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| __NOTOC__
| | #REDIRECT [[Mexiletine#Warnings]] |
| {{Mexiletine}}
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| {{CMG}}; {{AE}} {{SS}}
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| ==Warnings and Precautions==
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| |[[File:Mexiletine01.jpg|thumb|800px]]
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| ===PRECAUTIONS===
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| ====General====
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| If a ventricular pacemaker is operative, patients with second or third degree heart block may be treated with mexiletine hydrochloride if continuously monitored. A limited number of patients (45 of 475 in controlled clinical trials) with preexisting first degree AV block were treated with mexiletine; none of these patients developed second or third degree AV block. Caution should be exercised when it is used in such patients or in patients with preexisting sinus node dysfunction or intraventricular conduction abnormalities.
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| Like other antiarrhythmics mexiletine hydrochloride can cause worsening of [[arrhythmias]]. This has been uncommon in patients with less serious [[arrhythmias]] (frequent premature beats or nonsustained ventricular [[tachycardia]]: see ADVERSE REACTIONS), but is of greater concern in patients with life-threatening [[arrhythmias]] such as sustained ventricular [[tachycardia]]. In patients with such [[arrhythmias]] subjected to programmed electrical stimulation or to exercise provocation, 10 to 15% of patients had exacerbation of the arrhythmia, a rate not greater than that of other agents.
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| Mexiletine should be used with caution in patients with [[hypotension]] and severe congestive [[heart failure]] because of the potential for aggravating these conditions. | |
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| Since mexiletine is metabolized in the liver, and hepatic impairment has been reported to prolong the elimination half-life of mexiletine, patients with liver disease should be followed carefully while receiving mexiletine. The same caution should be observed in patients with hepatic dysfunction secondary to congestive [[heart failure]].
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| Concurrent drug therapy or dietary regimens which may markedly alter urinary pH should be avoided during mexiletine hydrochloride therapy. The minor fluctuations in urinary pH associated with normal diet do not affect the excretion of mexiletine.
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| ====SGOT Elevation and Liver Injury====
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| In three month controlled trials, elevations of SGOT greater than three times the upper limit of normal occurred in about 1% of both mexiletine-treated and control patients. Approximately 2% of patients in the mexiletine compassionate use program had elevations of SGOT greater than or equal to three times the upper limit of normal. These elevations frequently occurred in association with identifiable clinical events and therapeutic measures such as congestive heart failure, acute myocardial infarction, blood transfusions and other medications. These elevations were often asymptomatic and transient, usually not associated with elevated bilirubin levels and usually did not require discontinuation of therapy. Marked elevations of SGOT (> 1000 U/L) were seen before death in four patients with end-stage cardiac disease (severe congestive heart failure, cardiogenic shock).
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| Rare instances of severe liver injury, including hepatic necrosis, have been reported in association with mexiletine treatment. It is recommended that patients in whom an abnormal liver test has occurred, or who have signs of symptoms suggesting liver dysfunction, be carefully evaluated. If persistent or worsening elevation of hepatic enzymes is detected, consideration should be given to discontinuing therapy.
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| ====Blood Dyscrasias====
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| Among 10,867 patients treated with mexiletine in the compassionate use program, marked [[leukopenia]] (neutrophils less than 1000/mm3) or [[agranulocytosis]]were seen in 0.06% and milder depressions of leukocytes were seen in 0.08%, and [[thrombocytopenia]] was observed in 0.16%. Many of these patients were seriously ill and receiving concomitant medications with known hematologic adverse effects. Rechallenge with mexiletine in several cases was negative. Marked leukopenia or [[agranulocytosis]] did not occur in any patient receiving mexiletine alone; five of the six cases of [[agranulocytosis]] were associated with [[procainamide]] (sustained release preparations in four) and one with vinblastine. If significant hematologic changes are observed, the patient should be carefully evaluated, and, if warranted, mexiletine should be discontinued. Blood counts usually return to normal within a month of discontinuation (see ADVERSE REACTIONS).
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| Convulsions (seizures) did not occur in mexiletine controlled clinical trials. In the compassionate use program, convulsions were reported in about 2 of 1000 patients. Twenty-eight percent of these patients discontinued therapy. [[Convulsions]] were reported in patients with and without a prior history of [[seizures]]. Mexiletine should be used with caution in patients with known [[seizure]] disorder.<ref name="dailymed.nlm.nih.gov">{{Cite web | last = | first = | title = MEXILETINE HYDROCHLORIDE CAPSULE [TEVA PHARMACEUTICALS USA INC] | url = http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=693da40b-26d4-40d6-87d1-158e256f40ab | publisher = | date = | accessdate = 3 March 2014 }}</ref>
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| ==References==
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| {{Reflist}}
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| {{Antiarrhythmic agents}}
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| [[Category:Sodium channel blockers]]
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| [[Category:Phenol ethers]]
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| [[Category:Cardiovascular Drugs]]
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| [[Category:Drugs]]
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