Haemodialysis does not affect the pharmacokinetics of nifedipine

Extracorporeal treatment for calcium channel blocker poisoning: systematic review and recommendations from the EXTRIP workgroup

BACKGROUND

Calcium channel blockers (CCBs) are commonly used to treat conditions such as arterial hypertension and supraventricular dysrhythmias. Poisoning from these drugs can lead to severe morbidity and mortality. We aimed to determine the utility of extracorporeal treatments (ECTRs) in the management of CCB poisoning.

METHODS

We conducted systematic reviews of the literature, screened studies, extracted data, summarized findings, and formulated recommendations following published EXTRIP methods.

RESULTS

A total of 83 publications (6 in vitro and 1 animal experiments, 55 case reports or case series, 19 pharmacokinetic studies, 1 cohort study and 1 systematic review) met inclusion criteria regarding the effect of ECTR. Toxicokinetic or pharmacokinetic data were available on 210 patients (including 32 for amlodipine, 20 for diltiazem, and 52 for verapamil). Regardless of the ECTR used, amlodipine, bepridil, diltiazem, felodipine, isradipine, mibefradil, nifedipine, nisoldipine, and verapamil were considered not dialyzable, with variable levels of evidence, while no dialyzability grading was possible for nicardipine and nitrendipine. Data were available for clinical analysis on 78 CCB poisoned patients (including 32 patients for amlodipine, 16 for diltiazem, and 23 for verapamil). Standard care (including high dose insulin euglycemic therapy) was not systematically administered. Clinical data did not suggest an improvement in outcomes with ECTR. Consequently, the EXTRIP workgroup recommends against using ECTR in addition to standard care for patients severely poisoned with either amlodipine, diltiazem or verapamil (strong recommendations, very low quality of the evidence (1D)). There were insufficient clinical data to draft recommendation for other CCBs, although the workgroup acknowledged the low dialyzability from, and lack of biological plausibility for, ECTR.

CONCLUSIONS

Both dialyzability and clinical data do not support a clinical benefit from ECTRs for CCB poisoning. The EXTRIP workgroup recommends against using extracorporeal methods to enhance the elimination of amlodipine, diltiazem, and verapamil in patients with severe poisoning.

Clearance of cardiovascular medications during hemodialysis

PURPOSE OF REVIEW

To review the current understanding of hemodialysis-mediated clearance of commonly used cardiovascular medications.

RECENT FINDINGS

Although cardiovascular drug dialyzability is poorly understood, many drug classes appear to include agents with substantially different degrees of dialyzability. Recent data suggest that more readily dialyzable beta-blockers associate with higher short-term mortality in patients initiating these drugs when on hemodialysis. Although this relationship was not observed in a later study with angiotensin-converting enzyme inhibitors of varying dialyzability, studies of this kind are currently limited by pharmacokinetic data that are either incomplete or no longer applicable to modern hemodialysis procedures.

SUMMARY

There are substantial deficits in our understanding of cardiovascular medication dialyzability, which relates in large part to advances in the process of hemodialysis that have rendered older studies of dialyzability irrelevant. The importance of cardiovascular disease in patients receiving hemodialysis demands a better understanding of the effect hemodialysis exerts on cardiovascular drug pharmacokinetics.

Pharmacokinetics and dialysability of naltrexone in patients undergoing hemodialysis

The disposition of naltrexone (NLT) (REVIA), an opioid antagonist intended for patients with impaired renal function and with severe intractable itching refractory to regular antipruritic therapy, was characterized. Hemodialysis effects on both efficacy and elimination of NLT also were assessed. We developed a simple, sensitive and selective reverse-phase high-performance liquid chromatographic (HPLC) method for measuring NLT plasma concentration in hemodialysis patients treated to relieve pruritus. NLT and the internal standard, naloxone (NLX) were extracted from plasma using a solid-phase extraction method with sep-pack C18 cartridge. The method was employed to determine both naltrexone pharmacokinetics and dialysability parameters during 4-h in dialyzed patients with chronic renal impairment. Thus, seven patients (2 men, 5 women) with end-stage renal disease and pruritus on regular hemodialysis were included. They received one tablet of NLT (Revia, 50 mg) orally prior dialysis session. The Cmax at the inlet and at the outlet the dialyzer were higher (255+/-117 ng/mL and 206+/-137 ng/ml respectively) in comparison with healthy subjects (9 - 44 ng/mL). The decrease hepatic first-pass metabolism of NLT consecutive to end-stage renal disease and the renal impairment could explain the increased levels of the drug in plasma. Tmax before and after dialysis plates remain unchanged as healthy subjects (approximately 1h). With regard to dialysability, a high dialyzer extraction ratio averating 30 % was found with a low dialysis clearance of 58.70+/-17 mL/min. The amount removed by dialysis is only 1.27 mg. We concluded that hemodialysis has little effect on NLT blood levels, and consequently on drug pharmacokinetics, when the drug is delivered to dialyzed patients following oral route. Thus, dosage adjustement is not required in the presence of advanced dialysis-dependant renal failure. In patients with end-stage renal disease, hemodialysis does not result in clinically significant alterations in the disposition of NLT. Post-dialysis supplementation is not required. These data suggest that there is no pharmacokinetic basis for modification of the initial dosage, but in view of NLT plasma concentration levels in the patients, a clinician could determine whether dosage adjustment are necessary and, if so, make the required calculations accurately.

