QT time prolongation
Adverse drug events
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Explanations of the substances for patients
We have no additional warnings for the combination of quinidine and abarelix. Please also consult the relevant specialist information.
The reported changes in exposure correspond to the changes in the plasma concentration-time curve [ AUC ]. We do not expect any change in exposure for quinidine, when combined with abarelix (100%). We do not expect any change in exposure for abarelix, when combined with quinidine (100%).
The pharmacokinetic parameters of the average population are used as the starting point for calculating the individual changes in exposure due to the interactions.
Quinidine has a mean oral bioavailability [ F ] of 72%, which is why the maximum plasma levels [Cmax] tend to change with an interaction. The terminal half-life [ t12 ] is 6.4 hours and constant plasma levels [ Css ] are reached after approximately 25.6 hours. The therapeutic window is narrow and the safety margin is therefore small. Even small changes in exposure can increase the risk of toxicity. The protein binding [ Pb ] is moderately strong at 84% and the volume of distribution [ Vd ] is very large at 139 liters, Since the substance has a low hepatic extraction rate of 0.23, displacement from protein binding [Pb] in the context of an interaction can lead to increased exposure. The metabolism mainly takes place via CYP3A4 and the active transport takes place partly via OATP1A2 and PGP.
The bioavailability of abarelix is unknown. The terminal half-life [ t12 ] is rather long at 316.8 hours and constant plasma levels [ Css ] are only reached after more than 1267.2 hours. The protein binding [ Pb ] is 97.5% strong. The metabolism via cytochromes is currently still being worked on.
|Serotonergic Effects a||0||Ø||Ø|
Rating: According to our knowledge, neither quinidine nor abarelix increase serotonergic activity.
|Kiesel & Durán b||2||++||Ø|
Recommendation: As a precaution, attention should be paid to anticholinergic symptoms, especially after increasing the dose and at doses in the upper therapeutic range.
Rating: Quinidine modulates the anticholinergic system to a moderate extent. The risk of anticholinergic syndrome with this medication is rather low if the dosage is in the usual range. According to our knowledge, abarelix does not increase anticholinergic activity.
QT time prolongation
Rating: In combination, quinidine and abarelix can potentially trigger ventricular arrhythmias of the torsades de pointes type.
General adverse effects
|Side effects||∑ frequency||qui||aba|
|Ventricular arrhythmia||0.0 %||0.01||n.a.|
Based on your answers and scientific information, we assess the individual risk of undesirable side effects. These recommendations are intended to advise professionals and are not a substitute for consultation with a doctor. In the restricted test version (alpha), the risk of all substances has not yet been conclusively assessed.
Abstract: QRS duration, QT interval, total electromechanical systole (QS(2)), left ventricular ejection time (LVET), and preejection period (PEP) were determined in five male and two female healthy volunteers in a fasting state at hourly intervals for 7 hours during a control period and after administration of 400 mg quinidine sulfate. Changes of QRS duration (delta QRS) and rate-corrected QT interval (delta QTc) were calculated before and after quinidine. Deviations of measured QS(2), LVET, and PEP from the normal were calculated as the differences between the observed interval and those predicted from the normal regression equation. The effect of quinidine on systolic time intervals (delta QS(2), delta LVET, DELTA PEP) were expressed as the differences between the deviations from the normal regression equation during the control period and after the drug administration. After quinidine sulfate delta QRS, delta LVET, delta PEP, and delta PEP, delta LVET were slight and inconsistent. However, delta QTc and delta QS(2) were significant (at P is less than 0.05 or better) from the first hour to the 7th hour and from the 2nd hour to the 5th hour, respectively. The mean maximum delta QTc was 44.8 milliseconds and delta QS(2) was 29.9 milliseconds. The significant changes of QTc and QS(2) seemed to occur at the plasma level range of 0.75-1.9 mug/ml. This study indicates that of the various systolic time interval measurements obtained after quinidine administration, the changes of QT interval and QS(2) are most significant and that these changes seem to occur even at low plasma levels.
