5/26/2023 0 Comments Dorixina relaxElderly male subjects had the highest observed mean increase, approximately 2.4 fold (198.3 ng.hr/mL, range 155.6 to 255.3 versus 83.2 ng.hr/mL, range 41.1 to 142.5 for younger males) while levels in elderly females were increased to a much lesser extent, approximately 1.2 fold (143.8 ng.hr/mL, range 96.1 to 196.3 versus 115.9 ng.hr/mL, range 36.1 to 182.9 for younger females). In a pharmacokinetic study in elderly individuals, mean (n=10) steady-state cyclobenzaprine AUC values were approximately 1.7 fold (171.0 ng.hr/mL, range 96.1 to 255.3) higher than those seen in a group of eighteen younger adults (101.4 ng.hr/mL, range 36.1 to 182.9) from another study. (See PRECAUTIONS, Use in the Elderly and PRECAUTIONS, Impaired Hepatic Function. The plasma concentration of cyclobenzaprine is generally higher in the elderly and in patients with hepatic impairment. Cyclobenzaprine is eliminated quite slowly, with an effective half-life of 18 hours (range 8-37 hours n=18) plasma clearance is 0.7 L/min. Cytochromes P-450 3A4, 1A2, and, to a lesser extent, 2D6, mediate N-demethylation, one of the oxidative pathways for cyclobenzaprine. (n=18), peak plasma concentration was 25.9 ng/mL (range, 12.8-46.1 ng/mL), and area under the concentration-time (AUC) curve over an 8-hour dosing interval was 177 ng.hr/mL (range, 80-319 ng.hr/mL).Ĭyclobenzaprine is extensively metabolized, and is excreted primarily as glucuronides via the kidney. At steady state in healthy subjects receiving 10 mg t.i.d. Drug accumulates when dosed three times a day, reaching steady-state within 3-4 days at plasma concentrations about four-fold higher than after a single dose. Cyclobenzaprine exhibits linear pharmacokinetics over the dose range 2.5 mg to 10 mg, and is subject to enterohepatic circulation. Cyclobenzaprine caused slight to moderate increase in heart rate in animals.Įstimates of mean oral bioavailability of cyclobenzaprine range from 33% to 55%. Pharmacological studies in animals showed a similarity between the effects of cyclobenzaprine and the structurally related tricyclic antidepressants, including reserpine antagonism, norepinephrine potentiation, potent peripheral and central anticholinergic effects, and sedation. Evidence suggests that the net effect of cyclobenzaprine is a reduction of tonic somatic motor activity, influencing both gamma (γ) and alpha (α) motor systems. Such studies show that cyclobenzaprine acts primarily within the central nervous system at brain stem as opposed to spinal cord levels, although its action on the latter may contribute to its overall skeletal muscle relaxant activity. ![]() Animal studies indicate that cyclobenzaprine does not act at the neuromuscular junction or directly on skeletal muscle. ![]() It is ineffective in muscle spasm due to central nervous system disease.Ĭyclobenzaprine reduced or abolished skeletal muscle hyperactivity in several animal models. Dorixina Relax (Cyclobenzaprine Hydrochloride) contains the following inactive ingredients: colloidal silicon dioxide, croscarmellose sodium, dibasic calcium phosphate, hydroxypropyl cellulose, hypromellose, polyethylene glycol, magnesium stearate, microcrystalline cellulose, and titanium dioxide.ĭorixina Relax relieves skeletal muscle spasm of local origin without interfering with muscle function. Cyclobenzaprine HCl is designated chemically as 3-(5 H-dibenzocyclohepten-5-ylidene)- N,N-dimethyl-1-propanamine hydrochloride, and has the following structural formula:ĭorixina Relax (Cyclobenzaprine Hydrochloride) is available for oral administration as 7.5 mg tablets. If aqueous solutions are made alkaline, the free base separates. It is freely soluble in water and alcohol, sparingly soluble in isopropanol, and insoluble in hydrocarbon solvents. It has a melting point of 217☌, and a pK a of 8.47 at 25☌. ![]() Dorixina Relax (Cyclobenzaprine Hydrochloride) ® (cyclobenzaprine hydrochloride) is a white, crystalline tricyclic amine salt.
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