• Journal of Pharmaceutical Investigation
• /
• v.24 no.4
• /
• pp.289-295
• /
• 1994

Pharmacokinetic drug interaction between phenytoin and verapamil was investigated following i.v. administration of two drugs concomitantly to rabbits. Verapamil was coadministered with phenytoin (5 mg/kg) to rabbits at the doses of 0.5,1 and 2 mg/kg, respectively. Plasma concentration and AUC of phenytoin were increased significantly, but volume of distribution and total body clearance were decreased significantly (p<0.05) at doses of 1mg and 2mg/kg of verapamil, respectively. From the results of this experiment, it is desirable that dosage regimen of phenytoin should be adjusted and that therapeutic drug monitoring should be performed for reduction of side or toxic effect when phenytoin should be administered with verapamil in clinical practice.

• Journal of Pharmaceutical Investigation
• /
• v.34 no.1
• /
• pp.15-21
• /
• 2004

The pharmacokinetics of orally administered verapamil (10 mg/kg) was studied in six rabbits after 20 min pretreatment with quercetin ad coadministration of quercetin (2.0 mg/kg, 1 mg/g and 20 mg/kg, respectively). Pretreatment with quercetin significantly (p < 0.01, p < 0.05) increased the plasma concentration of verapamil. However, coadministration of quercetin showed no significantly effect on the pharmacokinetic parameters of verapamil. The elimination rate constant $(K_{el})$ of verapamil pretreated with quercetin (1 mg/kg and 20 mg/kg) was significantly (p < 0.05) reduced compared with control. The area under the plasma concentration-time curve (AUC) and the peak concentration $(C_{max})$ of verapamil pretreated with quercetin (2.0 mg/kg, 10 mg/kg and 20 mg/kg) were increased significantly (p < 0.01, p < 0.05) compared with control. Pretreatment with quercetin (2.0 mg/kg, 10 mg/kg and 20 mg/kg) significantly (p < 0.01, p < 0.05) increased the relative bioavailability of verapamil to 159 - 219%. These results suggest that quercetin alters disposition of verapamil by inhibition of P-glycoprotein efflux pump and its first-pass metabolism. The dosage of verapamil should be adjusted when it is administered chronically with quercetin in a clinical situation.

• Korean Journal of Clinical Pharmacy
• /
• v.14 no.1
• /
• pp.32-35
• /
• 2004

The purpose of this study was to investigate the pharmacokinetic changes of verapamil in rabbits with hepatic disorder induced by carbon tetrachloride. The plasma concentrations of verapamil were increased significantly (p<0.05, in slight group; P<0.01, in moderate and severe group) in all groups of hepatic disorder compared to the control group. Morover, the $C_{max}\;in\;slight\;(77.9\%$ increase), moderate ($110\%$ increase), and severe ($174\%$ increase) hepatic disorder groups were significantly (p<0.05, in slight; p<0.01, in moderate and severe) higher than that in control rabbits. These resulted in significantly (p<0.05, in slight; p<0.01, in moderate and severe) greater area under the plasma concentration-time curve (AUC) in moderate ($49.8\%$ increase), moderate ($95.0\%$ increase), and severe ($144\%$ increase) hepatic disorder groups than that in control rabbits. Hence, the relative bioavailability values were 149, 195, and $244\%$ for slight, moderate, and severe hepatic disorder groups, respectively. This could be due to decrease in metabolism of verapamil in the liver because of suppressed hepatic function in the hepatic disorder groups because verapamil is mainly metabolized in the liver.

• YAKHAK HOEJI
• /
• v.49 no.5
• /
• pp.380-385
• /
• 2005

The aim of this study is to investigate the effects of verapamil on the pharmacokinetics of tamoxifen following oral administration of tamoxifen with verapamil to rats. Tamoxifen (10 mg/kg) was administered orally in the presence or absence of verapamil (1, 3 or 6 mg/kg). Compared to the control group (given tamoxifen alone), the presence of verapamil significantly (p<0.05 by 1 mg/kg, p<0.01 by 3 and 6 mg/kg) increased the areas under the plasma concentration-time curve (AUC) and the peak concentrations ($C_{max}$) of tamoxifen. Consequently, the relative bioavailability ($RB\%$) of tamoxifen with verapamil was 1.6-2.1 fold higher than that of the control. But the time to reach peak concentration ($T_{max}$) and the terminal half-life ($t_{1/2}$) of tamoxifen were not altered significantly in the presence of verapamil. The increased AUC and $C_{max}$ of tamox­ifen in the presence of verapamil might be associated with the inhibition by verapamil of the P-glycoprotein and the first­pass metabolizing enzyme CYP3A4 in small intestinal mucosa. The drug interaction should be taken into consideration when tamoxifen is used to the patient with verapamil in the clinical setting.