Abstract: The absolute bioavailability of quinidine was studied in 11 hospitalized patients. A 400-mg dose of quinidine gluconate was administered to each patient by intravenous infusion and as an oral solution. Drug treatments were separated by a 72-hr period. In 8 patients, peak plasma quinidine concentrations were reached in 65 min after the oral dose; in the remaining 3 subjects, peak concentrations were reached later. From the ratio of the total area under the plasma concentration-time curves (AUCoral/AUCir), the absolute bioavailability of quinidine ranged from 44% to 89% (mean, 72). In 8 patients, the ratio of the total amount of quinidine excreted in the urine in 48 hr (AUinfinity oral/AUinfinity ir) indicated that the extent of quinidine bioavailability varied form 47% to 96% (mean, 73). The predicted bioavailability of quindine due to first-pass effects was 76+/-11%. It is concluded that absorption after the oral solution was rapid and that the reduction of quinidine bioavailability was due to first-pass hepatic drug removal.
Abstract: No Abstract available
Abstract: The elimination of quinidine is accomplished by a combination of renal excretion of the intact drug (15 to 40% of total clearance) and hepatic biotransformation to a variety of metabolites (60 to 85% of total clearance). Many of the metabolites appear to be pharmacologically active. Typical ranges for kinetic properites of quinidine in healthy persons are: apparent volume of distribution 2.0 to 3.5 litres/kg; elimination half-life 5 to 12 hours; clearance, 2.5 to 5.0 ml/min/kg. Quinidine clearance is reduced in the elderly, in patients with cirrhosis, and in those with congestive heart failure. Oral quinidine is available either as relatively rapidly absorbed conventional tablets (usually quinidine sulphate) or as a variety of slowly absorbed sustained release preparations. Absolute systemic availability generally is 70% or greater. Quinidine is 70 to 95% bound to plasma protein, primarily to albumin but also to a number of other plasma constituents. Binding is reduced in patients with cirrhosis, partly because of hypoalbuminaemia, but is not influenced by renal insufficiency. Clinical interpretation of total serum or plasma quinidine concentrations must be altered in patients with reduced or increased binding, since it is the unbound fraction which is pharmacologically active.
Abstract: No Abstract available
Abstract: We studied the interaction of disopyramide, quinidine, and procainamide with cardiac muscarinic receptors. In electrophysiological experiments, the effects of disopyramide, quinidine, procainamide, and atropine were determined on spontaneously depolarizing guinea pig right atria (GPRA) both in the presence and absence of pharmacologically induced (physostigmine) cholinergic stimulation. All four agents demonstrated a concentration-dependent antagonism of the negative chronotropic effects of physostigmine. The order of anticholinergic potency was atropine greater than disopyramide greater than quinidine greater than procainamide. The ability of disopyramide to antagonize the physostigmine induced slowing was stereoselective, (+)disopyramide greater than (-)disopyramide. In contrast, the ability of quinidine to antagonize the negative chronotropic effects of physostigmine was non-stereoselective, quinidine = quinine. In parallel experiments, we studied the ability of disopyramide, quinidine, procainamide, and atropine to compete with the radiolabeled muscarinic receptor antagonist [3H] quinuclidinyl benzilate ([3H]QNB) for binding to muscarinic receptors in crude homogenates of GPRA and membrane vesicles from canine ventricular myocardium. All four agents inhibited [3H]QNB binding to muscarinic receptors. The order of anticholinergic potency determined by the receptor binding studies was identical to that determined by the physiological studies. The interaction of disopyramide with muscarinic receptors was stereoselective, (+)disopyramide > (-)disopyramide. Quinidine was only slightly more potent than quinine in inhibiting [3H]QNB binding to muscarinic receptors. Interaction of antiarrhythmic drugs with muscarinic receptors satisfied criteria for a competitive interaction. The data from this study localize the anticholinergic effects of disopyramide and quinidine to the muscarinic receptor.
