Empiric long-term amiodarone prophylaxis following myocardial infarction. A meta-analysis.

BACKGROUND: The prophylactic administration of amiodarone following acute myocardial infarction has been investigated in several small trials. This study combined the results of these small trials in a meta-analysis to determine the effects of prophylactic low-dose amiodarone on mortality following acute myocardial infarction. METHODS: Four prospective, randomized, placebo-controlled trials, which investigated the prophylactic administration of low-dose amiodarone (200 to 400 mg/d) to patients after acute myocardial infarction, were selected from the current literature according to strict inclusion criteria. A total of 1140 patients, 566 in the amiodarone-treated group and 574 in the placebo-treated group, were included in the analysis. Sudden cardiac death, cardiac mortality, and total mortality were the end points of interest. In addition, the effect of impaired left ventricular function (ejection fraction, < 45%) on total mortality was assessed. Data were aggregated by using the Mantel-Haenszel method to obtain final summary statistics for these end points. RESULTS: Patients treated with low-dose amiodarone exhibited a lower incidence of sudden cardia death (3.1%) and total mortality (6.1%) when compared with patients treated with placebo (6.9% and 11.2%, respectively; both P < .01; and 95% confidence interval [CI], 0.011 to 0.065 and 0.013 to 0.082, respectively). There was no significant difference between the amiodarone- and placebo-treated groups with respect to cardiac mortality (2.6% vs 3.7%, respectively; P = .26; and 95% CI, -0.012 to 0.032). For patients with a left ventricular ejection fraction of less than 45%, total mortality was 5.5% in the amiodarone-treated group and 9.4% in the placebo-treated group (P = .30; CI, -0.023 to 0.101). CONCLUSIONS: Although further data from ongoing large, randomized trials are needed, this meta-analysis suggests that the prophylactic administration of low-dose amiodarone to patients following acute myocardial infarction reduces the incidence of both sudden cardiac death and total mortality. The benefits of low-dose amiodarone may be limited to patients with preserved left ventricular function.

Treatment of resistant atrial fibrillation. A meta-analysis comparing amiodarone and flecainide.

BACKGROUND: Chronic atrial fibrillation (AF) is a common arrhythmia with significant morbidity and mortality. Maintenance of normal sinus rhythm (NSR) can be achieved with antiarrhythmic drug therapy. The antiarrhythmic effects of amiodarone hydrochloride and flecainide acetate in patients with resistant chronic AF have been investigated separately in several small studies. This investigation compared amiodarone to flecainide in maintaining NSR in patients with resistant chronic AF. METHODS: Studies using amiodarone or flecainide in the treatment of patients with chronic AF refractory to class I antiarrhythmic drugs or sotalol hydrochloride were identified. The results of six trials of amiodarone (200 to 400 mg/d, 315 patients) and two trials of flecainide (200 to 300 mg/d, 163 patients) were aggregated using meta-analytic techniques. The percentages of patients taking amiodarone or flecainide and remaining in NSR at 3 and 12 months were compared relative to results for quinidine, which were acquired from a meta-analysis of quinidine used as first-line therapy for AF. RESULTS: After 3 and 12 months of treatment with amiodarone, 217 (72.6%) of 299 patients and 64 (59.8%) of 107 patients, respectively, remained in NSR. These percentages were significantly greater (P < .0001) than those for quinidine (70% and 50%, respectively). For flecainide, the percentage of patients remaining in NSR was significantly lower (P < .0001) than for quinidine: 79 (48.5%) and 56 (34%) of 163 patients, respectively. The aggregated percentages of patients requiring withdrawal of amiodarone and flecainide were similar: 9.5% and 8.6%, respectively. Mortality and proarrhythmia could not be assessed. CONCLUSION: This analysis suggests that low-dose amiodarone is more efficacious and equally well tolerated when compared with flecainide in the management of chronic, drug-resistant AF.

Pharmacokinetic interaction between intravenous phenytoin and amiodarone in healthy volunteers.

