"Nov. 2, 2012 -- Safety steps taken in the wake of the fungal meningitis outbreak have worsened drug shortages, raising questions about whether the U.S. must choose between the safety and the availability of crucial medicines.
The most common adverse reactions in the two 14-day clinical efficacy trials and in the 7-day repeat-dose pharmacokinetic study are presented in Tables 5 and 6, respectively.
Table 5: Incidence of the Most Common Adverse
Reactions Occurring in ≥ 3% of Subjects in Any Treatment Group in the Two
Phase 3, Double-Blind AMRIX Trials
|AMRIX 15 mg
|AMRIX 30 mg
Table 6: Incidence of the
Most Common Adverse Reactions Occurring in ≥ 3% of Subjects in Any
Treatment Group in the Seven-Day Pharmacokinetic Study of AMRIX
|AMRIX 30 mg
N = 36
|Disturbance in attention||6%|
In a postmarketing surveillance program (7607 patients treated with cyclobenzaprine 10 mg TID), the adverse reactions reported most frequently were drowsiness, dry mouth, and dizziness. The incidence of these common adverse reactions was lower in the surveillance program than in the controlled clinical studies:
Table 7: Most Common Adverse
Reactions from Postmarketing Surveillance Program
|Clinical Studies cyclobenzaprine 10 mg TID||Surveillance Program cyclobenzaprine 10 mg TID|
Among the less frequent adverse reactions, there was no appreciable difference in incidence in controlled clinical studies or in the surveillance program. Adverse reactions which were reported in 1% to 3% of the patients were: fatigue/tiredness, asthenia, nausea, constipation, dyspepsia, unpleasant taste, blurred vision, headache, nervousness, and confusion. The following adverse reactions have been reported in post-marketing experience or with an incidence of less than 1% of patients in clinical trials with the 10 mg TID tablet:
Musculoskeletal: Local weakness.
Nervous System and Psychiatric: Seizures, ataxia; vertigo; dysarthria; tremors; hypertonia; convulsions; muscle twitching; disorientation; insomnia; depressed mood; abnormal sensations; anxiety; agitation; psychosis, abnormal thinking and dreaming; hallucinations; excitement; paresthesia; diplopia; serotonin syndrome.
Urogenital: Urinary frequency and/or retention.
Causal Relationship Unknown
Other reactions, reported rarely for cyclobenzaprine under circumstances where a causal relationship could not be established or reported for other tricyclic drugs, are listed to serve as alerting information to physicians:
Body as a Whole: Chest pain; edema.
Digestive: Paralytic ileus, tongue discoloration; stomatitis; parotid swelling.
Endocrine: Inappropriate ADH syndrome.
Metabolic, Nutritional and Immune: Elevation and lowering of blood sugar levels; weight gain or loss.
Nervous System and Psychiatric: Decreased or increased libido; abnormal gait; delusions; aggressive behavior; paranoia; peripheral neuropathy; Bell's palsy; alteration in EEG patterns; extrapyramidal symptoms.
Skin: Photosensitization; alopecia.
Drug Abuse And Dependence
Pharmacologic similarities among the tricyclic drugs require that certain withdrawal symptoms be considered when AMRIX is administered, even though they have not been reported to occur with this drug. Abrupt cessation of treatment after prolonged administration rarely may produce nausea, headache, and malaise. These are not indicative of addiction.
Read the Amrix (cyclobenzaprine hcl extended-release capsules) Side Effects Center for a complete guide to possible side effects »
AMRIX may have life-threatening interactions with monoamine oxidase (MAO) inhibitors see CONTRAINDICATIONS). Postmarketing cases of serotonin syndrome have been reported during combined use of cyclobenzaprine and other drugs such as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), tramadol, bupropion, meperidine, verapamil, or MAO inhibitors. If concomitant treatment with AMRIX and other serotonergic drugs is clinically warranted, careful observation is advised, particularly during treatment initiation or dose increases (see WARNINGS).
AMRIX may enhance the effects of alcohol, barbiturates, and other CNS depressants. Tricyclic antidepressants may block the antihypertensive action of guanethidine and similarly acting compounds. Tricyclic antidepressants may enhance the seizure risk in patients taking tramadol .
Last reviewed on RxList: 4/26/2013
This monograph has been modified to include the generic and brand name in many instances.
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