Abstract: Conflicting findings suggest that serum quinidine concentrations may be decreased or increased by nifedipine. We performed a double-blind, placebo-controlled trial of Latin-square design. Twelve healthy men received 3 days of pretreatment with nifedipine prolonged action (20 mg twice a day) or felodipine extended release (10 mg every day), another dihydropyridine calcium antagonist, followed by coadministration of quinidine (400 mg). Quinidine pharmacokinetics were not changed by either dihydropyridine. However, 3-hydroxyquinidine area under the concentration-time curve (AUC) and 3-hydroxyquinidine/quinidine AUC ratio were decreased by felodipine, consistent with reduced metabolite formation. Heart rates and adverse events were higher with felodipine, demonstrating lack of bioequivalence with nifedipine. The QTc interval did not deviate from that expected for the observed quinidine concentration, suggesting the pharmacokinetics of active quinidine metabolites were not markedly altered among treatments. Quinidine disposition did not appear to be changed sufficiently to be clinically important by sustained-release nifedipine and felodipine.
Abstract: OBJECTIVES: To examine the pharmacokinetic and pharmacodynamic interactions between quinidine and diltiazem because both drugs can inhibit drug metabolism. METHODS: Twelve fasting, healthy male volunteers (age, 24 +/- 5 years; weight, 75 +/- 10 kg) received a single oral dose of diltiazem (60 mg) or quinidine (200 mg), alone and on a background of the other drug, in a crossover study. Background treatment consisted of 100 mg quinidine twice a day or 90 mg sustained-release diltiazem twice a day for 2 day before the study day. RESULTS: Pretreatment with diltiazem significantly (p < 0.05) increased the area under the curve of quinidine from 7414 +/- 1965 to 11,213 +/- 2610 ng.hr/ml and increased its terminal elimination half-life (t1/2) from 6.8 +/- 1.1 to 9.3 +/- 1.5 hours. Its oral clearance was decreased from 0.39 +/- 0.1 to 0.25 +/- 0.1 L/hr/kg, whereas the maximal concentration was not significantly affected. Diltiazem disposition was not significantly affected by pretreatment with quinidine. Diltiazem pretreatment increased QTc and PR intervals and decreased heart rate and diastolic blood pressure. No significant pharmacodynamic differences were shown for diltiazem alone versus quinidine pretreatment. CONCLUSION: Diltiazem significantly decreased the clearance and increased the t1/2 of quinidine, but quinidine did not alter the kinetics of diltiazem with the dose used. No significant pharmacodynamic interaction was shown for the combination that would not be predicted from individual drug administration.
Abstract: BACKGROUND: Quinidine is eliminated mainly by CYP3A4-mediated metabolism. Itraconazole interacts with some but not all of the substrates of CYP3A4; it is therefore important to study the possible interaction of itraconazole with quinidine. METHODS: A double-blind, randomized, two-phase crossover study design was used with nine healthy volunteers. Itraconazole (200 mg) or placebo was ingested once a day for 4 days. A single 100 mg oral dose of quinidine sulfate was ingested on day 4. Plasma concentrations of quinidine, itraconazole, and hydroxyitraconazole, as well as cumulative excretion of quinidine into urine, were determined up to 24 hours. The ECG, heart rate, and blood pressure were also recorded up to 24 hours. RESULTS: On average the peak plasma concentration of quinidine increased to 1.6-fold (p < 0.05), and the area under the concentration-time curve of quinidine increased to 2.4-fold (p < 0.01) by itraconazole. The elimination half-life of quinidine was prolonged 1.6-fold (p < 0.001), and the area under the 3-hydroxyquinidine/quinidine ratio-time curve decreased to one-fifth (p < 0.001) by itraconazole. The renal clearance of quinidine decreased 50% (p < 0.001) by itraconazole, whereas the creatinine clearance was unaffected. The QTc interval correlated with the concentrations of quinidine during both itraconazole and placebo phases (r2 = 0.71 and r2 = 0.79, respectively; p < 0.01), although only minor changes between the phases were observed in other pharmacodynamic variables. CONCLUSIONS: Itraconazole increases plasma concentrations of oral quinidine, probably by inhibiting the CYP3A4 isozyme during the first-pass and elimination phases of quinidine. The decreased renal clearance of quinidine might be the result of the inhibition of P-glycoprotein-mediated tubular secretion of quinidine by itraconazole. The concentrations of quinidine should be closely monitored if itraconazole or some other potent CYP3A inhibitors are used with quinidine.