To determine the mechanism of the amiodarone-phenytoin interaction, seven healthy male subjects were given intravenous phenytoin, 5 mg/kg, before (phase I) and after (phase II) 3 weeks of oral amiodarone, 200 mg/day. Serum AUC increased from 245 +/- 37.6 to 342 +/- 87.3 mg.hr/L (p = 0.007); area under the first moment curve increased from 5666 +/- 1003 to 11,632 +/- 4198 mg.hr2/L (p = 0.008); the time-averaged total body clearance decreased from 1.57 +/- 0.3 to 1.17 +/- 0.33 L/hr (p = 0.0004); and the apparent elimination half-life increased from 16.1 +/- 1.32 to 22.6 +/- 3.8 hours (p = 0.001) for phenytoin during phase II. The volume of distribution at steady state and the unbound fraction for phenytoin remained unchanged. However, the formation of p-hydroxyphenytoin as a function of serum phenytoin concentration decreased during phase II. These findings suggest that amiodarone inhibits phenytoin metabolism. These observations also suggest that phenytoin doses will need to be reduced when coadministered with amiodarone. The magnitude of this reduction is difficult to predict because of the saturable pharmacokinetics of phenytoin, and therapeutic monitoring is recommended if amiodarone is added to the phenytoin regimen.

Meta-analysis of the use of low-dose beta-adrenergic blocking therapy in idiopathic or ischemic dilated cardiomyopathy.

We concluded that low-dose beta-adrenergic blocking agents are beneficial in the treatment of patients with ischemic or idiopathic cardiomyopathy. Low-dose beta blockers appear to improve NYHA functional class and LVEF.

Steady-state interaction between amiodarone and phenytoin in normal subjects.

Amiodarone has been reported to increase phenytoin levels. This study was designed to evaluate the pharmacokinetic basis of this interaction at steady-state. Pharmacokinetic parameters for phenytoin were determined after 14 days of oral phenytoin, 2 to 4 mg/kg/day, before and after oral amiodarone, 200 mg daily for 6 weeks in 7 healthy male subjects. During amiodarone therapy, area under the serum concentration time curve for phenytoin was increased from 208 +/- 82.8 (mean +/- standard deviation) to 292 +/- 108 mg.hr/liter (p = 0.015). Both the maximum and 24-hour phenytoin concentrations were increased from 10.75 +/- 3.75 and 6.67 +/- 3.51 micrograms/ml to 14.26 +/- 3.97 (p = 0.016) and 10.27 +/- 4.67 micrograms/ml (p = 0.012), respectively, during concomitant amiodarone treatment. Amiodarone caused a decrease in the oral clearance of phenytoin from 1.29 +/- 0.30 to 0.93 +/- 0.25 liters/hr (p = 0.002). These results were due to a reduction in phenytoin metabolism by amiodarone as evidenced by a decrease in the urinary excretion of the principal metabolite of phenytoin, 5-(p-hydroxyphenyl)-5-phenylhydantoin, 149 +/- 39.7 to 99.3 +/- 40.0 mg (p = 0.041) and no change in the unbound fraction of the total phenytoin concentration expressed as a percentage, 10.3 +/- 2.7 versus 10.7 +/- 2.1% (p = 0.28) during coadministration of amiodarone. The alterations in phenytoin pharmacokinetics suggest that steady-state doses of phenytoin of 2 to 4 mg/kg/day should be reduced at least 25% when amiodarone is concurrently administered. All dosage reductions should be guided by clinical and therapeutic drug monitoring.

Effectiveness and costs of digoxin treatment for atrial fibrillation and flutter.

Clinical outcomes and costs associated with the use of digoxin in atrial fibrillation and flutter were evaluated in a prospective, observational study at 18 academic medical centers in the United States. Data were collected on 115 patients (aged > 18 years) with atrial fibrillation or flutter who were treated with digoxin for rapid ventricular rate (> or = 120 beats/min). The median time to ventricular rate control (i.e., resting ventricular rate < 100 beats/min, decrease in ventricular rate of > 20%, or sinus rhythm) was 11.6 hours from the first dose of digoxin for all evaluable patients (n = 105) and 9.5 hours for those only receiving digoxin (n = 64). Before ventricular rate control, the mean +/- SD dose of digoxin administered was 0.80 +/- 0.74 mg, and a mean of 1.4 +/- 1.8 serum digoxin concentrations were ordered per patient. Concomitant beta-blocker or calcium antagonist therapy was instituted in 47 patients (41%); in 19 of these, combination therapy was initiated within 2 hours. Adenosine was administered to 13 patients (11%). Patients spent a median of 4 days (range 1 to 25) in the hospital; 28% spent time in a coronary/intensive care unit and 79% in a telemetry bed. Loss of control (i.e., resting ventricular rate returned to > 120 beats/min) occurred at least once in 50% of patients and was associated with a longer hospital stay (p < 0.05). Based on 1991 data, the estimated mean hospital bed cost for patients with atrial fibrillation or flutter was $3,169 +/- $3,174.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclosporine interactions with miconazole and other azole-antimycotics: a case report and review of the literature.

