A rapid and sensitive liquid chromatography/tandem mass spectrometry assay for simultaneous quantitation of disopyramide and its major metabolite, mono-isopropyl-disopyramide, in rat plasma and its application to a pharmacokinetic study.

Disopyramide as an antiarrhythmic agent has been used for treating ventricular tachycardia and metabolized into its major metabolite, mono-isopropyl-disopyramide, by CYP3A4. We developed a novel, selective, highly sensitive, accurate, rapid method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of disopyramide and mono-isopropyl-disopyramide in rat plasma. This study is the first report for the assay validation using LC-MS/MS in biological fluids after simple protein-precipitation method. The most sensitive signals by multiple reaction monitoring (MRM) showed at m/z 340.2 → 239.2 and 298.2 → 239.2 with same fragment ion for disopyramide and mono-isopropyl-disopyramide, respectively. The lower limit of quantification (LLOQ) was determined at 2 ng/mL for both analytes and the linear concentration ranges were found to be 2-2000 ng/mL for disopyramide and 2-1000 ng/mL for mono-isopropyl-disopyramide. Finally, this assay was successfully applied to pharmacokinetic analysis of disopyramide and mono-isopropyl-disopyramide after oral and intravenous administration of disopyramide.

The mechanism of drug interactions of a selected antiarrhythmic drug with metformin, in different animal models

ABSTRACT This study was carried out to understand the influence of a selected antiarrhythmic drug on the pharmacodynamics and pharmacokinetics of an antidiabetic drug in animal models. Pharmacodynamic and pharmacokinetic responses were determined by measurements of blood glucose and serum insulin and serum metformin to drug interactions between disopyramide and metformin. Single dose and multi dose studies showed that the maximum blood glucose reductions in normal and diabetic rats were at the 6th hour, and in rabbits at the 3rd hour. Glucose-insulin homeostasis was evaluated to assess the safety and effectiveness of the combination. There was a marginal increase in the pharmacokinetic parameters of metformin with multiple dose treatments of disopyramide but no significant changes in kinetic parameters between single and multiple dose studies, compared to metformine alone. There may be a possibility of disopyramide and metformin interaction at the excretion stage, or an additive pharmacodynamic action. This study validates the drug interaction in two dissimilar species, which indicates more probability of its occurrence in humans.

Disopyramide and mianserin intoxication: a unique fatal case--review of the literature.

Lethal occurrence is exceptional after disopyramide or mianserin poisoning. A case of intentional lethal intoxication with these drugs was reported, as well as a review of the literature. Pre- and postmortem blood concentrations of disopyramide or mianserin were assessed in a woman who died from acute cardiac failure after ingestion. The premortem blood concentration of disopyramide alone was considered lethal, and a toxic premortem concentration of mianserin was observed that may have increased cardiovascular failure induced by disopyramide because the metabolism of both drugs is mediated via cytochrome P450. Moreover, it was shown that the postmortem redistribution of disopyramide was limited, as pre- and postmortem concentrations were 48 and 65 mg/L, respectively. As regards mianserin, redistribution was observed after death with pre- and portmortem concentrations at 0.23 and 0.79 mg/L, respectively. This case illustrates that if postmortem blood concentration of disopyramide is known, the premortem concentration can be deduced.

Effects of serum concentrations of disopyramide and its metabolite mono-N-dealkyldisopyramide on the anticholinergic side effects associated with disopyramide.

The aim of this study was to evaluate the relationship between the anticholinergic side effects associated with disopyramide (DP) and serum DP or mono-N-dealkyldisopyramide (MND) concentrations and the safety range of DP or MND for prevention of anticholinergic side effects in 141 inpatients. The serum DP and MND concentrations were determined by high-performance liquid chromatography. No correlation was observed between creatinine clearance (Ccr) and the ratio of the serum concentration to the dose (C/D) of DP, but a significant inverse correlation was observed between Ccr and the C/D of MND. It was observed that the ratio of MND concentration to DP concentration in the group, whose Ccr was below 20 ml/min, was higher than that of the other groups. Although no significant difference was observed in the DP concentration between the patients without (Group 1) or with (Group 2) anticholinergic side effects, significant differences were observed in the MND concentration, Ccr, and the ratio of MND/DP. The DP concentrations of both Groups 1 and 2 were distributed from 0.13 to about 5 microg/ml. On the other hand, although the MND concentrations of Group 1 were below about 1 microg/ml, the MND concentrations of Group 2 were above about 1 microg/ml. These results suggest that not only DP concentration but also MND concentration should be monitored in patients whose renal function is decreased to prevent anticholinergic side effects associated with DP, and that when serum MND concentration was over approximately 1 microg/ml, the dose should be decreased or discontinued.

