Chlorzoxazone

Chlorzoxazone is a muscle-relaxing drug,and a probe for human liver cytochrome P-450IIE1.

Comparative study of different approaches for preparation of chlorzoxazone orodispersible tablets.[Pubmed:27534668]

Drug Dev Ind Pharm. 2017 May;43(5):742-750.

CONTEXT: Muscle spasm is a painful involuntary contraction of muscles, which causes involuntary movement and distortion. Chlorzoxazone is a centrally acting muscle-relaxant with sedative properties, but given orally, it is hepatically metabolized leading to decreased bioavailability. OBJECTIVE: Orodispersible tablets (ODTs) of Chlorzoxazone were formulated using two different approaches; by coprocessed excipients (CE) or by liquisolid (LS) technique. MATERIALS AND METHODS: Pharmaburst((R)) 500, Starlac((R)), Pearlitol flash((R)), Prosolv((R)) odt and F-melt((R)) were used as coprocessed superdisintegrants, whereas in LS, Avicel((R)) PH101, Microcelac((R)) 100 and Cellactose((R)) 80 were used as carriers, while Aerosil((R)) 200 was the coating material. ODTs were evaluated in terms of weight and thickness variations, drug content, hardness, friability, wetting time, dissolution, disintegration time (DT) and palatability. RESULTS: In vitro DT of CE-ODTs ranged from 26.43 +/- 1.693 s to >180 s, whereas it was between 25.42+/- 0.203 s to >180 s in LS-ODTs. Complete drug release within 15 min was attained by CE1 prepared with 92.5 mg Pharmaburst((R)) 500. In vivo DT of CE1 and LS3 were 19.779 +/- 0.810 and 18.105 +/- 0.423 s, respectively, using six volunteers. Volunteers found that CE1 had more acceptable taste and was more palatable than LS3. CONCLUSION: It was concluded that Chlorzoxazone ODTs could be successfully formulated using either CE or LS techniques and be used as novel dosage forms for pediatrics and geriatrics showing improved drug release. Moreover, CE technique was superior to LS technique in terms of palatability.

Effect of piperine on CYP2E1 enzyme activity of chlorzoxazone in healthy volunteers.[Pubmed:27670974]

Xenobiotica. 2017 Dec;47(12):1035-1041.

1. The purpose of the present study was to investigate the effect of piperine (PIP) on CYP2E1 enzyme activity and pharmacokinetics of Chlorzoxazone (CHZ) in healthy volunteers. 2. An open-label, two period, sequential study was conducted in 12 healthy volunteers. A single dose of PIP 20 mg was administered daily for 10 days during treatment phase. A single dose of CHZ 250 mg was administered during control and after treatment phases under fasting conditions. The blood samples were collected at predetermined time intervals after CHZ dosing and analyzed by HPLC. 3. Treatment with PIP significantly enhanced maximum plasma concentration (Cmax) (3.14-4.96 mug/mL), area under the curve (AUC) (10.46-17.78 mug h/mL), half life (T1/2) (1.26-1.82 h) and significantly decreased elimination rate constant (Kel) (0.57-0.41 h (-) (1)), apparent oral clearance (CL/F) (24.76-13.65 L/h) of CHZ when compared to control. In addition, treatment with PIP significantly decreased Cmax (0.22-0.15 mug/mL), AUC (0.94-0.68 mug h/mL), T1/2 (2.54-1.68 h) and significantly increased Kel (0.32-0.43 h (-) (1)) of 6-hydroxyChlorzoxazone (6-OHCHZ) as compared to control. Furthermore, treatment with PIP significantly decreased metabolite to parent (6-OHCHZ/CHZ) ratios of Cmax, AUC, T1/2 and significantly increased Kel ratio of 6-OHCHZ/CHZ, which indicate the decreased formation of CHZ to 6-OHCHZ. 4. The results suggest that altered pharmacokinetics of CHZ might be attributed to PIP mediated inhibition of CYP2E1 enzyme, which indicate significant pharmacokinetic interaction present between PIP and CHZ. The inhibition of CYP2E1 by PIP may represent a novel therapeutic benefit for minimizing ethanol induced CYP2E1 enzyme activity and results in reduced hepatotoxicity of ethanol.

Effect of Cholesterol on the Interaction of Cytochrome P450 Substrate Drug Chlorzoxazone with the Phosphatidylcholine Bilayer.[Pubmed:27347790]

Biochemistry. 2016 Jul 19;55(28):3888-98.

Many drugs are oxidized by membrane protein cytochrome P450 (CYP) enzymes during their metabolism process. CYPs are located mainly in endoplasmic reticulum (ER) membranes. Recent studies have suggested that CYP substrate drugs first bind the lipid bilayers of ER membranes and then the drugs reach the active site of CYP by way of an access channel. The entrance of the channel is located in the hydrophobic regions of the lipid bilayers. One of the features of the ER membrane is a cholesterol content that is lower than those of other biomembranes. In this study, the cholesterol concentration dependence of the interaction of a CYP substrate drug, Chlorzoxazone (CZX), with model membranes composed of phosphatidylcholine (PC) and cholesterol was examined via differential scanning calorimetry (DSC), UV-visible spectroscopy, and X-ray diffraction. Experimental results indicated that CZX can bind to pure PC bilayers in the absence of cholesterol and that, by contrast, a high cholesterol concentration (30-50 mol %) tends to prevent CZX from binding to PC bilayers. Interestingly, the effect of cholesterol on the binding and insertion of CZX was biphasic. In the case of palmitoyloleoylphosphatidylcholine (POPC) bilayers containing 5-10 mol % cholesterol, the CZX's binding and penetration into the bilayer were found to be greater than those with pure POPC bilayers. The concentration of 5-10 mol % nearly corresponds to the cholesterol concentration of ER membranes. The low cholesterol contents (12-20 mol %) of ER membranes might be the most suitable for the CYP drug metabolism process in ER membranes.

The effect of chlorzoxazone on acute pain after spine surgery. A randomized, blinded trial.[Pubmed:27306492]

Acta Anaesthesiol Scand. 2016 Sep;60(8):1152-60.

BACKGROUND: Chlorzoxazone is a muscle relaxant administered for musculoskeletal pain, and as an analgesic adjunct for post-operative pain. Chlorzoxazone for low back pain is currently not advised due to the lack of placebo-controlled trials. We explored the effect of Chlorzoxazone on acute pain after spine surgery. METHODS: One hundred and ten patients were randomly assigned to 500 mg oral Chlorzoxazone or placebo in this blinded study of patients having spine surgery under general anaesthesia. In the 4 h trial period analgesia consisted of IV patient-controlled analgesia (morphine bolus 2.5 mg). Primary outcome was pain during mobilization (visual analogue scale) 2 h after the intervention. Secondary outcomes were pain at rest, opioid consumption, nausea, vomiting, sedation and dizziness. RESULTS: For pain during mobilization 2 h after intervention, there was no significant difference between groups: 51 (21) vs. 54 (25) mm in the Chlorzoxazone and placebo groups, respectively, mean difference 3 mm (95% CI -8 to 10), P = 0.59. For pain during mobilization and at rest (wAUC 1-4 h), there were no significant differences between groups. There was no significant difference in total IV morphine use 0-4 h: median 10 (7-21) vs. 13 (5-19) mg in the Chlorzoxazone and placebo groups, respectively, P = 0.82. We found no significant difference in adverse effects. CONCLUSION: No analgesic effect of single-dose Chlorzoxazone was demonstrated in patients with acute pain after spine surgery. Based on these findings, Chlorzoxazone cannot be recommended for immediate treatment of acute pain after such procedures.