Several antimicrobial drugs have been shown to pharmacokinetically interact with cyclosporine. On two separate occasions, we observed increases in cyclosporine plasma concentrations during concomitant miconazole therapy in a heart transplant patient with an infection secondary to Pseudallescheria boydii. To our knowledge, no interaction between cyclosporine and miconazole has previously been reported. In addition, drug interactions were observed between cyclosporine and ketoconazole and possibly between cyclosporine and SCH 39304, an investigational azole-antifungal agent. No interaction was noted between cyclosporine and fluconazole. In general, clinicians should anticipate drug interactions between cyclosporine and azole-antimycotic agents.

Prospective study of the safety and financial benefit of ketoconazole as adjunctive therapy to cyclosporine after heart transplantation.

In a prospective study of the relative safety and potential benefit of concomitant ketoconazole and cyclosporine after heart transplantation, 15 transplant recipients were followed up for up to 1 year (mean, 10.7 months) after ketoconazole was added to their immunosuppressive regimen of cyclosporine, prednisone, and azathioprine, and these patients were compared with a matched cohort over the same time. There was an 88% reduction in the mean (+/- SD) dose of cyclosporine, from 394 (115) mg/day to 47 (21) mg/day (p less than 0.0005) in the ketoconazole group, compared with an insignificant change in the control group. The projected annual cost of cyclosporine was reduced by 88%, with a 72% reduction in the projected cost of immunosuppressive drugs and prophylactic antifungal therapy, from a mean of $6800 to $1862 per year per transplant recipient in the ketoconazole-treated group. Other beneficial effects found over the study period included a significant reduction in the mean and diastolic systemic arterial pressure and a significant reduction in serum cholesterol. The mean total serum cholesterol fell from 265 (44) to 204 (38) mg/dl in the ketoconazole group but did not change significantly in the control group (p less than 0.005). Low-density lipoprotein cholesterol also fell from a mean of 167 (32) mg/dl to 112 (28) mg/dl (p less than 0.005). Renal function was not significantly affected by ketoconazole when compared with the control group. Ketoconazole and other drugs of potential use in organ transplant recipients should be evaluated for financial as well as for other potential clinical benefits in the long-term management of these patients.

Antiarrhythmic agents: drug interactions of clinical significance.