Calcium-channel blockers and end-stage renal disease: pharmacokinetic and pharmacodynamic considerations

PURPOSE OF REVIEW

To characterize the pharmacokinetics and pharmacodynamics of the different calcium-channel blockers.

RECENT FINDINGS

Calcium-channel blockers have been in use for some time in the end-stage renal disease population. Their primary use has been as antihypertensive and antianginal therapies. In this regard, they are effective agents. Recently, it has been noted that dialysis-related hypotension occurs less frequently in calcium-channel blocker treated patients. Also, access patency and overall patient survival are improved with calcium-channel blocker therapy.

SUMMARY

Calcium-channel blockers are useful agents for the control of hypertension in end-stage renal disease patients and appear to favorably influence survival in this population. Calcium-channel blockers are not dialyzable and their pharmacokinetics do not substantially change with renal failure therefore they do not require dose adjustment based on level of renal function. Too few studies exist to determine if individual calcium-channel blockers differ in their effects. Prospective, randomized, controlled clinical trials are needed in the end-stage renal disease population to better understand the role of calcium-channel blockers in the excess cardiovascular disease burden of this population.

Human variability in CYP3A4 metabolism and CYP3A4-related uncertainty factors for risk assessment

CYP3A4 constitutes the major liver cytochrome P450 isoenzyme and is responsible for the oxidation of more than 50% of all known drugs. Human variability in kinetics for this pathway has been quantified using a database of 15 compounds metabolised extensively (>60%) by this CYP isoform in order to develop CYP3A4-related uncertainty factors for the risk assessment of environmental contaminants handled via this route. Data were analysed from published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and other subgroups using parameters relating primarily to chronic exposure [metabolic and total clearances, area under the plasma concentration-time curve (AUC)] and acute exposure (Cmax). Interindividual variability in kinetics was greater for the oral route (46%, 12 compounds) than for the intravenous route (32%, 14 compounds). The physiological and molecular basis for the difference between these two routes of exposure is discussed. In relation to the uncertainty factors used for risk assessment, the default kinetic factor of 3.16 would be adequate for adults, whereas a CYP3A4-related factor of 12 would be required to cover up to 99% of neonates, which have lower CYP3A4 activity.

Effect of dialysis on exogenous dopamine in haemodialysed critically ill patients

A sensitive and specific high performance liquid chromatographic method (HPLC) was developed for measuring dopamine (DA) in human plasma samples. Dihydroxybenzylamine (DHBA) was employed as an internal standard. Following solvent extraction and separation on a C18 ion-pairing reversed phase column, the drug was detected by a fluorescence detector with excitation and emission wavelengths of 233 nm and 345 nm, respectively. This method was employed to evaluate dopamine dialysability in seven haemodialysed patients under continuous infusion of a positive inotropic agent. Results showed a high dialyser extraction ratio averaging 38.3%, but a low dialysis clearance of 67 ml/min. The fraction removed by dialysis is 2.5%. We concluded that haemodialysis has little effect on dopamine blood levels, and consequently on drug pharmacokinetics, when the drug is delivered to haemodialysed patients under intravenous infusion.

Solid phase extraction and high performance liquid chromatographic determination of dobutamine in plasma of dialysed patients

An isocratic reversed-phase high performance liquid chromatographic method has been developed for th e determination of dobutamine in the plasma of dialysed patients. A solid phase extraction method with a Sep-Pak C18 cartridge was used to isolate the drug and isoxsuprine (internal standard) from plasma. The separation was carried out on an ODS-Hypersil column with 0.1 M phosphate buffer:acetonitrile:methanol (72:20:8 v/v/v) as the mobile phase. The recovery of dobutamine added to plasma by the extraction procedure was 87 +/- 2.3% (mean +/- SD). The accuracy and reproducibility of the method were within acceptable limits over the concentration range 0-1000 ng/mL. Quantification was by fluorescence detection at 275 nm excitation and 310 nm emission wavelengths with a detection limit of 5 ng/mL for dobutamine. This procedure was applied to ascertain the pharmacokinetics of dobutamine infusion in nine patients with cardiogenic shock and end-stage renal disease undergoing haemodialysis.