Abstract: The aim of this study was to evaluate the (3S)-3-hydroxylation and the N-oxidation of quinidine as biomarkers for cytochrome P-450 (CYP)3A4 activity in human liver microsome preparations. An HPLC method was developed to assay the metabolites (3S)-3-hydroxyquinidine (3-OH-Q) and quinidine N-oxide (Q-N-OX) formed during incubation with microsomes from human liver and from Saccharomyces cerevisiae strains expressing 10 human CYPs. 3-OH-Q formation complied with Michaelis-Menten kinetics (mean values of Vmax and Km: 74.4 nmol/mg/h and 74.2 microM, respectively). Q-N-OX formation followed two-site kinetics with mean values of Vmax, Km and Vmax/Km for the low affinity isozyme of 15.9 nmol/mg/h, 76.1 microM and 0.03 ml/mg/h, respectively. 3-OH-Q and Q-N-OX formations were potently inhibited by ketoconazole, itraconazole, and triacetyloleandomycin. Isozyme specific inhibitors of CYP1A2, -2C9, -2C19, -2D6, and -2E1 did not inhibit 3-OH-Q or Q-N-OX formation, with Ki values comparable with previously reported values. Statistically significant correlations were observed between CYP3A4 content and formations of 3-OH-Q and Q-N-OX in 12 human liver microsome preparations. Studies with yeast-expressed isozymes revealed that only CYP3A4 actively catalyzed the (3S)-3-hydroxylation. CYP3A4 was the most active enzyme in Q-N-OX formation, but CYP2C9 and 2E1 also catalyzed minor proportions of the N-oxidation. In conclusion, our studies demonstrate that only CYP3A4 is actively involved in the formation of 3-OH-Q. Hence, the (3S)-3-hydroxylation of quinidine is a specific probe for CYP3A4 activity in human liver microsome preparations, whereas the N-oxidation of quinidine is a somewhat less specific marker reaction for CYP3A4 activity, because the presence of a low affinity enzyme is demonstrated by different approaches.
Abstract: OBJECTIVE: To investigate the possible involvement of cytochromes CYP1A2 and CYP2C19 in the in vivo oxidative metabolism of quinidine. METHODS: This was an open study of six healthy young male volunteers. The pharmacokinetics of a 200-mg single oral dose of quinidine were studied before and during daily treatment with 100 mg fluvoxamine. Biomarkers of other isozyme activities in the form of caffeine, sparteine, mephenytoin, tolbutamide and cortisol metabolism were applied. RESULTS: The results showed a statistically significant median reduction of 2944% in the quinidine total apparent oral clearance, partial clearances by 3-hydroxylation and N-oxidation and residual clearance during fluvoxamine treatment. Renal clearance was unaffected by fluvoxamine. CONCLUSIONS: The effect of fluvoxamine on the formation clearances of 3-hydroxyquinidine and quinidine-N-oxide most likely reflects inhibition of cytochrome P4503A4 by fluvoxamine at clinically relevant doses. The results of this study do not rule out a possible involvement of CYP1A2 and CYP2C19 in the in vivo oxidative metabolism of quinidine.