The management of cardiac arrhythmias has grown more complex in recent years. Despite the recent focus on nonpharmacological therapy, most clinical arrhythmias are treated with existing antiarrhythmics. Because of the narrow therapeutic index of antiarrhythmic agents, potential drug interactions with other medications are of major clinical importance. As most antiarrhythmics are metabolised via the cytochrome P450 enzyme system, pharmacokinetic interactions constitute the majority of clinically significant interactions seen with these agents. Antiarrhythmics may be substrates, inducers or inhibitors of cytochrome P450 enzymes, and many of these metabolic interactions have been characterised. However, many potential interactions have not, and knowledge of how antiarrhythmic agents are metabolised by the cytochrome P450 enzyme system may allow clinicians to predict potential interactions. Drug interactions with Vaughn-Williams Class II (beta-blockers) and Class IV (calcium antagonists) agents have previously been reviewed and are not discussed here. Class I agents, which primarily block fast sodium channels and slow conduction velocity, include quinidine, procainamide, disopyramide, lidocaine (lignocaine), mexiletine, flecainide and propafenone. All of these agents except procainamide are metabolised via the cytochrome P450 system and are involved in a number of drug-drug interactions, including over 20 different interactions with quinidine. Quinidine has been observed to inhibit the metabolism of digoxin, tricyclic antidepressants and codeine. Furthermore, cimetidine, azole antifungals and calcium antagonists can significantly inhibit the metabolism of quinidine. Procainamide is excreted via active tubular secretion, which may be inhibited by cimetidine and trimethoprim. Other Class I agents may affect the disposition of warfarin, theophylline and tricyclic antidepressants. Many of these interactions can significantly affect efficacy and/or toxicity. Of the Class III antiarrhythmics, amiodarone is involved in a significant number of interactions since it is a potent inhibitor of several cytochrome P450 enzymes. It can significantly impair the metabolism of digoxin, theophylline and warfarin. Dosages of digoxin and warfarin should empirically be decreased by one-half when amiodarone therapy is added. In addition to pharmacokinetic interactions, many reports describe the use of antiarrhythmic drug combinations for the treatment of arrhythmias. By combining antiarrhythmic drugs and utilising additive electrophysiological/pharmacodynamic effects, antiarrhythmic efficacy may be improved and toxicity reduced. As medication regimens grow more complex with the aging population, knowledge of existing and potential drug-drug interactions becomes vital for clinicians to optimise drug therapy for every patient.

Effect of phenytoin on the clinical pharmacokinetics of amiodarone.

Five healthy male volunteers were given oral amiodarone hydrochloride, 200 mg per day for 6 1/2 weeks, to determine its effects on the pharmacokinetics of both intravenous and oral phenytoin. Predose amiodarone and N-desethylamiodarone serum concentrations were obtained weekly during weeks 2-6. Amiodarone serum concentrations (ASC) increased during weeks 2-4 and then decreased sharply during weeks 5-6 when oral phenytoin, 2-4 mg/kg/day, was co-administered. In addition, N-desethylamiodarone serum concentrations (DEASC) exceeded corresponding ASC during weeks 5-6 whereas during weeks 2-4, DEASC were less than ASC. Because of the long elimination half-life for amiodarone previously reported in healthy volunteers after single doses of amiodarone and the frequent administration of amiodarone associated with this half-life, a modified equation for a continuous infusion was used to describe each subject's ASC versus time data. Pre-phenytoin ASC were fitted to an appropriate function to predict ASC during weeks 5-6 assuming no interaction. Observed versus predicted ASC were compared for weeks 5 and 6. Observed ASC during weeks 5 and 6 were (mean +/- SD) 0.25 +/- 0.09 micrograms/mL and 0.19 +/- 0.07 micrograms/mL, respectively. Corresponding predicted ASC were 0.36 +/- 0.12 micrograms/mL (P = .011) and 0.38 +/- 0.13 micrograms/mL (P = .004). These represented percent differences of 32.2 +/- 12.5% and 49.3 +/- 5.6% for weeks 5 and 6, respectively. Assuming there were no changes in the bioavailability of amiodarone during continuous administration, these findings strongly suggest induction of amiodarone metabolism by phenytoin. The clinical significance of this interaction remains to be determined.

Effects of coadministration of propafenone on the pharmacokinetics of digoxin in healthy volunteer subjects.

Previous reports have suggested an interaction between propafenone and digoxin. We investigated the pharmacokinetics of IV digoxin when given alone (Phase I), after pretreatment with propafenone 150 mg every 8 hours for seven days (Phase II), and after propafenone 300 mg every 8 hours for 7 days (Phase III). The total body clearance of digoxin during Phase I was 2.45 ml/min/kg and was 2.17 ml/min/kg during Phase II (NS) and decreased to 1.92 ml/min/kg during Phase III (P less than 0.05). The renal clearance and half-life of digoxin were not significantly altered by propafenone. There was a trend towards a decrease in the volume of distribution of digoxin from 9.43 L/kg in Phase I, to 9.33 L/kg in Phase II, and 8.02 L/kg in Phase III. Similarly there was a trend towards a decreased nonrenal clearance of digoxin from 1.21 ml/min/kg during Phase I to 1.01 ml/min/kg during Phase II and to 0.75 ml/min/kg during Phase III. The changes in volume of distribution and nonrenal clearance parallel each other resulting in no change in the elimination half-life of digoxin. It is postulated that the mechanism of this interaction is due to decreases in the volume of distribution and nonrenal elimination of digoxin by propafenone. The degree of this interaction was related to the dose of propafenone. The magnitude of this interaction may be greater in patients and, thus, may require a reduction in the digoxin dose.

