CYCLOBENZAPRINE HYDROCHLORIDE

Cyclobenzaprine hydrochloride, USP is a white to off-white crystalline powder with the molecular formula C 20 H 21 N•HCl and a molecular weight of 311.9. It has a melting point of 217° C, and a pK a of 8.47 at 25° C. It is freely soluble in water, in alcohol and in methanol, sparingly soluble in isopropanol, slightly soluble in chloroform and in methylene chloride and insoluble in hydrocarbons. If aqueous solutions are made alkaline, the free base separates. Cyclobenzaprine HCl is designated chemically as 3-( 5H -dibenzo[ a,d ] cyclohepten-5-ylidene)- N, N -dimethyl-1-propanamine hydrochloride, and has the following structural formula: Cyclobenzaprine hydrochloride tablets, USP are supplied as a 7.5 mg tablets for oral administration. Cyclobenzaprine hydrochloride 7.5 mg tablets contain the following inactive ingredients: corn starch, hydroxypropyl cellulose, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, pregelatinized starch, talc and titanium dioxide. structure

Cyclobenzaprine hydrochloride tablets, USP are indicated as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions. Improvement is manifested by relief of muscle spasm and its associated signs and symptoms, namely, pain, tenderness, limitation of motion, and restriction in activities of daily living. Cyclobenzaprine hydrochloride tablets, USP should be used only for short periods (up to two or three weeks) because adequate evidence of effectiveness for more prolonged use is not available and because muscle spasm associated with acute, painful musculoskeletal conditions is generally of short duration and specific therapy for longer periods is seldom warranted. Cyclobenzaprine hydrochloride tablets, USP has not been found effective in the treatment of spasticity associated with cerebral or spinal cord disease, or in children with cerebral palsy.

For most patients, the recommended dose of cyclobenzaprine hydrochloride tablets is 5 mg three times a day. Based on individual patient response, the dose may be increased to either 7.5 or 10 mg three times a day. Use of cyclobenzaprine hydrochloride tablets for periods longer than two or three weeks is not recommended. (see INDICATIONS AND USAGE ). Less frequent dosing should be considered for hepatically impaired or elderly patients (see PRECAUTIONS, Impaired Hepatic Function , and Use in the Elderly ).

Hypersensitivity to any component of this product. Concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation. Hyperpyretic crisis seizures, and deaths have occurred in patients receiving cyclobenzaprine (or structurally similar tricyclic antidepressants) concomitantly with MAO inhibitor drugs. Acute recovery phase of myocardial infarction, and patients with arrhythmias, heart block or conduction disturbances, or congestive heart failure. Hyperthyroidism.

Incidence of most common adverse reactions in the 2 double-blind ‡ , placebo-controlled 5 mg studies (incidence of > 3% on cyclobenzaprine hydrochloride tablets 5 mg): Cyclobenzaprine Hydrochloride Tablets 5 mg Cyclobenzaprine Hydrochloride Tablets 10 mg Placebo N = 464 N = 249 N = 469 Drowsiness 29% 38% 10% Dry Mouth 21% 32% 7% Fatigue 6% 6% 3% Headache 5% 5% 8% Adverse reactions which were reported in 1% to 3% of the patients were: abdominal pain, acid regurgitation, constipation, diarrhea, dizziness, nausea, irritability, mental acuity decreased, nervousness, upper respiratory infection, and pharyngitis. The following list of adverse reactions is based on the experience in 473 patients treated with cyclobenzaprine hydrochloride tablets 10 mg in additional controlled clinical studies, 7607 patients in the postmarketing surveillance program, and reports received since the drug was marketed. The overall incidence of adverse reactions among patients in the surveillance program was less than the incidence in the controlled clinical studies. The adverse reactions reported most frequently with cyclobenzaprine hydrochloride 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: ‡ Note: Cyclobenzaprine hydrochloride tablets 10 mg data are from one clinical trial. Cyclobenzaprine hydrochloride tablets 5 mg and placebo data are from two studies. Clinical Studies With Cyclobenzaprine Hydrochloride Tablets 10 mg Surveillance Program With Cyclobenzaprine Hydrochloride Tablets 10 mg Drowsiness 39% 16% Dry Mouth 27% 7% Dizziness 11% 3% 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 postmarketing experience or with an incidence of less than 1% of patients in clinical trials with the 10 mg tablet: Body as a Whole: Syncope; malaise. Cardiovascular: Tachycardia; arrhythmia; vasodilatation; palpitation; hypotension. Digestive: Vomiting; anorexia; diarrhea; gastrointestinal pain; gastritis; thirst; flatulence; edema of the tongue; abnormal liver function and rare reports of hepatitis, jaundice and cholestasis. Hypersensitivity: Anaphylaxis; angioedema; pruritus; facial edema; urticaria; rash. 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. Skin: Sweating. Special Senses: Ageusia; tinnitus. Urogenital: Urinary frequency and/or retention. Causal Relationship Unknown Other reactions, reported rarely for cyclobenzaprine hydrochloride 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. Cardiovascular: Hypertension; myocardial infarction; heart block; stroke. Digestive: Paralytic ileus, tongue discoloration; stomatitis; parotid swelling. Endocrine: Inappropriate ADH syndrome. Hematic and Lymphatic: Purpura; bone marrow depression; leukopenia; eosinophilia; thrombocytopenia. Metabolic, Nutritional and Immune: Elevation and lowering of blood sugar levels; weight gain or loss. Musculoskeletal: Myalgia. 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. Respiratory: Dyspnea. Skin: Photosensitization; alopecia. Urogenital: Impaired urination; dilatation of urinary tract; impotence; testicular swelling; gynecomastia; breast enlargement; galactorrhea.

Cyclobenzaprine may have life-threatening interactions with MAO inhibitors (see CONTRAINDICATIONS ). Postmarketing cases of serotonin syndrome have been reported during combined use of cyclobenzaprine hydrochloride and other drugs, such as selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), tramadol, bupropion, meperidine, verapamil, or monoamine oxidase (MAO) inhibitors. If concomitant treatment with cyclobenzaprine hydrochloride and other serotonergic drugs is clinically warranted, careful observation is advised, particularly during treatment initiation or dose increases (see WARNINGS ). Cyclobenzaprine hydrochloride 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. † † ULTRAM ® (tramadol HCl tablets, Ortho-McNeil Pharmaceutical) † ULTRACET ® (tramadol HCl and acetaminophen tablets, Ortho-McNeil Pharmaceutical)