Population pharmacokinetic investigation of disopyramide by mixed effect modelling using routine clinical pharmacokinetic data in Japanese patients.

OBJECTIVE: To estimate the population pharmacokinetic parameters of disopyramide using non-linear mixed effects modelling. METHOD: A total of 148 serum levels from 109 patients (61 males and 48 females) receiving disopyramide were collected. RESULTS: The final pharmacokinetic model was Cl (L/h)=3.75.TBW0.567.AGE-0.374.Conc(-0.719).1.48(DOSE>or=5), Vd (L/kg)=4.13 and k(a) (h-1)=0.363, where Cl is total body clearance, Vd is apparent volume of distribution, k(a) is absorption rate constant, TBW is total bodyweight (kg), AGE is age (years), Conc is the concentration of disopyramide (microg/mL), and DOSE>or=5=1 for patient received 5 mg/kg/day of disopyramide dosage or over and 0 otherwise. CONCLUSION: Application of the findings in this study to patient care may permit selection of an appropriate initial maintenance dosage to achieve target disopyramide concentrations and the desired therapeutic effect.

Toxic interactions between fluconazole and disopyramide in chick embryos.

The present study evaluated the effect of fluconazole on the heart, as well as and the toxic interactions between fluconazole and disopyramide in chick embryos. Chick embryos have been widely used in pharmacologic and toxicologic experiments for evaluating drug action. Fertilized eggs of White Leghorns were incubated and investigated. Fluconazole 0.4 mg/egg, 0.8 mg/egg, 1.2 mg/egg alone or disopyramide 0.3 mg/egg alone was injected into the air sac of each fertilized egg. And fluconazole 0.4 mg/egg with disopyramide 0.3 mg/egg was injected into the air sac of each fertilized egg. Electrocardiograms (ECGs) were recorded 0 to 60 min after the drug injection, and heart rate was determined from ECG wave cycles. Changes in heart rate were expressed as mean-percent changes of the drug-treated groups to the matched control. After the administration of fluconazole 0.4 mg/egg alone, the heart rate did not differ compared with that of the controls. However, the heart rate was significantly decreased with the administration of fluconazole 0.8 mg/egg and 1.2 mg/egg. The heart rate was also significantly decreased by the administration of fluconazole 0.4 mg/egg together with disopyramide 0.3 mg/egg. In addition, an arrhythmia was produced by fluconazole and disopyramide. These findings indicate that the interaction between fluconazole and disopyramide has a marked influence on the heart rate in chick embryos.

Human organic cation transporter 3 mediates the transport of antiarrhythmic drugs.

Antiarrhythmic drugs have been considered to be transported by the organic cation transport system. The purpose of this study was to elucidate the molecular mechanism underlying the transport of antiarrhythmic drugs using cells from the second segment of the proximal tubule (S2) cells of mice expressing human-organic cation transporter 3 (S2 human-OCT3). The antiarrhythmic drugs tested were cibenzoline, disopyramide, lidocaine, mexiletine, phenytoin, pilsicanide, procainamide and quinidine. Human-OCT3 mediated a time- and dose-dependent uptake of quinidine and lidocaine, with Km values of 216 and 139 microM, respectively. Human-OCT3 also mediated the uptake of disopyramide and procainamide but not that of phenytoin. All antiarrhythmic drugs tested inhibited histamine uptake mediated by human-OCT3 in a dose-dependent manner. The IC50 values of antiarrhythmic drugs for human-OCT3 ranged between 0.75 and 656 microM. Kinetic analysis revealed that disopyramide, lidocaine, procainamide and quinidine inhibited histamine uptake mediated by human-OCT3 in a competitive manner. In conclusion, these results suggest that human-OCT3 mediates the transport of antiarrhythmic drugs, which may be the mechanism underlying the distribution and the elimination of these drugs.

