Our library of drug research abstracts drawn from the medical literature is updated on a regular schedule, and you can be assured that new flexeril research articles will be listed here shortly after becoming available to us.
Related Sponsors
Medical research on flexeril
Clin Drug Investig. 2008; 28(12): 793-801
Darwish M, Hellriegel ET, Xie F
BACKGROUND AND OBJECTIVE: Cyclobenzaprine immediate release (CIR) has shown efficacy in the treatment of muscle spasm associated with acute, painful musculoskeletal conditions. An extended-release formulation of cyclobenzaprine (CER) has been developed to provide effective muscle spasm relief with once-daily dosing. The objective of this study was to compare the pharmacokinetics of CER and CIR. METHODS: This was a single-centre study of 18 healthy young adults (aged 18-45 years). Healthy volunteers were assigned to receive either a single dose of CER 30 mg or three doses of CIR 10 mg on days 1 and 15 (separated by a 14-day washout) in an open-label, two-period crossover study. Pharmacokinetic parameters were monitored through 168 hours after the last dose in each dose period; adverse events (AEs) were monitored during the study through 3 weeks after the last dose of study drug. Cyclobenzaprine was administered as a single oral 30 mg dose of CER or three 10 mg oral doses of CIR given every 8 hours over 24 hours. Statistical tests were conducted against a two-sided alternative hypothesis at a 0.05 level of significance with equivalence limits of 80% and 125%. Measures included area under the plasma cyclobenzaprine concentration versus time curve (AUC) to 168 hours and infinity, maximum plasma cyclobenzaprine concentration (C(max)), and time to observed C(max) (t(max)). RESULTS: Eighteen subjects were randomized and 17 completed both periods of the study. CER exhibited a consistent concentration-time profile with a single peak, in contrast to the pharmacokinetic profile for CIR, which displayed multiple peaks and troughs over the 24-hour period. The pharmacokinetic profile of CER 30 mg was characterized by an absorption phase with a median t(max) of approximately 6 hours, compared with the initial peak of CIR (following the first dose) of about 4 hours. Mean plasma concentrations at 4 hours were comparable (12.1 ng/mL for CER; 12.4 ng/mL for CIR). Systemic cyclobenzaprine exposure (AUC and C(max)) was similar across both formulations. The C(max) for CER 30 mg was 19.2 ng/mL (median t(max) = 6 hours) and for CIR (following the third dose) was 18.1 ng/mL (median t(max) = 12 hours). All AEs were mild in intensity; the most common AE was somnolence. CONCLUSION: The pharmacokinetic profile of once-daily CER reflected the mode of administration, providing a controlled release of cyclobenzaprine with sustained plasma concentrations, in contrast to the fluctuating profile of CIR. CER 30 mg once daily and CIR 10 mg three times daily resulted in comparable systemic exposures.
Choosing a skeletal muscle relaxant.
Am Fam Physician. 2008 Aug 1; 78(3): 365-70
See S, Ginzburg R
Skeletal muscle relaxants are widely used in treating musculoskeletal conditions. However, evidence of their effectiveness consists mainly of studies with poor methodologic design. In addition, these drugs have not been proven to be superior to acetaminophen or nonsteroidal anti-inflammatory drugs for low back pain. Systematic reviews and meta-analyses support using skeletal muscle relaxants for short-term relief of acute low back pain when nonsteroidal anti-inflammatory drugs or acetaminophen are not effective or tolerated. Comparison studies have not shown one skeletal muscle relaxant to be superior to another. Cyclobenzaprine is the most heavily studied and has been shown to be effective for various musculoskeletal conditions. The sedative properties of tizanidine and cyclobenzaprine may benefit patients with insomnia caused by severe muscle spasms. Methocarbamol and metaxalone are less sedating, although effectiveness evidence is limited. Adverse effects, particularly dizziness and drowsiness, are consistently reported with all skeletal muscle relaxants. The potential adverse effects should be communicated clearly to the patient. Because of limited comparable effectiveness data, choice of agent should be based on side-effect profile, patient preference, abuse potential, and possible drug interactions.
Neuralgic amyotrophy associated with antibiotic therapy.
