Primary coronary artery dissection possibly related to drug hypersensitivity in a male

Primary coronary artery dissection is rare, usually affects females (greater than 85%), and has most often affected the left anterior descending coronary artery. The authors report a case that is unusual in four respects: the patient was male, the involved artery was a marginal branch of the circumflex, the resulting small infarct ruptured, and most importantly, the patient had recently experienced a drug hypersensitivity reaction. The microscopic finding of a heavy eosinophil and mast cell infiltrate around the dissected artery may indicate that dissection occurred as a result of hypersensitivity angiitis of the vasa vasorum, as has previously been suggested in the literature.

Influence of mexiletine on the pharmacokinetics of theophylline in healthy volunteers

Preliminary reports suggest an interaction exists between theophylline and mexiletine. We conducted a two-way crossover study in 15 healthy male subjects to assess the magnitude of the pharmacokinetic interaction between mexiletine and theophylline. Twelve subjects completed 5 days of therapy on sustained-release theophylline 200 mg every 12 hours alone and 5 days of therapy with theophylline and mexiletine 150 mg every 8 hours. The two treatment periods were separated by a minimum of 7 days. On the morning of day 5 of each treatment period, blood samples for theophylline to be assayed by fluorescence immunoassay were collected over 24 hours. Mexiletine significantly increased the mean AUC, Cmax, t1/2 beta, and Cl of theophylline. Mexiletine did not affect tmax or Vd. Side effects occurred in 4 subjects during treatment with theophylline alone all of which were judged to be mild in intensity. During concomitant theophylline-mexiletine therapy, 10 subjects reported side effects of which 4 were judged to be severe, 1 moderate, and 5 mild. The magnitude of the increase in theophylline plasma concentrations induced by mexiletine as measured by AUC (0-24) was 58%, which is similar to other preliminary reports of this interaction. The authors conclude that the magnitude of the pharmacokinetic interaction between theophylline and mexiletine may be clinically significant in patients in light of the increased incidence of side effects in our healthy subjects. Theophylline dosage adjustments will be required in patients who receive concomitant mexiletine therapy.

Mexiletine versus quinidine as first-line antiarrhythmia therapy: results from consecutive trials

The efficacy of mexiletine and quinidine in controlling ventricular couplets (VC) and ventricular tachycardia (VT) was compared in 156 trials (78 for each drug) in 114 consecutive patients. Forty-two patients received both drugs, whereas 36 patients were given mexiletine, and 36 patients received quinidine only. During acute drug testing, mexiletine was more effective than quinidine in controlling VC and VT (54 vs. 32 patients, respectively, P less than .001) and resulted in fewer proarrhythmic events (4 vs. 13, respectively, P less than .05). Mean duration of follow-up for mexiletine (27 +/- 14 mo) and quinidine (21 +/- 14 mo) did not differ. Long-term success was more frequent with mexiletine administration than quinidine administration (33/47 vs. 10/30 patients, respectively, P less than .01). The incidence of sudden death during follow-up with the two drugs did not differ overall, but more patients with ejection fraction greater than or equal to 40% died suddenly while taking quinidine than while receiving mexiletine (4/17 vs. 0/24, P less than .02). Mexiletine is as effective as quinidine for treating VC and VT and appears to be less proarrhythmic. It should be considered as an initial choice in the management of VC and VT.

Efficacy of combination therapy with mexiletine and a low dose of propranolol for premature ventricular arrhythmias

The clinical efficacy of combination therapy with mexiletine and propranolol was investigated in several centres. Twenty-four-hour Holter electrocardiograms were recorded and the severity of ventricular premature beats (VPBs) was assessed on the basis of the frequency of VPBs and according to the criteria of Lown. Forty-eight cases with VPBs received single treatment with mexiletine (300 mg/day). Single treatment with mexiletine was effective in 26 out of 48 cases (54%). Nineteen cases in which the single treatment with mexiletine was not sufficiently effective received combination therapy with mexiletine (300 mg/day) and a low dose of propranolol (30 mg/day). After the combination therapy, significant decreases in the frequency of VPBs were found in 11 out of 19 cases (58%), and lowering of the severity of the grade was found in 4 cases (30.8%). Thirteen out of 19 cases given combination therapy changed to single treatment with propranolol. A change in treatment from combination therapy to single treatment with propranolol was assessed as "undesirable" in 8 out of 13 cases (61.5%). During single treatment with mexiletine, side effects were found in 1 out of 48 cases (2.1%), and during the combination therapy in 1 out of 19 cases (5.2%). Thus, combination therapy with mexiletine and a low dose of propranolol was shown to be useful for patients with VPBs.