Role of biantennary glycans and genetic variants of human alpha1-acid glycoprotein in enantioselective binding of basic drugs as studied by high performance frontal analysis/capillary electrophoresis.

PURPOSE: To establish a clear understanding of the role of biantennary branching glycans and genetic variants of alpha1-acid glycoprotein (AGP) in enantioselective bindings of basic drug. METHODS: Human native AGP was separated using concanavalin A affinity chromatography into two subfractions, the unretained fraction (UR-AGP, defect of biantennary glycan) and the retained fraction (R-AGP, possessing biantennary glycan(s)). Imminodiacetate-copper (II) affinity chromatography was used to separate human native AGP into A variant and a mixture of F1 and S variants (F1*S variants). The mixed solutions of the (R)- or (S)-isomer of the model drugs (15 microM disopyramide (DP) or 30 microM verapamil (VER)) and 40 microM of respective AGP species were subjected to high-performance frontal analysis/capillary electrophoresis (HPFA/CE) to determine the unbound drug concentrations. RESULTS: The unbound concentrations (Cu) of DP in UR-AGP solutions were lower than those in R-AGP solutions, whereas there was no significant difference in the enantiomeric ratios (Cu(R)/Cu(S)) of DP between UR- and R-AGP solutions. In case of genetic variant, the Cu(R)/Cu(S) values of DP in F1*S and A solutions were 1.07 and 2.37, respectively. On the other hand, the enantiomeric ratio of VER in F1*S and A variant solutions were 0.900 and 0.871, respectively. CONCLUSIONS: The biantennary glycan structures are related to binding affinity of DP to AGP, but not responsible for the enantioselectivity. Genetic variants give significant effect on the enantioselectivity in DP binding, but not in VER binding.

Population pharmacokinetics, protein binding and antiarrhythmic effects of disopyramide enantiomers in arrhythmic patients.

Disopyramide (DP) is widely used as an antiarrhythmic agent. The antiarrhythmic effects of its enantiomers differ from each other and its metabolism and protein binding are also stereoselective. Population pharmacokinetic parameters of DP racemate, enantiomers (S(+)-DP, R(-)-DP), and their unbound concentrations (uDP, S(+)-uDP and R(-)-uDP) were analyzed using the nonlinear mixed effect model (NONMEM) program. Data were available from 108 points of 33 arrhythmic patients on maintenance therapy with DP racemate. We evaluated the factors to which pharmacokinetic parameters are attributed and the relationships between each serum concentration and the antiarrhythmic effect. A one-compartment model was fitted to the data using NONMEM. For DP, S(+)-DP and R(-)-DP, elimination rate constants (kes) were estimated as 0.0648, 0.0663 and 0.0691/h, respectively and the mean apparent volume of distribution (Vd/F) were estimated as 63.2, 54.1 and 71.6 l, respectively. Using the ke and Vd/F values estimated by NONMEM, time-concentration curves were well fitted to the observed data. Unbound fractions of both DP enantiomers showed nonlinearity and the binding ratio of S(+)-DP was 0.84 +/- 0.07, which was higher than that of R(-)-DP [0.70 +/- 0.11 (p < 0.01)]. Unbound fractions of both DP enantiomers correlated with alpha1-acid glycoprotein (AGP) (p < 0.01). On the other hand, using NONMEM, a significant proportion of the variability of Vd/F could be attributed only to AGP (p < 0.001). NONMEM was able to clarify the pharmacokinetic features in the protein binding of DP. Individual steady state concentrations were estimated by NONMEM using the Bayesian method. The average unbound concentrations of all nine responders were higher than those of the four non-responders, even though this difference was not significant. Unbound concentrations may reflect drug concentrations in the tissue, which suggests that these concentrations may indicate an antiarrhythmic effect rather than the total concentration.