• Korean Journal of Clinical Pharmacy
• /
• v.18 no.1
• /
• pp.6-10
• /
• 2008

This study investigated the effect of long-term administration of pioglitazone on the pharmacokinetics of verapamil in rats. Pharmacokinetic parameters of verapamil were determined after oral administration of verapamil (9 mg/kg) in rats coadministered pioglitazone (0.5 mg/kg) or pretreated with pioglitazone (0.5 mg/kg) for 3 and 9 days. Compared to oral control group, the presence of pioglitazone significantly (p<0.05) increased the area under the plasma concentration-time curve (AUC) of verapamil by 48.6% (coad), 61.1% (3 days) and 56.5% (9 days), and the peak concentration($C_{max}$) by 65.1% (coad), 76.8% (3 days) and 66.4% (9 days). The absolute bioavailability (AB%) of verapamil was significantly (p<0.05) higher by 6.2% (coad), 6.7% (3 days), 6.5% (9 days) compared to control (4.2%), and presence of pioglitazone was no significant change in the terminal half-life ($t_{1/2}$) and the time to reach the peak concentration($T_{max}$) of verapamil. Our results indicate that pioglitazone significantly enhanced oral bioavailability of verapamil in rats, implying that presence of pioglitazone could be effective to inhibit the CYP3A4-mediated metabolism of verapamil in the intestine. Drug interactions should be considered in the clinical setting when verapamil is coadministrated with pioglitazone.

• YAKHAK HOEJI
• /
• v.40 no.2
• /
• pp.135-140
• /
• 1996

Ion-selective poly(vinyl chloride)(PVC) membrane electrodes for the determination of the calcium antagonist verapamil and its pharmaceutical preparations were described. Verapam il-superchrome garnet Y(SGY), lumogallion(LG), acid red 97(AR97), Dragendorff(DD) and Meyer reagent ion pairs were inverstigated as an electroactive compound for membrane electrode. Stable potentiometric response was obtained with azo dye at pH 6.5-4.0 and with DD, and Meyer reagent at pH 6.5-3.0. The best plasticizer was 49w/w% 2-nitrophenyl octyl ether for azo dye, and 65.3w/w% tri(n-butyl) citrate for DD and Meyer reagent. Potentiometric response slopes of optimized membrane electrodes based on SGY, LG, AR97, DD, and Meyer complex for verapamil were 52.49, 54.88, 50.81, 54.13 and 49.31 mV/dec., respectively. Lower limits of linear range were $1.0{\times}10^6M$ for SGY, LG, and AR97, while those for DD and Meyer reagent were $4{\times}10^{-6}M$. Detection limits for all these electrodes were $1{\times}10^{-5}M,\;4{\times}10^{-6}M,\;1.8{\times}10^{-6}M,\;8{\times}10^{-7}M,\;and\;1{\times}10^{-6}M$ with relative standard deviation of 2.56, 3.6, 3.96, 2.56, 3.20%, respectively.

• Journal of Pharmaceutical Investigation
• /
• v.37 no.2
• /
• pp.107-111
• /
• 2007

Epigallocatechin gallate (EGCC), a flavonoid, is the main component of green tea extracts. EGCG has been reported to be an inhibitor of P-glycoprotein (P-gp) and cytochrom P450 3A(CYP3A4). This study investigated the effect of long-term administration of EGCG on the pharmacokinetics of verapamil in rats. Pharmacokinetic parameters of verapamil were determined after oral administration of verapamil (9 mg/kg) in rats pretreated with EGCG (7.5 mg/hg) for 3 and 9 days. Compared to oral control group, the presence of EGCG significantly (p<0.01) increased the area under the plasma concentration-time curve (AUC) of verapamil by 102% (coad), 83.2% (3 days) and 52.3% (9 days), and the peak concentration $(C_{max})$ by 134% (coad), 120% (3 days) and 66.1% (9 days). The absolute bioavailability (A.B.%) of verapamil was significantly (p<0.01) higher by 8.4% (coad), 7.7% (3 days), 6.4% (9 days) compared to control (4.2%), and presence of EGCG was no significant change in the terminal half-life $(t_{1/2})$ and the time to reach the peak concentration $(T_{max})$ of verapamil. Our results indicate that EGCG significantly enhanced oral bioavailability of verapamil in rats, implying that presence of EGCG could be effective to inhibit the CYP3A4-mediated metabolism and P-gp efflux of verapamil in the intestine. Drug interactions should be considered in the clinical setting when verapamil is coadministrated with EGCG or EGCG-containing dietary.

