Determination of fendiline and gallopamil by capillary isotachophoresis.

Capillary isotachophoresis was applied for the determination of fendiline and gallopamil--calcium antagonists--in serum. The cationic electrolyte system containing Na+ with acetic acid as a counter constituent was used as a leading electrolyte with the pH 4.7 and the terminating electrolyte was beta-alanine. Most of the proteins were precipitated with methanol, ethanol and dimethylketone. The lowest limits of quantitation were obtained for the pretreatment of serum with methanol. The recoveries of both compounds varied from 91.3 to 97.5%. The relative standard deviations varied from 0.6 to 7.7%.

Straightforward solid-phase extraction method for the determination of verapamil and its metabolite in plasma in a 96-well extraction plate.

Straightforward solid-phase extraction (SPE) methods were developed for the determination of verapamil and its metabolite in a plasma matrix. The spiked plasma sample was pretreated with 2% phosphoric acid followed by two different SPE methods using a Waters Oasis HLB 96-well extraction plate. Recoveries greater than 90% were obtained using both a generic and a selective SPE methods. The generic method is a good starting protocol, and it is applicable to a wide range of compounds. This generic method consists of using 5% methanol as the wash solvent, and 100% methanol for the elution. The limitation of the non-specific method is that it does not remove all plasma constituents that interfere with the quantitation of the metabolite, norverapamil. A second, more specific method was developed using the same Oasis HLB sorbent which removes more plasma interferences and provides cleaner extracts for the HPLC-UV analysis. This selective method uses both the methanol concentration and the pH advantageously to preferentially isolate the analytes of interest from a complex sample matrix. Recoveries of greater than 90% with R.S.D.s less than 3.8% were obtained with this selective method.

Internally standardized simultaneous assay of gallopamil enantiomers in human plasma by means of high performance liquid chromatography.

A high performance liquid chromatographic method with internal analogue standardisation for the simultaneous assay of the gallopamil enantiomers in human plasma after administration of racemic gallopamil is described. The method comprises extraction from alkalinized plasma into an n-hexane/2-propanol phase (95:5), back extraction into 1 N hydrochloric acid and extraction into n-hexane/ 2-propanol (95:5) after addition of 5 N sodium hydroxide. Separation of the optical antipodes was achieved by the use of a chiral phase (Daicel Chiralcel OD-H) and quantification by means of fluorescence detection. A limit of detection of about 0.2 ng/ml was determined for both enantiomers. Under routine conditions the limit of determination (variation coefficient < 20%) was about 0.5 ng/ml for (R)- and (S)-gallopamil. The method is not impaired by the known metabolites. The suitability of the method for clinical pharmacology studies is demonstrated with samples obtained from healthy subjects. First results of kinetic studies in humans showed that the (R)-enantiomer dominates after oral administration of racemic gallopamil.

Effects of gallopamil, a Ca2+ channel blocker in models of ventricular arrhythmia in dogs.

The antiarrhythmic effects of gallopamil on adrenaline-, digitalis- and two-stage coronary ligation-induced arrhythmias and on adrenaline-induced triggered arrhythmia were investigated. Gallopamil suppressed adrenaline-induced and adrenaline-induced triggered arrhythmias, and these antiarrhythmic effects of gallopamil were similar to those of verapamil. Gallopamil also showed some antiarrhythmic effect on the 48-h coronary ligation-induced arrhythmia. The plasma concentration of gallopamil which decreased the arrhythmic ratio for adrenaline-induced arrhythmia by 50% (IC50) was 32 ng/ml. These results indicate that gallopamil may be a clinically useful antiarrhythmic drug.

Enantioselective gallopamil protein binding.