Stereoselective pharmacokinetics and pharmacodynamics of disopyramide and its metabolite in rabbits.

The extent to which interactions between enantiomers of disopyramide and between disopyramide and its metabolite, mono-N-dealkylated disopyramide (MND), contribute to stereoselectivity of the anti-arrhythmic effect has been investigated in rabbits by measuring the prolongation of the QUc interval. The plasma unbound fraction of disopyramide enantiomers was constant at a concentration range of 1.44-28.9 microM. An intravenous infusion study of the disopyramide enantiomer or racemate suggested that the S-enantiomer had a pharmacological effect, determined by linear regression analysis, approximately 3.3-times more potent than that of the R-enantiomer. Furthermore, the effect caused by racemic disopyramide was the sum of that elicited by both enantiomers individually. No significant difference was observed between the slope of linear regression analysis of intravenous infusion and that of intravenous bolus injection. Single intravenous bolus injection of MND did not affect the QUc intervals. In conclusion, the S-enantiomer of disopyramide was approximately 3.3-times more potent pharmacologically than the R-enantiomer. The relationship between plasma concentration of the disopyramide enantiomers and pharmacological effect was the sum of each enantiomer individually.

Bioavailability assessment of disopyramide using pharmacokinetic-pharmacodynamic (PK-PD) modeling in the rat.

The relationship between the serum concentration and the pharmacological effect of disopyramide was investigated quantitatively to estimate the extent of its oral bioavailability (EBA(p.o.) and to evaluate the drug interaction with miconazole, a CYP3A4 inhibitor. An integrated pharmacokinetic-pharmacodynamic (PK-PD) model was used to describe the relationship between the serum concentrations and changes in QT interval (pharmacological data) of disopyramide after intra-vascular infusion for 15 min (i.v. short-term infusion) to rats. A two-compartment model was applied to the pharmacokinetics of disopyramide. The pharmacological data after short-term infusion were well explained using a PK-PD link model. To validate the present PK-PD model. disopyramide was administered intra-vascularly in separate experiments, and the doses were predicted only from the pharmacological data. The model predicted doses were identical to the actual doses, regardless of the dosing rates. This result indicates that the PK-PD model used in the present study is appropriate, and that the relationship between the serum concentrations and changes in QT intervals is independent of the dosing (input) rate. When miconazole was co-administered orally 1 h before disopyramide infusion, the serum disopyramide concentrations were significantly higher than that following disopyramide alone. The raised serum concentrations under miconazole co-administration were well explained by nonlinear elimination clearance. The pharmacological effects of disopyramide under miconazole co-administration, were also greater than those following disopyramide alone. The results of the PK-PD analysis indicated that the enhanced pharmacological response under miconazole co-administration was simply caused by a pharmacokinetic change. The EBA(p.o.) values estimated from the pharmacological effects predicted the observed values reasonably well. In conclusion, we demonstrated following: (1) the pharmacological effect after intra-vascular administration of disopyramide is related quantitatively to the serum concentrations using a PK-PD model; (2) miconazole affects only the elimination clearance of disopyramide to enhance the pharmacological effect; (3) the EBA of disopyramide can estimated reasonably only well from the pharmacological data using the PK-PD model; (4) there is no dosing-rate-dependent or dosing-route-dependent pharmacological effect of disopyramide.

Potentially fatal interaction between azithromycin and disopyramide.

A patient on disopyramide developed disopyramide toxicity when treated concurrently with azithromycin. Evidence of toxicity included an elevated serum disopyramide level and ventricular tachycardia requiring cardioversion. The azalide antibiotic presumably inhibited dealkylation of disopyramide to its major metabolite, mono-N-dealkyldisopyramide. Physicians should avoid using azithromycin in patients on disopyramide. If this drug combination is unavoidable, disopyramide levels must be closely monitored.

Enantioselective analysis of disopyramide and mono-N-dealkyldisopyramide in plasma and urine by high-performance liquid chromatography on an amylose-derived chiral stationary phase.