• Archives of Plastic Surgery
• /
• v.36 no.1
• /
• pp.11-18
• /
• 2009

Purpose: Excessive scarring in the forms of keloid and hypertrophic scar could be a consquence of the accumulation of granulation tissue cells due to aberrant control of apoptosis. Verapamil retard extracelluar matrix production and inhibits VEGF production in primary cultured keloid fibroblast. The object of this study was effect of verapamil on VEGF expression and apoptosis in early wound scarring of the rabbit ear. Methods: Full thickness wounds were created on the ventral side of 6 New Zealand rabbits's ear. 16 days after initial wounding verapamil and saline were injected each scars and scars were harvested 1 week, 2 weeks, 4 weeks later. The wounds were stained with hematoxylin and eosin, TUNEL stain, immunohistochemical stain for VEGF and calculated scar elevation index. Results: Histologic analaysis demonstrated significant reduction in inflammation, vascularity and improvement in dermal collagen organization in experimental group. In TUNEL staining apotosis positive cells were increased and immunohistochemial staining of VEGF demonstrated significant reduction of VEGF expression in experimental group. No significant difference was noted in scar elevation index between two groups. Conclusion: This study suggest that intralesional injection of verapamil on early wound scarring of the rabbit ear decreased VEGF production and increased apoptosis and have a benefit on the pathophysiology of scar formation.

• Journal of The Korean Society of Clinical Toxicology
• /
• v.16 no.1
• /
• pp.9-14
• /
• 2018

Purpose: Intravenous lipid emulsion (ILE) has been shown to have significant therapeutic effects on calcium channel blocker overdose in animal studies and clinical cases. In this preliminary experiment, we investigated the hemodynamic changes and survival in a rat model of verapamil intoxication. Methods: Fourteen male Sprague-Dawley rats were sedated and treated with ILE or normal saline (control), followed by continuous intravenous infusion of verapamil (20 mg/kg/h). Mean arterial pressure and heart rate of rats were monitored during the infusion. In addition, the total dose of infused verapamil and the duration of survival were measured. Results: Survival was prolonged in the ILE group ($32.43{\pm}5.8min$) relative to the control group ($24.14{\pm}4.3min$) (p=0.01). The cumulative mean lethal dose of verapamil was higher in the ILE group ($4.3{\pm}0.7mg/kg$) than in the control group ($3.2{\pm}0.5mg/kg$; p=0.017). Conclusion: ILE pretreatment prolonged survival and increased the lethal dose in a rat model of verapamil poisoning.

• Journal of Chest Surgery
• /
• v.41 no.5
• /
• pp.541-549
• /
• 2008

Background: Vasoconstrictor-induced reduction in arterial graft diameter can cause significant flow deprivation. The aim of this study was to evaluate the effect of vasodilator pretreatment on vasoconstrictor-induced blood vessel spasm in vitro. Material and Method: Rabbit brachial arteries (BA) and celiac arteries (CA) were cut into rings $(3{\sim}4mm)$ and suspended with a force displacement transducer (TSD $125C^{(R)}$, Biopac Inc. USA) in a tissue bath filled with 5 mL modified Krebs solution bubbled with 5% $CO_2$ and 95% $O_2\;at\;38^{\circ}C$. The rings were contracted with vasoconstrictors, and the developed tension changes were considered control values. The rings were then pre- treated with $30{\mu}M$ nitroglycerin, nicardipine, verapamil, and papaverine, respectively, for 40 minutes and rinsed with the physiologic buffered salt solution three times every 15 min. The vasoconstrictor-induced tension changes after the previous procedure were considered experimental values. Data are expressed as the percentage tension induced by vasoconstrictors before and after pretreatment with vasodilators. Result: Nicardipine depressed vasoconstriction induced by norepinephrine, angiotensin II (All), and U46619 in both the BA and the CA more significantly than did nitroglycerin (p<0.01) and verapamil (p<0.05). Verapamil depressed vasoconstriction induced by 5-hydroxytryptamine (5HT), All, and U46619 in the BA and by 5HT in the CA more significantly than did nitroglycerin (p<0.01). Conclusion: These findings suggest that both nicardipine and verapamil effectively depressed vasoconstrictor action. Nicardipine is thought to be more effective than verapamil for the prevention of vasoconstrictor action.