Clinical pharmacokinetics of calcium antagonists. An update

The calcium antagonists are valuable and widely used agents in the management of essential hypertension and angina. There is an increasing number of new agents to add to the 3 prototype substances nifedipine, diltiazem and verapamil. These new agents are dihydropyridines structurally related to nifedipine. However, they tend to have longer elimination half-lives (t 1/2 beta) and may be suitable for twice-daily administration. Amlodipine is an exception with a t 1/2 beta in excess of 30h. Apart from elimination rates, however, the pharmacokinetic characteristics of the newer agents have a notable tendency to resemble those of the established agents. They are highly cleared drugs, are relatively highly protein bound. As they are subject to significant first-pass metabolism, old age and hepatic impairment will increase their plasma concentrations due to a reduced first-pass effect. Renal impairment does little to their pharmacokinetics since the fraction eliminated unchanged by the kidney is small. For most agents, plasma concentration-response relationships have been described. Interesting areas for further research include chronopharmacokinetics, stereoselective pharmacokinetics and lipid solubility. Drugs affecting hepatic blood flow and drug metabolising capacity have predictable interaction potential. Some of the newer calcium antagonists will, like verapamil, increase plasma digoxin concentrations. Verapamil and diltiazem decrease phenazone (antipyrine) metabolism and therefore tend to decrease the metabolism of other drugs.

Inhibitory effect of uraemia on the hepatic clearance and metabolism of nicardipine

1. The principal aim of this study was to investigate the effect of renal impairment on the pharmacokinetics of nicardipine following intravenous and oral dosing. 2. The plasma clearance of nicardipine was significantly lower at 6.5 ml min-1 kg-1 in patients with impaired renal function, compared with a mean value of 10.4 in patients with normal renal function and with 12.5 ml min-1 kg-1 in patients on regular haemodialysis treatment. 3. In comparison to the patients with normal renal function, there were significant increases in AUC and Cmax in the patients with renal impairment. These increases were particularly marked during chronic dosing - AUC was increased by 163%, Cmax by 127% and apparent oral bioavailability by 90%. There were no such increases in the dialysis group whose values were similar to those for normal renal function. 4. There were no significant differences in volume of distribution or protein binding, nor in the measured indices of hepatic function to account for the reduction in drug clearance in the patients with renal impairment. 5. The results of this study indicate that renal impairment may have a significant and potentially important impact on the disposition of a drug which, under normal circumstances, is highly extracted by the liver. Accumulation of a metabolic 'inhibitor' substance is a possible explanation.

Pharmacokinetics of newer drugs in patients with renal impairment (Part II)

Cardiovascular diseases occur frequently in patients with renal failure. Any pharmacokinetic impairment in these diseases should be considered when individualizing drug therapy. The pharmacokinetics of new cardiovascular drugs in uraemic patients are reviewed: alpha- and beta-blocking agents, ACE inhibitors, centrally acting antihypertensive agents, calcium antagonists, antiarrhythmic agents and inotropic agents. Guidelines are proposed for adjustment of dosage regimens as a function of renal impairment. Renal or extrarenal elimination of drugs and their metabolites, and the activity of the latter, are taken into account. The disposition of new drugs such as flestolol, alacepril, delapril, propafenone, milrinone or enoximone, is not well documented in patients with renal failure. Further characterizations of the elimination of these compounds are needed and the potential therapeutic or toxic effects of the metabolites require evaluation to determine whether the dosage needs to be adjusted. Until such investigations are performed, those drugs should not be used in uraemic patients; if no therapeutic alternative is available, clinical controls are necessary at regular intervals. Relationships between pharmacological or therapeutic effects and drug plasma concentrations should be evaluated for such long term use drugs. The knowledge of a plasma concentration therapeutic window is important to provide information which will be useful in determining appropriate drug dosage in renal failure.