The protein binding of the enantiomers of gallopamil has been investigated in solutions of human serum albumin, alpha 1-acid glycoprotein and serum. Over the range of concentrations attained after oral gallopamil administration, the binding of both enantiomers to albumin, alpha 1-acid glycoprotein, and serum proteins was independent of gallopamil concentration. The binding to both human serum albumin (40 g/liter) [range of fraction bound (fb) R: 0.624 to 0.699; S: 0.502 to 0.605] and alpha 1-acid glycoprotein (0.5 g/liter) (range of fb R: 0.530 to 0.718; S: 0.502 to 0.620) was stereoselective, favoring the (R)-enantiomer (predialysis gallopamil concentrations 2.5 to 10,000 ng/ml). When the enantiomers (predialysis gallopamil concentration 10 ng/ml) were studied separately in drug-free serum samples from six healthy volunteers the fraction of (S)-gallopamil bound (fb: 0.943 +/- 0.016) was lower (P < 0.05) than that of (R)-gallopamil (fb: 0.960 +/- 0.010). The serum protein binding of both (R)- and (S)-gallopamil was unaffected by their optical antipodes (fb R: 0.963 +/- 0.011; S: 0.948 +/- 0.015) indicating that at therapeutic concentrations a protein binding enantiomer-enantiomer interaction does not occur. The protein binding of (R)- and (S)-gallopamil ex vivo 2 h after single dose oral administration of 50 mg pseudoracemic gallopamil (fb R: 0.960 +/- 0.010: predialysis [R] 6.9 to 35.3 ng/ml; S: 0.943 +/- 0.016: predialysis [S] 9.5 to 30.7 ng/ml) was comparable to that observed in vitro in drug-free serum. Gallopamil metabolites formed during first-pass following oral administration, therefore, do not influence the protein binding of (R)- or (S)-gallopamil.

Red blood cell partitioning of gallopamil, verapamil and norverapamil.

In-vitro binding of calcium-antagonists gallopamil and verapamil (and its main metabolite norverapamil) to human red blood cells (RBCs) was investigated. The drugs are bound reversibly and dose dependent to RBCs in the same order of magnitude, with partition-coefficients of kRBC = 0.12-0.34 for gallopamil, kRBC = 0.10-0.30 for verapamil and kRBC = 0.10-0.27 for norverapamil. The data indicate that, although RBCs may act as subcompartments of the blood for this class of compounds, they may have no influence on therapeutic plasma concentrations, due to their low kRBC.

Direct determination of the enantiomeric ratio of verapamil, its major metabolite norverapamil and gallopamil in plasma by chiral high-performance liquid chromatography.

Two methods for the determination of the enantiomeric ratio of verapamil in plasma by high-performance liquid chromatography have been developed. On an alpha 1-acid glycoprotein chiral stationary phase (Chiral-AGP) verapamil was separated after the acetylation of the main metabolite norverapamil, which interferes with the resolution of verapamil. On an amylose tris-3,5-dimethylphenylcarbamate column (Chiralpak AD) verapamil and norverapamil were determined simultaneously without prior derivatization. Gallopamil was separated on both columns under similar conditions.

Determination of gallopamil in human plasma by selected ion monitoring.

A gas chromatographic mass spectrometric procedure using selected ion monitoring is described for the quantification of gallopamil in human plasma. Gas chromatographic separation of gallopamil from phenolic metabolite isomers is made possible by treatment with ethyl chloroformate. The detection limit for the quantitation by the present method is 0.09 ng/ml of plasma. The method has sufficient sensitivity to permit pharmacokinetic studies with human subjects following the oral administration of gallopamil hydrochloride.

[Efficacy and duration of effect of two delayed-action preparations of gallopamil in patients with exercise angina]. / Efficacia e durata di effetto di due formulazioni di gallopamil, pronta e ritardo, in pazienti con angina da sforzo.

In 15 subjects (13 male, 2 female) with reproducible threshold ischaemic effort angina, the efficacy and the duration of the effect of two different formulations of gallopamil in equal doses were evaluated. One of these was gallopamil slow release administered twice daily (at 7.00 a.m. and 6.00 p.m.) in doses of 100 mg. The other was action gallopamil immediate release administered four times daily (at 7.00 a.m., 1.00 p.m., 6.00 p.m., 11.00 p.m.) in doses of 50 mg. The double-blind study followed the cross-over model. After one week of run-in with placebo and two-weeks of treatment with active preparations, the patients underwent a clinical examination, an ambulatory electrocardiogram monitoring for 24 hours and two cycloergometric effort tests. The ergometric tests were carried out at 10.00 a.m. and at 5.00 p.m. on the same day so that there was a three-hour interval between the administration of both preparations (slow release and immediate release) and the morning test. The ergometric test which was carried out at 5.00 p.m. was at a ten-hour interval from the administration of slow release and at a four-hour interval from the administration of immediate release. For each period of treatment the gallopamil plasma concentrations were dosed during the ergometric test. In both these tests, the two preparations significantly increased the duration of the exercise compared to the basal values with placebo (7.9 +/- 2.3 minutes with placebo, 9.2 +/- 2.0 minutes with slow release.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of tolerance after chronic administration of controlled-release isosorbide-5-mononitrate. Interaction of nitrate and gallopamil.