Arizona experience with CardioWest Total Artificial Heart bridge to transplantation.

BACKGROUND: We hypothesized that bridge to transplantation with the CardioWest Total Artificial Heart would succeed in a large percentage of patients. Further, we hypothesized that this success rate would not be significantly decreased by infection or thromboembolism. METHODS: From 1993 to March 1999, 24 patients received implants with the intention of bridge to transplantation. Data were collected prospectively. Heparin, coumadin, aspirin, ticlopidine, dipyridamole, and pentoxifylline were used for anticoagulation. RESULTS: Four patients died while on device support. Nineteen of 23 patients (83%) were transplanted. All 19 survived long term. One patient remains on CardioWest Total Artificial Heart support 6 weeks after implant. There was one stroke on the day of transplantation. There was a second stroke on the day of implantation. Neither stroke caused significant residual deficits. Both were in close relationship to an operative procedure. There were no serious device-related infections. CONCLUSIONS: The CardioWest Total Artificial Heart salvaged 20 of 24 critically ill patients. Neither infections nor neurologic problems were significant. We believe it is the device of choice for decompensating patients with biventricular failure who have adequate body and heart size.

Comparison of the CardioWest total artificial heart, the novacor left ventricular assist system and the thoratec ventricular assist system in bridge to transplantation.

BACKGROUND: Device selection has historically been supported by minimal comparative data. Since 1994, we have implanted 43 patients with the CardioWest Total Artificial Heart (CW), 23 with the Novacor Left Ventricular Assist System (N), and 26 with the Thoratec Ventricular Assist System (T). This experience provides a basis for our device selection criteria. METHODS: We reviewed retrospectively the results for survival, stroke, and infection in the CW, N, and T groups. Statistical methods included the Student's t-test, chi2 analysis, and Kaplan-Meier actuarial survival curves. RESULTS: The T group patients were younger and smaller sized than the CW or N group. The CW group had the highest mean central venous pressure (CVP) and lowest mean cardiac index. Survival to transplantation was 75% for CW, 57% for N, and 38% for T. Multiple organ failure postimplant caused most deaths in the CW and T groups. Right heart failure and stroke caused most N deaths. Linearized stroke rates (event/patient-month) were 0.03 for CW, 0.28 for N, and 0.08 for T. Serious infections were found in 20% of CW, 30% of N, and 8% of T patients, but linearized rates showed little difference and death from infection was rare. CONCLUSIONS: The N device should be used in "stable" patients with body surface area (BSA) greater than 1.7 m2 and with minimal right heart failure. Unstable patients with biventricular failure should receive a CW if the BSA is greater than 1.7 m2 or a T if they are smaller.

Pharmacokinetics and pharmacodynamics of intravenous agents for ventricular arrhythmias.

Although no antiarrhythmic agent has ideal pharmacokinetic and pharmacodynamic characteristics, it is useful to evaluate antiarrhythmic agents in terms this ideal profile. The most desirable characteristics of an intravenous antiarrhythmic agent for treating ventricular arrhythmias are outlined. The basic pharmacokinetic and pharmacodynamic properties of the most commonly used agents for this indication-including amiodarone, bretylium, lidocaine, procainamide, and quinidine-are also reviewed, in light of this profile.

Clinical efficacy of amiodarone.

OBJECTIVES: To review the clinical efficacy and role of amiodarone in the management of supraventricular and ventricular arrhythmias and its effects on mortality. METHODS: Review of relevant studies and reports. RESULTS: Amiodarone exerts significant effects on atrial tissue. In most studies it was completely or partly effective in preventing recurrences of atrial fibrillation or flutter in up to 80% of patients. Amiodarone may be superior to class Ia agents for maintaining normal sinus rhythm. Large randomized trials indicate that it is a potent suppressor of ventricular arrhythmia and reduces arrhythmic death after myocardial infarction. In patients with cardiomyopathy, it suppresses asymptomatic arrhythmias and increases left ventricular ejection fraction. Meta-analysis of relevant studies indicated that amiodarone reduces the risk of arrhythmic and sudden death by 29% in high-risk patients with recent myocardial infarction or congestive heart failure. This translates into an overall 13% reduction in total mortality. CONCLUSION: Because of its effectiveness against a broad range of arrhythmias, amiodarone is a valuable addition to the antiarrhythmic pharmacopeia.