Ann Pharmacother. 2008 Sep; 42(9): 1344-7
Finstad K, Guajardo JR, Scoville C
OBJECTIVE: To report a case of neuralgic amyotrophy associated with antibiotic therapy. CASE SUMMARY: A 22-year-old male with cystic fibrosis had been nonadherent to treatment for 4 years; when he returned to the clinic with symptoms, his forced expiratory volume in 1 second dropped from 84% predicted to 43% predicted. He was admitted to the hospital for treatment after failing to improve on oral ciprofloxacin and inhaled tobramycin. Treatment was initiated with intravenous tobramycin 560 mg daily and piperacillin/tazobactam 4.5 g infused every 6 hours. He continued inhaled tobramycin 300 mg twice daily, his home doses of pancreatic replacement enzymes and vitamins, albuterol 2.5 mg by high flow nebulizer (HFN) 4 times daily, and dornase alpha 2.5 by HFN daily. Sputum cultures were positive for methicillin-resistant Staphylococcus aureus, and intravenous vancomycin 1 g every 8 hours was added to the treatment regimen on hospital day 7. The patient developed bilateral shoulder pain followed by decreased function of his upper extremities 2 days later. He was treated with oral ibuprofen 600 mg every 6 h and oral cyclobenzaprine 5 mg daily, which improved his pain, but the shoulder stiffness remained throughout his hospital stay and persisted for 2 months following discharge. These symptoms resolved but recurred rapidly (within 24 h) and were more debilitating following a second exposure to the same antibiotics at the same doses 8 months later when the patient was readmitted for treatment of another cystic fibrosis-related pulmonary exacerbation. DISCUSSION: To our knowledge, this is the first case report illustrating neuralgic amyotrophy triggered by exposure to the antibiotics vancomycin, tobramycin, and piperacillin/tazobactam. After analysis of the case, ruling out other possibilities and using the Naranjo probability scale, we found that there is a highly probable likelihood that the symptoms presented by our patient were secondary to his drug therapy. Neuralgic amyotrophy is a rare condition of unknown etiology that has never before been associated with administration of these antibiotics, individually or in combination. Because of the specifics of the clinical history, we were unable to ascertain whether this complication was due to a single antibiotic or to the combination. It is quite possible that vancomycin was the only culprit, but impossible to ensure with the available evidence. CONCLUSIONS: Clinicians should be aware of this adverse reaction when facing similar complex neurologic symptoms in patients who are receiving the antibiotic treatment described here, especially vancomycin.
Pharmacotherapy. 2008 Feb; 28(2): 207-13
See S, Ginzburg R
Health care providers prescribe skeletal muscle relaxants for a variety of indications. However, the comparative efficacy of these drugs is not well known. Skeletal muscle relaxants consist of both antispasticity and antispasmodic agents, a distinction prescribers often overlook. The antispasticity agents-baclofen, tizanidine, dantrolene, and diazepam-aid in improving muscle hypertonicity and involuntary jerks. Antispasmodic agents, such as cyclobenzaprine, are primarily used to treat musculoskeletal conditions. Much of the evidence from clinical trials regarding skeletal muscle relaxants is limited because of poor methodologic design, insensitive assessment methods, and small numbers of patients. Although trial results seem to support the use of these agents for their respective indications, efficacy data from comparator trials did not particularly favor one skeletal muscle relaxant over another. Therefore, the choice of a skeletal muscle relaxant should be based on its adverse-effect profile, tolerability, and cost.
Extended-release cyclobenzaprine (Amrix).
Med Lett Drugs Ther. 2007 Dec 17; 49(1276): 102-3
Inappropriate prescribing in an older ED population.
Am J Emerg Med. 2007 Sep; 25(7): 804-7
Hustey FM, Wallis N, Miller J
The objective of this study was to determine the prevalence of potentially inappropriate medication (PIMs) use in older emergency department (ED) patients based on the updated 2002 Beers criteria. This was a retrospective analysis of 352 consecutive ED visits by patients aged 65 years and older. The mean number of medications taken was 8.4 per patient. In the study population, 111 (32%; 95% confidence interval [CI], 27-36) of 352 patients were taking at least 1 PIM at ED presentation. Propoxyphene/acetaminophen (24/352, 7%; 95% CI, 4-10), muscle relaxants (14/352, 4%; 95% CI, 2-7), and antihistamines (12/352, 3%; 95% CI, 2-6) were the most common PIMs. Among 101 of 193 patients discharged home from the ED with a new prescription, 13 (13%; 95% CI, 6-19) were also given PIMs. The most common PIMs were propoxyphene/acetaminophen (3/101; 95% CI, 1-8), diazepam (3/101; 95% CI, 1-8), cyclobenzaprine (2/101, 2%; 95% CI, 0-7), and diphenhydramine (2/101, 2%; 95% CI, 0-7). Outpatient PIM use in older ED patients is highly prevalent. Further education is needed regarding prescribing practices in this population group.