The effect of a controlled-release formulation of isosorbide-5-mononitrate (IS-5-MN) was studied in patients with coronary heart disease (CHD), with the aim of comparing the acute effect with that after chronic administration on parameters of ischemia. To determine whether any tolerance developed, several aspects of ischemia were observed: ECG signs, clinical parameters, and left ventricular function. Fifteen patients with angiographically proven CHD were examined with 12-lead exercise ECG before, 2 h and 4 h after the first dose and after 10 days of therapy with 60 mg IS-5-MN (Coleb-Duriles) once daily. After 7 days, three radionuclide ventriculographies were performed: control, 2 h after nitrate and 2 h after 75 mg gallopamil. Plasma concentrations of IS-5-MN were measured before every exercise test. The results showed a reduction of total ST-segment depression from 0.59 mV to 0.29 mV after 2 h (NS) and 4 h (P less than 0.05) on the 1st day and from 0.48 mV to 0.32 mV (P less than 0.05) and 0.31 mV (NS) after 10 days. The severity of angina pectoris was diminished by about 50%. The effect on exercise duration and time to ST-segment depression by more than 0.1 mV remained unchanged after 10 days, whereas the effect on blood pressure, heart rate and time to onset of angina was attenuated. The mean decrease in ejection fraction (EF) from rest to exercise was reduced from--5.9% to -1.9% (P less than 0.05) after nitrate, while an increase of +1.4% was seen after gallopamil (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of the calcium antagonist gallopamil in man.

The metabolism of gallopamil (5-[(3,4-dimethoxyphenyl)methylamino]-2-(3,4,5-trimethoxyphenyl) -2- isopropylvaleronitrile hydrochloride, Procorum, G) was studied after single administration (2 mg i.v., 50 mg p.o.) of unlabelled and labelled G (14G, 2H). TLC, HPLC, GLC, MS and RIA were used for assessment of G and its metabolites in plasma, urine and faeces. G clearance is almost completely metabolic, with only minimal excretion of unchanged drug. Metabolites represent most of the plasma radioactivity after p.o. administration. They are formed by N-dealkylation and O-demethylation with subsequent N-formylation, or glucuronidation, respectively. Compound A, derived by loss of the 3,4-dimethoxyphenethyl moiety of G is the main metabolite in plasma and urine (about 20% of the dose). This metabolite is accompanied by its N-formyl derivative (C), by the N-demethylated compound (H) and the acid (F), formed by oxidative deamination of A. Only 3 unconjugated monphenoles from several O-demthylated products showed distinct plasma levels which were nevertheless lower than metabolite A. These metabolites had no relevance to the pharmacodynamic action. Conjugated monophenolic and diphenolic products represented the major part in plasma and were excreted predominantly via the bile: they represented almost the whole faecal metabolite fraction. Less than 1% of the dose was recovered unchanged in the urine. About 50% of the dose is excreted by urine and 40% by faeces.

Quantitative determination of verapamil and metabolites in human serum by high-performance liquid chromatography and its application to biopharmaceutic investigations.

A specific and sensitive high-performance liquid chromatographic method for the quantitative analysis of verapamil and N-desmethylverapamil in human serum is described. The analytes were extracted from serum using diethylether under alkaline conditions, followed by back extraction into dilute hydrochlorid acid for chromatographic analysis on a reversed-phase column with a mobile phase consisting of acetonitrile, water and perchloric acid at a flow rate of 1 l/min. The analytes were detected by fluorescence detection, the influence of temperature on retention is discussed. The method is linear, quantitative and reproducible for two calibration ranges in serum (2.5 ng/ml-100 ng/ml and 12.5 ng/ml-500 ng/ml) using peak area ratios analyte/internal standard for quantification. At ultimate sensitivity, concentrations down to 250 pg/ml could be assayed. The method was selective to 6 other metabolites of verapamil and common exogenous interferences. It was applicated to the serum samples of a comparative 120 mg - verapamil hydrochloride tablet single dose two-way cross-over study comprising 18 volunteers. The pharmacokinetic data for both formulations are presented.