Long-term effect of mexiletine on left ventricular function and relation to suppression of ventricular arrhythmia

The effects of oral mexiletine on left ventricular (LV) ejection fraction (EF) and ventricular arrhythmias--and a possible relation between these effects--were evaluated during 3 months of therapy in 29 patients with chronic ventricular premature complexes (VPCs) and a moderately reduced to normal LVEF by 24-hour Holter monitoring and by radionuclide ventriculography at rest and during maximum tolerable exercise testing. After an average titration period of 13 days, a mean daily mexiletine dose of 739 mg was maintained throughout the treatment. At the end of titration and after 3 months of treatment, patients with a baseline LVEF less than or equal to 40% (group 2) responded with a median reduction of the hourly VPC rate by 90 and 81%, respectively, compared with 79 and 72% in those with a baseline LVEF greater than 40% (group 1). Couplets and runs of ventricular tachycardia were almost completely suppressed in nearly all patients. A single patient had a proarrhythmic increase in VPCs during treatment. Compared with baseline, there were no significant changes in resting or exercise LVEF after 1 or 3 months of treatment in either of the 2 groups of patients. No correlation was found between treatment-induced changes in arrhythmia frequency and in resting EF. No symptoms of congestive heart failure developed. The study confirms that long-term use of mexiletine is efficacious and relatively free of cardiac depressant effects even in patients with diminished LV function.

Interaction between theophylline and mexiletine

Drugs influencing hepatic microsomal enzyme systems, such as mexiletine, may affect the elimination pattern of theophylline. The three patients reported here had a history of asthma and premature ventricular contractions, and were receiving theophylline therapy. A few days after starting the coadministration of mexiletine and theophylline, theophylline serum concentrations increased about twofold over concentrations during theophylline therapy. In one case, theophylline serum concentrations increased by 2.6 fold, and the patient developed nausea and anorexia. Mexiletine serum concentrations did not change. It seems that with mexiletine therapy, lower doses of theophylline may be required and careful monitoring of serum concentrations is necessary.

Low dose quinidine-mexiletine combination therapy versus quinidine monotherapy for treatment of ventricular arrhythmias

Low dose quinidine-mexiletine combination therapy was compared with quinidine monotherapy in 15 patients with frequent ventricular premature complexes and nonsustained ventricular tachycardia in a dose escalation cross-over study. Oral combination therapy was initiated with quinidine gluconate (165 mg) plus mexiletine (150 mg) every 8 h. If ventricular premature complexes were not suppressed greater than or equal to 80% and nonsustained ventricular tachycardia greater than or equal to 90%, the dose was increased to a maximum of 330 mg of quinidine plus 200 mg of mexiletine. Quinidine monotherapy was initiated with 330 mg and escalated to a maximum of 660 mg every 8 h if criteria for effectiveness were not met. Combination quinidine-mexiletine therapy suppressed 80% of ventricular premature complexes in 13 of 14 patients and suppressed 100% of episodes of ventricular tachycardia in 6 of 8 patients (mean quinidine dose 200 +/- 70 mg; mean mexiletine dose 146 +/- 24 mg every 8 h). The mean effective trough quinidine and mexiletine concentration was 1.0 +/- 0.7 and 0.9 +/- 0.4 microgram/ml, respectively. Monotherapy was less effective; that is, greater than or equal to 80% suppression of ventricular premature complexes was observed in 5 of 15 patients and 100% suppression of ventricular tachycardia in 2 of 9 patients. The mean quinidine monotherapy dose was 462 +/- 155 mg every 8 h; the mean quinidine concentration was 1.8 +/- 0.8 microgram/ml. Adverse systemic effects occurred in 3 patients on quinidine-mexiletine therapy and in 11 on quinidine monotherapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Mexiletine. Long-term efficacy and side effects in patients with chronic drug-resistant potentially lethal ventricular arrhythmias

The antiarrhythmic efficacy of mexiletine hydrochloride (Mexitil) was evaluated in 100 patients with potentially lethal and drug-resistant ventricular arrhythmia. The efficacy of arrhythmia suppression was assessed by Holter monitoring. The overall arrhythmia suppression of ventricular premature contractions of 70% and greater was low and seen in only 22% of patients, with an additional 16% responding to a combination of mexiletine and an additional antiarrhythmic drug. The suppression of high-grade forms, couplets of 90% and greater, and complete abolition of nonsustained runs of ventricular tachycardia was achieved in 22% of patients, with 9% responding to the addition of another antiarrhythmic agent. Ventricular premature contractions, couplets, and nonsustained ventricular tachycardia were suppressed in only 16% of the cohort. The drug was poorly tolerated, with intolerable side effects developing in 49% of patients receiving mexiletine alone and in 57% of patients receiving a combination of antiarrhythmic agents. Tolerable adverse effects were relatively common but transient and dose related.