Abstract: AIMS: In vitro studies suggest that the oxidation of quinidine to 3-hydroxyquinidine is a specific marker reaction for CYP3A4 activity. To assess the possible use of this reaction as an in vivo marker of CYP3A4 activity, we studied the involvement of cytochromes CYP2C9, CYP2E1 and CYP3A4 in the in vivo oxidative metabolism of quinidine. METHODS: An open study of 30 healthy young male volunteers was performed. The pharmacokinetics of a 200 mg single oral dose of quinidine was studied before and during daily administration of 100 mg diclofenac, a CYP2C9 substrate (n=6); 200 mg disulfiram, an inhibitor of CYP2E1 (n=6); 100 mg itraconazole, an inhibitor of CYP3A4 (n=6); 250 ml single strength grapefruit juice twice daily, an inhibitor of CYP3A4 (n=6); 250 mg of erythromycin 4 times daily, an inhibitor of CYP3A4 (n=6). Probes of other enzyme activities, caffeine (CYP1A2), sparteine (CYP2D6), mephenytoin (CYP2C19), tolbutamide (CYP2C9) and cortisol (CYP3A4) were also studied. RESULTS: Concomitant administration of diclofenac reduced the partial clearance of quinidine by N-oxidation by 27%, while no effect was found for other pharmacokinetic parameters of quinidine. Concomitant administration of disulfiram did not alter any of the pharmacokinetic parameters of quinidine. Concomitant administration of itraconazole reduced quinidine total clearance, partial clearance by 3-hydroxylation and partial clearance by N-oxidation by 61, 84 and 73%, respectively. The renal clearance was reduced by 60% and the elimination half-life increased by 35%. Concomitant administration of grapefruit juice reduced the total clearance of quinidine and its partial clearance by 3-hydroxylation and N-oxidation by 15, 19 and 27%, respectively. The elimination half-life of quinidine was increased by 19%. The caffeine metabolic index was reduced by 25%. Concomitant administration of erythromycin reduced the total clearance of quinidine and its partial clearance by 3-hydroxylation and N-oxidation by 34, 50 and 33%, respectively. Cmax was increased by 39%. CONCLUSIONS: The results confirm an important role for CYP3A4 in the oxidation of quinidine in vivo, and this applies particularly to the formation of 3-hydroxyquinidine. While a minor contribution of CYP2C9 to the N-oxidation of quinidine is possible, a major involvement of the CYP2C9 or CYP2E1 enzymes in the oxidation of quinidine in vivo is unlikely.
Abstract: We investigated the effect of cytochrome P450 induction by rifampicin on the in vivo oxidative metabolism of quinidine. The pharmacokinetics of a 200 mg oral single dose quinidine were studied before and after one week of daily treatment with 600 mg rifampicin in six healthy young male volunteers. Biomarker reactions of cytochrome P450 isozyme activities in the form of caffeine, sparteine, mephenytoin, tolbutamide and cortisol metabolism were applied. The median total apparent oral clearance and partial clearance by 3-hydroxylation of quinidine increased 9 times. The partial clearance by N-oxidation increased 6 times. The Cmax and the elimination half life were reduced 3 times. No statistically significant changes were found for quinidine tmax and renal clearance. The cortisol metabolic ratio increased 5 times, while no statistically significant effects were seen for other CYP marker reactions. The results indicate that the inductive effect of rifampicin is likely to be of clinical relevance particularly when used concomitantly with drugs metabolized by CYP3A4.
Abstract: Permeability glycoprotein (P-gp) mediates the export of drugs from cells located in the small intestine, blood-brain barrier, hepatocytes, and kidney proximal tubule, serving a protective function for the body against foreign substances. Intestinal absorption, biliary excretion, and urinary excretion of P-gp substrates can therefore be altered by either the inhibition or induction of P-gp. A wide spectrum of drugs, such as anticancer agents and steroids, are known P-gp substrates and/or inhibitors, and many cardiovascular drugs have recently been observed to have clinically relevant interactions as well. We review the interactions among commonly prescribed cardiovascular drugs that are P-gp substrates and observe interactions involving P-gp that may be relevant to clinical practice. Cardiovascular drugs with narrow therapeutic indexes (e.g., antiarrhythmic agents, anticoagulant agents) have demonstrated large increases in concentrations when coadministered with potent P-gp inhibitors, thus increasing the risk for drug toxicity. Therefore, dose adjustment or use of alternative agents should be considered when strong P-gp-mediated drug-drug interactions are present. Finally, interactions between novel drugs and known P-gp inhibitors are now being systematically evaluated during drug development, and recommended guidelines for the administration of P-gp substrate drugs will be expanded.