An enantioselective high-performance liquid chromatography method was developed for the simultaneous determination of disopyramide (DP) and mono-N-dealkyldisopyramide (MND) enantiomers in plasma and urine. The drugs were extracted from plasma samples by liquid-liquid extraction with dichloromethane after protein precipitation with trichloroacetic acid; the urine samples were processed by liquid-liquid extraction with dichloromethane. The enantiomers were resolved on a Chiralpak AD column using hexane-ethanol (91:9, v/v) plus 0.1% diethylamine as the mobile phase and monitored at 270 nm. Under these conditions the enantiomeric fractions of the drug and of its metabolite were analyzed within 20 min. The extraction procedure was efficient in removing endogenous interferents and low values for the relative standard deviations were demonstrated for both within-day and between-day assays. The method described in this paper allows the determination of DP and MND enantiomers at plasma levels as low as 12.5 ng/ml and can be used in clinical pharmacokinetic studies.

Clinical pharmacokinetics and effects of an oral sustained-release preparation of disopyramide prescribed for patients undergoing maintenance hemodialysis.

AIMS: We evaluated the clinical pharmacokinetics of a sustained-release preparation of disopyramide phosphate (DSR) and its effects on supraventricular arrhythmias in hemodialysis patients. METHODS: Eight hemodialysis patients with either paroxysmal supraventricular tachycardia (PSVT) or PSVT plus paroxysmal atrial fibrillation (Paf) were given 150 mg of DSR 2 h before each hemodialysis. The frequency of PSVT, the duration of Paf before and 2 weeks after starting DSR and the blood concentration of the drug were evaluated. RESULTS: There was no significant difference between serum levels of DSR before and after hemodialysis. The frequency of PSVT and the duration of Paf were significantly reduced by the therapy. Side effects and electrocardiographic abnormalities did not appear during the period. CONCLUSION: We conclude that hemodialysis does not remove DSR, and that a single dose of 150 mg of DSR given 2 h before hemodialysis is safe and sufficient to reduce the incidence of supraventricular arrhythmias.

Dispersion of filtered P wave duration by P wave signal-averaged ECG mapping system: its usefulness for determining efficacy of disopyramide on paroxysmal atrial fibrillation.

INTRODUCTION: Although it is desirable to know drug efficacy before initiating antiarrhythmic therapy, there have been no methods for this evaluation. P wave signal-averaged ECG (P-SAECG) is useful to detect subtle changes in disturbance of atrial conduction. The purpose of this present study was to test whether P-SAECG mapping system would give any information on the efficacy of disopyramide on the prevention of paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: P-SAECG was performed before disopyramide treatment, at 3 hours after a single dose of oral disopyramide (200 mg), and after 4 weeks of disopyramide treatment (300 mg/day). After measuring the filtered P wave duration by the vector magnitude and mapping methods, we calculated filtered P wave duration dispersion, difference between the maximal and minimal filtered P wave duration within 16 chest leads at these three time points. Filtered P wave duration and filtered P wave duration dispersion before treatment were longer in 32 patients with symptomatic PAF than in 31 healthy volunteers. Disopyramide was effective for suppression of PAF in 17 patients and ineffective in 15 patients after 4 weeks of treatment. Filtered P wave duration was similarly prolonged at 3 hours in the two groups, whereas filtered P wave duration dispersion at 3 hours after the disopyramide administration behaved differently; it decreased in all of the effective group and increased in all of the ineffective group. The effective patients were prospectively followed with the same treatment for 6 months. In 16 (94%) of these 17 effective patients, no PAF was documented and they remained to be asymptomatic. CONCLUSIONS: Thus, measuring filtered P wave duration dispersion with the P-SAECG mapping method after a single administration may predict the long-term efficacy of disopyramide in patients with PAF.

Pharmacodynamic analysis of the electrocardiographic interaction between disopyramide and erythromycin in rats.