Selective stability-indicating high-performance liquid chromatographic assay for recombinant human regular insulin.

This report presents a selective HPLC assay capable of separating recombinant human regular insulin from insulin decomposition and transformation products. The assay utilizes an isocratic delivery of mobile phase, a C18 peptide column, UV detection and is performed at ambient temperature. The standard curve ranges from 0.2 to 2.5 U/ml. The inter-day and intra-day variabilities are less than 7 and 5%, respectively, at the concentrations studied. The accuracy and precision are within 5% over the range of the standard curve.

The CardioWest total artificial heart as a bridge to transplantation.

The CardioWest total artificial heart (TAH), formerly known as the Jarvik-7 and then the Symbion heart, is the only TAH in current clinical use. A new study, approved by the Food and Drug Administration (FDA), was initiated in 1993 with the goal of approving this pump for commercial release. Since then, 145 CardioWest TAHs have been implanted, including 37 pumps in 36 patients at our center. Our 36 patients were studied prospectively according to the investigational device exemption protocol approved by the FDA. Clinical and hemodynamic data obtained upon patients' entry into the study identified this group as mortally ill. After receiving a CardioWest TAH, 29 of the 36 patients (81%) survived to heart transplantation, and 26 (72% of the total group and 90% of the transplant recipients) have survived for up to 7 years (average, 24 months). Multicomponent anticoagulation, based on readily available tests, and the intrinsic properties of the TAH have resulted in a low linearized stroke rate of 0.48 event per patient-year. There have been no device-related mediastinal infections. In dying patients with nonexistent or severely compromised biventricular function, the CardioWest TAH has proved safe and effective, allowing a 72% survival rate for an average of 24 months.

Toxic effects of drugs used in the ICU. Antiarrhythmic agents.

Supraventricular and ventricular arrhythmias remain relatively commonplace in the ICU. Proper pharmacologic treatment requires that the clinician recognize accompanying disease states that may alter the pharmacokinetics and pharmacodynamics of antiarrhythmic drugs. In addition, knowledge of cardiovascular toxicity, noncardiovascular adverse effects, and drug-drug interactions are necessary to optimize antiarrhythmic drug therapy.

Effect of epinephrine on survival after cardiac arrest: a systematic review and meta-analysis.

The use of epinephrine is currently recommended as a treatment option for patients with cardiac arrest. The primary objective of this systematic review was to determine if epinephrine use during cardiac arrest is associated with improved survival to hospital discharge. MEDLINE, EMBASE, The Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, International Pharmaceutical Abstracts, and Biological Abstracts (BIOSIS Previews), and bibliographies of previous systematic reviews. Studies involving patients with cardiac arrest that compared epinephrine to no epinephrine (or placebo) with regard to survival to hospital discharge or 30-day survival. Randomized controlled trials (RCTs) and observational studies were included. The results were stratified into three groups: 1) RCTs, 2) observational studies with unadjusted data (observational-U), and 3) observational studies with adjusted data using multivariate analysis (observational-A). There were a total of 10 studies included in the systematic review and nine studies were included in the meta-analysis. The association between epinephrine use and survival to hospital discharge, grouped by study type was not significant for RCTs (OR 2.33, 95% CI 0.85 to 6.40; p=0.10; I2=0.00%) or observational-U studies (OR 1.17, 95% CI 0.67 to 2.07; p=0.58; I2=76.68%). But epinephrine was associated with decreased survival in observational-A studies (OR 0.43, 95% CI 0.40 to 0.48; P<0.01; I2=0.00%). Epinephrine use during cardiac arrest is not associated with improved survival to hospital discharge. Observational studies with a lower-risk for bias suggest that it may be associated with decreased survival.