Prophylactic use of mexiletine in the elderly with acute myocardial infarction

A double blind randomised study comparing the effects of oral mexiletine and placebo given to elderly patients (65 years and older) immediately following hospital admission with suspected myocardial infarction (MI) is described. The study comprised one hundred and fifty-four patients of which 74 had confirmed myocardial infarction according to the diagnostic criteria of the study. Eighty patients without definite evidence of myocardial infarction were subsequently excluded from the study. Thirty-three patients (44.5%) with confirmed MI treated with mexiletine, compared with 41 (51%) in the placebo group showed no significant difference in mortality at 48 hours and 14 days. The mexiletine treated group showed a significant reduction (p less than 0.05) in certain forms of ventricular dysrhythmias. Six of these patients (18%) taking mexiletine had the drug withdrawn because of possible adverse drug reactions compared with two (4.8%) of the placebo group. None of the patients withdrawn because of possible adverse drug reactions had any long term side effect. Mild confusion observed in one patient was reversed after withdrawal of therapy. Results of this study indicate the safety of mexiletine as an anti-arrhythmic drug and its efficacy in suppression of certain ventricular dysrhythmias in the elderly with acute myocardial infarction. The overall mortality rate in both groups (mexiletine and placebo) remained unchanged.

Congestive heart failure induced by six of the newer antiarrhythmic drugs

The incidence of drug-induced congestive heart failure with several newer antiarrhythmic agents including encainide, ethmozine, lorcainide, mexiletine, propafenone and tocainide was determined in a group of 407 patients who underwent 1,133 drug tests. The incidence rate ranged from 0.7% with lorcainide to 4.7% with propafenone. Congestive heart failure was present in 167 patients (41%) who underwent 491 drug trials. Congestive failure was induced in 15 (9%) of these 167 patients and involved 19 (3.9%) of the 491 tests. Left ventricular ejection fraction was 20 +/- 8% in patients who developed congestive failure, in contrast to 39 +/- 19% in those who did not (p less than 0.001). It is concluded that each of the six antiarrhythmic drugs examined has the potential to aggravate congestive heart failure in patients with reduced left ventricular ejection fraction or a history of congestive heart failure, but the incidence rate is low and its occurrence unpredictable.

Efficacy of mexiletine in ventricular arrhythmias among patients in Taiwan: assessment by 24-hour Holter electrocardiography

The effects of mexiletine in 30 patients with symptomatic recurrent ventricular arrhythmias were assessed by 24-hour Holter electrocardiography and M-mode echocardiography. The mean daily dose of mexiletine was 534 mg (range, 300 to 900 mg) and the interval of Holter follow-up was 16.9 days (range, 10 to 25 days). Total ventricular premature beats were reduced by 85% or more in 21 patients; in 19 of these patients there was a reduction of one or more modified Lown grades of ventricular arrhythmias. The overall reduction in Lown grades in the 30 patients was from 3.3 +/- 0.8 to 1.5 +/- 1.4 (P less than 0.0001). No significant changes in heart rate before or after mexiletine therapy were noted. Left ventricular echocardiography showed no significant changes in percentage fractional shortening after treatment. Adverse effects included gastrointestinal intolerance in seven patients and neurogenic symptoms in three. During the follow-up period of 1 to 11 (mean, 3.2) months, ventricular arrhythmias recurred in three patients. It is concluded that oral mexiletine is moderately effective and safe in controlling symptomatic recurrent ventricular arrhythmias.