Disopyramide (DP) is known to induce QT prolongation and Torsades de Pointes (TdP) when administered concomitantly with erythromycin (EM). To define and evaluate quantitatively the arrhythmogenic risk of the concomitant administration of DP and EM, we investigated the influence of EM on the pharmacokinetics and pharmacodynamics of DP in rats. The time profiles of change in QT interval and plasma concentration of each drug were evaluated during and after constant intravenous infusion of DP (6.0 or 15.0 mg/kg/h), EM (4.0 or 8.0 mg/kg/h), and coadministration of DP and EM (DP 6.0 mg/kg/h plus EM 4.0 mg/kg/h). Each agent induced QT prolongation at plasma concentrations within the therapeutic range in humans. DP-induced QT prolongation was proportional to its plasma concentration. In the case of EM, the Emax model with an "effect compartment" could explain the relationship between plasma EM concentrations and changes in QT interval. Although coadministration of EM with DP gave enhanced QT prolongation compared to dosing with DP alone, EM did not affect the pharmacokinetics of DP. In conclusion, it was shown that a pharmacodynamic interaction contributes to the electrocardiographic adverse reaction (i.e., QT prolongation) induced by coadministration of DP and EM in rats.

Enantioselective tissue distribution of the basic drugs disopyramide, flecainide and verapamil in rats: role of plasma protein and tissue phosphatidylserine binding.

PURPOSE: The stereoselective distribution of three basic drugs, disopyramide (DP), flecainide (FLC) and verapamil (VP), was studied to clarify the relationship between the tissue-to-unbound plasma concentration ratio (Kpf) and drug lipophilicity and binding to phosphatidylserine phs), which are possible factors determining the tissue distribution of these drug enantiomers. METHODS: The drug enantiomer or racemate was administered to rats by intravenous constant infusion. Their concentrations in plasma and tissues were determined using enantioselective high-performance liquid chromatography. Plasma protein binding, and buffer-octanol and buffer-hexane containing PhS partition coefficients were also determined. RESULTS: The stereoselectivity of the tissue-to-plasma concentration ratio (Kp) was partly associated with that of serum protein binding. However, the Kpf value of R(+)-VP in the lung was significantly higher than that of S(-)-VP. A linear correlation was observed between the Kpf values of these drug enantiomers in brain, heart, lung and muscle, and their buffer-hexane containing PhS partition coefficients. The in vitro data for the binding of these drugs to PhS suggest that stereoselective binding of VP to PhS may correspond to its stereoselective tissue binding. CONCLUSIONS: Our findings provide some evidence for a role of tissue PhS in the tissue distribution of basic drugs with respect to stereoselectivity of drug enantiomers distribution.

Quantitative determination of disopyramide, verapamil and flecainide enantiomers in rat plasma and tissues by high-performance liquid chromatography.

Enantiomers of disopyramide (DP), flecainide (FLC) and verapamil (VP) were extracted from rat plasma and tissues (brain, lung, heart, liver, kidney and muscle), followed by quantitative determination using enantioselective high-performance liquid chromatography with chiral stationary-phase columns. The recoveries of S-(+)- and R-(-)-DP from tissues were higher than 69%, and the within- and between-day coefficients of variation were very low (0.5 - 5.7%). The lower limits of detection in each tissue were less than 289 ng/g tissue. The recoveries of S-(+)- and R-(-)-FLC from tissues were higher than 88%, and the within- and between-day coefficients of variation were 1.2-6.0%. The lower limits of detection in each tissue were less than 37 ng/g tissue. The recoveries of S-(-)- and R-(+)-VP from tissues were higher than 80%, and the within- and between-day coefficients of variation were 0.5-6.2%. The lower limits of detection in each tissue were less than 51 ng/g tissue. The analytical methods established in this study will be suitable for determining the concentrations of the enantiomers of these anti-arrhythmic agents in rat plasma and tissues.

Percutaneous absorption of disopyramide, lidocaine and trimecaine.

Promoting effect of cyclic monoterpenes on percutaneous absorption of antiarrythmics drugs disopyramide, lidocaine and trimecaine was investigated in the rats. Laurocapram (Azone) was used as a standard comparator of penetration enhancement. The absorption of trimecaine was significantly enhanced by addition of limonene, trans-p-menthane and Azone in 1% concentration. Lidocaine and disopyramide penetrated across the skin only when 1% of limonene was used. Other cyclic monoterpenes showed no effect on percutaneous absorption of examined drugs.