for general anesthesia and post operative analgesia was reported in a 60-year-old woman also receiving PARoxetine. Outpatient medications included only PARoxetine and thyroxine for a history of depression and hypothyroidism. The patient was admitted for an extensive resection of a recurrent left chest wall myxofibrosarcoma and given propofol and 200 mcg of fentaNYL for the induction of anesthesia. The patient also received an additional 800 mcg of fentaNYL (intermittent 50 mcg boluses) intraoperatively and a subsequent fentaNYL infusion (100 to 200 mcg/hr) for postoperative sedation and analgesia (2545 mcg of fentaNYL received over 36 hours). The fentaNYL infusion was continued 36 hours postoperatively, at which time intermittent agitation, bilateral hypertonia and hyperreflexia, and bilateral inducible ankle clonus were observed on neurological examination. Symptoms were more severe in the lower limbs and on the right side of the body. A CT scan of the brain was unremarkable and all other examination findings, including a thyroid function test, were within normal limits with the exception of elevated blood pressure (180/90 mmHg), which spontaneously resolved 24 hours after the procedure. fentaNYL was discontinued, and 24 hours later, there was marked improvement in neurological symptoms and complete recovery by postoperative day 4. The patient was ultimately discharged home with no further complications ⁸.

e) A 65-year-old woman treated with citalopram for depression experienced serotonin syndrome following initiation of fentaNYL patch. She was recently diagnosed with myelodysplastic/myeloproliferative disease and her regular medication regimen included RABEprazole, tolterodine, HYDROcodone, and over-the-counter NSAIDS. She was hospitalized upon presentation of abdominal pain and worsening back pain, and a spontaneous retroperitoneal hemorrhage was discovered. While hospitalized, her worsening back pain was treated with fentaNYL transdermal patch (25 mcg/hr). Within 24 hours of fentaNYL initiation, she progressively developed increasing confusion, agitation, combativeness, tremors in the upper extremities, myoclonic jerks, hyperreflexia, and unsteady gait; consistent with serotonin syndrome. Tachycardia was also observed (110 to 120 beats per minute). A CT scan and laboratory values did not reveal any abnormalities. fentaNYL was discontinued. and all of her symptoms resolved within 24 to 36 hours. Her symptoms did not recur with initiation of oxyCODONE for the treatment of the back pain. The association of this serotonin syndrome with the coadministration of fentaNYL and citalopram in this case was deemed probable based on the Naranjo adverse event probability scale ⁹.