Mexiletine and tocainide: a comparison of antiarrhythmic efficacy, adverse effects, and predictive value of lidocaine testing

Thirty patients received one of the lidocaine analogues--mexiletine or tocainide--orally for treatment of symptomatic ventricular arrhythmias. Crossover to the other analogue was allowed if initial drug treatment was unsuccessful, and the controlled use of other marketed oral antiarrhythmic agents was permitted. After follow-up of 7 +/- 3 months (SD), mexiletine was successful in 5 of 13 patients initially and in 5 of 14 patients who failed to respond to tocainide. Tocainide was successful in 1 of 17 patients initially and in 2 of 7 who did not respond to mexiletine. Combination therapy was used in nearly half of all ultimately successful drug trials. A common cause of drug trial failure for both drugs was the occurrence of adverse effects that frequently appeared well after hospital discharge. Response to lidocaine was a sensitive but nonspecific predictor of clinical outcome with mexiletine or tocainide that helped to identify drug-resistant patients. Finally, although mexiletine provided effective antiarrhythmic therapy more often than tocainide, response to one lidocaine analogue did not predict response to the other.

Prolongation of ventricular depolarization. ECG manifestation of mexiletine toxicity

Mexiletine is a type 1B antiarrhythmic drug similar to lidocaine. Prolongation of ventricular depolarization has not been previously reported with the usual oral dosage of mexiletine. We describe a patient with renal failure and heart failure on low-dose oral therapy who developed mexiletine toxicity, which was manifested by ECG prolongation of ventricular depolarization. This was confirmed by elevated plasma concentration of mexiletine. This case illustrates that contrary to the usual belief, mexiletine pharmacokinetics are altered by renal failure. It is important to monitor mexiletine therapy by plasma levels in patients with impaired renal function to avoid mexiletine toxicity.

Prediction of efficacy and tolerance of oral mexiletine by intravenous lidocaine application

In a controlled crossover trial, 15 patients with frequent ventricular arrhythmias were treated with lidocaine to predict efficacy and safety of oral mexiletine. After an initial control period, patients received intravenous lidocaine (bolus infusion of 200 mg/20 min followed by 3.6 gm/24 hr and for 7 days oral mexiletine (200 mg four times a day). Efficacy was controlled by 24-hour Holter monitoring (responders = suppression of single premature ventricular beats [PVB] greater than 84% and of complex PVB greater than 90%). After lidocaine, 10 of 15 patients (67%) were responders (mean PVB reduction: 97%). After mexiletine, five of 15 patients (33%) were responders (mean PVB reduction: 81%); efficacy was closely related to the plasma concentration. When efficacy of both agents was compared, lidocaine infusion had a positive predictive value of only 50%; however, the negative predictive value was 100%. Thus in nonresponders to lidocaine, mexiletine is very likely to fail in the suppression of ventricular ectopy.

Clinical predictors of arrhythmia worsening by antiarrhythmic drugs

Aggravation of ventricular arrhythmia is a serious, potentially lethal, side effect that can occur with all antiarrhythmic agents. The purpose of this retrospective case-controlled study was to identify clinically useful parameters that would predict aggravation of arrhythmia. Patients in whom arrhythmia worsened while taking either quinidine, mexiletine or encainide were selected and matched to 2 similar patients who never developed this drug complication with any antiarrhythmic tested. A number of hemodynamic, electrophysiologic and pharmacologic parameters were compared. Only the presenting arrhythmia and a left ventricular ejection fraction less than 35% identified patients at risk for drug-induced aggravation of arrhythmia. Patients who presented with either sustained ventricular tachycardia or ventricular fibrillation were 3.4 times more likely to have arrhythmia aggravation compared with patients presenting with nonsustained ventricular tachycardia or ventricular premature beats. Patients with a left ventricular ejection fraction less than 35% were 2.2 times more likely to develop this drug complication compared with patients with an ejection fraction greater than 35%. There was no association between other clinical parameters, electrocardiographic intervals, ventricular arrhythmia density, drug dose or drug levels and aggravation of arrhythmia. In addition, drug aggravation to 1 drug did not predict its occurrence with another drug of the same class. Patients with a history of a sustained ventricular arrhythmia, especially when left ventricular dysfunction is present, are at high risk for the development of aggravation of arrhythmia.

Mexilitene use in pregnancy

Mexilitene, a class 1b antiarrhythmic, was used throughout an entire pregnancy to treat symptomatic premature ventricular contractions in a patient with mitral valve prolapse. Cord blood and maternal serum mexilitene levels at the time of delivery are given. The following conclusions were reached. (1) Mexilitene may have a future in treating pregnant patients with arrhythmias unresponsive to currently approved antiarrhythmic drugs. (2) Evidence to date has shown no adverse affects in infants of mothers breast-feeding while taking mexilitene. (3) Dosages need to be monitored carefully during pregnancy and the postpartum period to ensure that therapeutic drug levels are maintained.