Objective evaluation of gallopamil in patients with chronic stable angina. Exercise testing, Holter monitoring, cross-sectional echocardiography and plasma levels.

In this double-blind, randomized placebo-controlled study the effects of two dosages of gallopamil on exercise tolerance were evaluated in 12 patients with stable effort angina. After a pre-study screening aimed at assessing the reproducibility of the exercise response, the patients entered the study which consisted of three 7-day consecutive periods during which placebo or gallopamil 50 mg t.i.d. or gallopamil 75 mg t.i.d. were administered according to a randomized sequence. 24-hour Holter monitoring and cross-sectional echocardiography were performed on the 6th and 7th day of each treatment period, respectively. On the 7th day of each treatment period, patients underwent an exercise test 2 and 8 h after the last administration of gallopamil or placebo. Blood samples for plasma gallopamil concentrations were taken just before each exercise test. The results were analysed using a three-way analysis of variance; intergroup differences were evaluated by the Newman-Keuls test. At 2 h, 11 patients with placebo and three with gallopamil experienced angina; both dosages of gallopamil significantly prolonged exercise time and -1 mm time and also reduced ST segment depression and the rate-pressure product at submaximal workload. No significant change in the rate-pressure product was observed either on the appearance of 1 mm ST depression or at peak exercise. At 8 h, 11 patients with placebo and gallopamil 50 mg t.i.d. and 10 with gallopamil 75 mg t.i.d. experienced angina; although exercise time was significantly prolonged by both dosages of gallopamil, the increase in -1 mm time and reduction of ST segment depression at submaximal workload did not reach statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Gas chromatographic determination of gallopamil and norgallopamil in human plasma.

A highly sensitive gas chromatographic assay is described for the simultaneous determination of gallopamil, a calcium channel blocking agent, and its major metabolite, norgallopamil. A multi-step extraction procedure is employed followed by on-column capillary gas chromatographic analysis using nitrogen-selective detection. Acetylation of norgallopamil is performed to enable accurate quantification of the metabolite. Linearity was achieved over the range 1-50 ng/ml for both analytes. Assay specificity, precision and accuracy were investigated.

[Gallopamil poisoning. Its course and therapy]. / Intoxikation mit Gallopamil. Verlauf und Therapie.

About two hours after swallowing 7 g of Gallopamil, a calcium antagonist, with suicidal intent a 32-year-old woman was admitted to hospital in a somnolent state. At that time the systolic blood pressure was about 40 mm Hg, in the presence of a 3 degrees A-V block. Orciprenaline, dopamine and dobutamine, as well as calcium, proved ineffective. Initially massive doses of adrenaline and noradrenaline, and their continued administration over the subsequent 26 hours, succeeded in normalizing the blood pressure and after transitory pacing, terminated, the arrhythmia in the course of 24 hours. About four hours after its intake the plasma gallopamil concentration was 8.4 micrograms/ml, about 100 times the therapeutic range.

High-performance liquid chromatographic (HPLC) assay using fluorescence detection for the simultaneous determination of gallopamil and norgallopamil in human plasma.

Gallopamil is a calcium-channel antagonist with reported activity in experimental animals three to five times higher than that of verapamil. An automated high-performance liquid chromatographic (HPLC) method with fluorescence detection is described for the simultaneous determination of gallopamil and its metabolite norgallopamil in plasma. Gallopamil was well resolved from norgallopamil and other metabolites, allowing simultaneous quantitation of both drugs. The detection limit for both gallopamil and norgallopamil was 0.9 ng/ml. This method has been successfully used for the determination of gallopamil and norgallopamil following the administration of 25-, 37.5-, and 50-mg oral doses of drug.