Pharmeur Sci Notes. 2005 Aug; 2005(1): 15-20
Dixon SP, Lodi A, Miller JH, Skellern GG
An isocratic reversed-phase liquid chromatographic method is described using a hybrid column for the control of synthetic impurities potentially found in amitriptyline hydrochloride. The method has been validated and is capable of controlling impurities to 0.1 per cent.
J Anal Toxicol. 2007 Jun; 31(5): 270-5
Melanson SE, Lewandrowski EL, Griggs DA, Flood JG
Patients taking tricyclic antidepressants (TCA) can experience toxicity or severe side effects. As a rapid and less technically demanding alternative to quantitative serum analysis, most laboratories offer qualitative immunoassays to assist in the evaluation of a suspected TCA overdose. However, the relationship between quantitative serum and qualitative urine levels of TCA-related compounds and their metabolites has not been comprehensively studied. Serum high-performance liquid chromatography results were compared to the qualitative urine results using the Syva Rapid Test and the Biosite Triage. Serum concentrations of amitriptyline, desipramine, doxepin, imipramine, and nortriptyline ranging from subtherapeutic to toxic triggered a positive response on both urine immunoassay devices. On the other hand, neither immunoassay uniformly detected clomipramine, even at serum levels greater than the therapeutic range. False positives due to cyclobenzaprine were more common with the Biosite assay. For virtually all positive urine TCA findings, it was not possible to determine whether the positive results corresponded to subtherapeutic, therapeutic, supratherapeutic, or toxic serum concentrations. Because urine immunoassays are the only option for many laboratories analyzing specimens for TCAs (especially in an emergency setting), clinicians must understand the limitations and interpret results in conjunction with clinical findings and/or quantitation of serum levels.
An internet survey of 2,596 people with fibromyalgia.
BMC Musculoskelet Disord. 2007; 8: 27
Bennett RM, Jones J, Turk DC, Russell IJ, Matallana L
BACKGROUND: This study explored the feasibility of using an Internet survey of people with fibromyalgia (FM), with a view to providing information on demographics, sources of information, symptoms, functionality, perceived aggravating factors, perceived triggering events, health care utilization, management strategies, and medication use. METHODS: A survey questionnaire was developed by the National Fibromyalgia Association (NFA) in conjunction with a task force of "experts in the field". The questionnaire underwent several rounds of testing to improve its face validity, content validity, clarity and readability before it was mounted on the internet. The questionnaire consisted of 121 items and is available online at the website of the National Fibromyalgia Association. RESULTS: The questionnaire was completed by 2,569 people. Most were from the United States, with at least one respondent from each of the 50 states. Respondents were predominantly middle-aged Caucasian females, most of whom had FM symptoms for > or = 4 years. The most common problems were morning stiffness, fatigue, nonrestorative sleep, pain, concentration, and memory. Aggravating factors included: emotional distress, weather changes, insomnia, and strenuous activity. Respondents rated the most effective management modalities as rest, heat, pain medications, antidepressants, and hypnotics. The most commonly used medications were: acetaminophen, ibuprofen, naproxen, cyclobenzaprine, amitriptyline, and aspirin. The medications perceived to be the most effective were: hydrocodone preparations, aprazolam, oxycodone preparations, zolpidem, cyclobenzaprine, and clonazepam. CONCLUSION: This survey provides a snap-shot of FM at the end of 2005, as reported by a self-selected population of people. This descriptive data has a heuristic function, in that it identifies several issues for further research, such as the prescribing habits of FM health care providers, the role of emotional precipitants, the impact of obesity, the significance of low back pain and the nature of FM related stiffness.
Psychol Health Med. 2006 Nov; 11(4): 498-506
García J, Simón MA, Durán M, Canceller J, Aneiros FJ
Given that studies about the differential efficacy of existing treatments in fibromyalgia syndrome are scarce, the aim of this study was to compare the differential efficacy of a cognitive-behavioral and a pharmacological therapy on fibromyalgia. Using a randomized controlled clinical trial, 28 fibromyalgic patients were assigned to one of following experimental conditions: (a) pharmacological treatment (i.e., cyclobenzaprine), (b) cognitive-behavioral intervention (i.e., stress inoculation training), (c) combined pharmacological and cognitive-behavioral treatment and (d) no treatment. The results show the superiority of cognitive-behavioral intervention to reduce the severity of fibromyalgia both at the end of the treatment and at follow-up. We conclude that cognitive-behavioral interventions must be considered a primary treatment of fibromyalgia syndrome.