Bennett fracture  is a type of partial broken finger involving the base of the thumb, and extends into the carpometacarpal (CMC) joint.Treatment typically requires surgery.This intra-articular fracture is the most common type of fracture of the thumb, and is nearly always accompanied by some degree of subluxation or frank dislocation of the carpometacarpal joint. Symptoms and signs
Symptoms of Bennett fracture are instability of the CMC joint of the thumb, accompanied by pain and weakness of the pinch grasp. Characteristic signs include pain, swelling, and ecchymosis around the base of the thumb and thenar eminence, and especially over the CMC joint of the thumb. Physical examination demonstrates instability of the CMC joint of the thumb. The patient will often manifest a weakened ability to grasp objects or perform such tasks as tying shoes and tearing a piece of paper. Other complaints include intense pain experienced upon catching the thumb on an object, such as when reaching into a pants pocket. Complications
Many important activities of daily life are dependent on the ability to grasp, pinch, and oppose the thumb. In fact, thumb function constitutes about 50% of overall hand function. These abilities are in turn dependent on an intact and functional thumb CMC joint.
The drug has a bioavailability of 90%, and peak plasma concentrations are seen after 2–4 hours. The mean drug half-life is approximately 11 hours. Mexiletine is predominantly metabolised by the liver. The pharmacokinetics of mexiletine are preserved with even moderate to severe renal impairment, but dose adjustment may be required when creatinine clearance falls below 10 mL/minute. Synthesis
Society and culture
Mexiletine is available for human use in the US, and has been reintroduced in the UK as a licensed product, having previously only been available as a named patient import. The drug is sold under the trade name Mexitil for use in arrhythmias and NaMuscla for use in myotonia. Veterinary uses
Mexiletine is available to veterinarians in the US for the treatment of heart disease in dogs and cats. It is commonly used for the treatment of arrhythmogenic right ventricular cardiomyopathy (ARVC) in Boxer dogs in combination with sotalol. References
Further reading
Peck T, Hill S, Williams M, eds. (2004). Pharmacology for Anaesthesia and Intensive Care (2nd ed.). Cambridge University Press. ISBN 0-521-68794-2. External links
"Mexiletine". Drug Information Portal. U.S. National Library of Medicine.