Tianeptine and its main metabolite. Disposition in chronic renal failure and haemodialysis

The disposition of the antidepressant tianeptine and its MC5 metabolite (pentanoic acid analogue of tianeptine) was studied following a single 12.5 mg oral dose of tianeptine sodium salt in 20 patients with chronic renal failure. In 12 patients (group I) having a creatinine clearance of less than 19 ml.min-1 the pharmacokinetics parameters for tianeptine and MC5 metabolite were determined and compared with those obtained in a matched control group (group II). The other 8 patients (group III) were functionally anephric and were studied during 1 dialysis to assess the haemodialysis clearances of tianeptine and MC5 metabolite. The comparison between groups I and II showed that renal failure did not appear to affect the disposition of parent tianeptine. However, the MC5 metabolite terminal half-life was found to be increased in renal patients compared to controls (14.2 +/- 9.3 h vs 4.9 +/- 1.7 h). Due to a large interindividual variability the difference did not reach a significant level (P = 0.054). According to the antidepressant activity of the MC5 metabolite in pharmacological tests, the sustained rise in its plasma level suggests that a reduced daily dose should be administered and 12.5 mg of tianeptine should be given twice daily to patients with chronic renal failure. In patients from group III elimination of the compounds by haemodialysis was found to be low. The dialysis clearances were 3.9 +/- 9.9 ml.min-1 and 19.2 +/- 8.6 ml.min-1 for tianeptine and its MC5 metabolite respectively. This low dialysability has 2 clinical implications. Firstly, patients currently undergoing haemodialysis and treated by tianeptine could be given the drug without taking dialysis into account. Secondly, haemodialysis does not appear to be an effective method for tianeptine elimination in cases of overdosage.

Nifedipine as an antihypertensive drug in patients with renal failure--pharmacokinetics and effects

Pharmacokinetics and pharmacodynamics of nifedipine were studied in 12 patients with renal failure and hypertension, after a single dose and during an 18-week treatment period. The plasma concentrations of nifedipine and its first pyridine metabolite were measured by gas chromatography mass spectrometry. The oral plasma clearance of nifedipine was 1189 +/- 876 ml min-1, and the mean plasma half-life (t1/2) was 5.99 +/- 3.05 h. The pyridine metabolite was not retained. Plasma concentrations of nifedipine were found to be significantly correlated with the effects on blood pressure, forearm blood flow and peripheral resistance, and these effects did not vary with the degree of renal failure. Normotension was achieved in eight of the nine patients observed over a period of 4 months with doses in the range 20-40 mg, administered twice daily. The mean Cr-EDTA clearance remained unchanged during the study (initial value 31.4 +/- 12.3 ml min-1; final value 32.7 +/- 14.4 ml min-1), and in three patients it increased. Nifedipine induces a slight increase in metabolic rate in patients with renal failure, but it is not necessary to modify the dose. It is effective in lowering blood pressure, has mild side-effects and may improve renal function in some patients.

Calcium channel antagonists: Part VI: Clinical pharmacokinetics of first and second-generation agents

A survey of the pharmacokinetic properties of the three prototypical calcium antagonist agents shows that they have in common a very high rate of hepatic first-pass metabolism with, in the case of verapamil and diltiazem, the formation of an active metabolite that affects the dose during chronic therapy. Therefore, the major factor altering the pharmacokinetic properties and the dose of the drug required is the capacity of the liver to metabolize the drug, which in turn depends on the hepatic blood flow and the activity of the hepatic metabolizing systems. Hence liver disease, a low cardiac output, and coadministration of certain drugs inducing or inhibiting the hepatic enzymes, all indirectly affect the pharmacokinetic properties of the calcium antagonists. There are also other potential drug interactions of a kinetic or dynamic nature that may arise. In general, renal disease has little effect on the pharmacokinetics of calcium antagonists.

Pharmacokinetics of nisoldipine in renal dysfunction

The pharmacokinetics of nisoldipine have been studied after oral administration of one 10 mg tablet to 3 groups of patients: Group A (n = 8) with a mean creatinine of 90 ml/min, Group B (n = 8) with a mean creatinine clearance of 12 ml/min and Group C of 12 patients on maintenance haemodialysis. All of them were studied off-dialysis and 7 were also studied on a dialysis day. No significant differences were observed between Groups A, B and C (on an interdialysis day) in AUC (0-7h), tmax, Cmax and plasma protein binding. Unchanged nisoldipine could not be recovered from the urine in any patient. Haemodialysis did not significantly affect AUC, tmax and Cmax, and nisoldipine could not be detected in the dialysate. The results indicate that the dose of nisoldipine need not be changed in patients with renal dysfunction, and that a supplementary dose is not required after haemodialysis. Blood pressure in the uraemics fell more than in the patients with good renal function.

Rectal administration of nifedipine: haemodynamic effects and pharmacokinetics in hypertensives

The haemodynamic effects and pharmacokinetics of nifedipine suppositories, used mainly for hypertensive emergencies, were studied in 10 severely hypertensive patients. Following rectal administration, significant hypotensive effects occurred after 0.5 h and lasted until 7 h after administration. The mean (+/- SE) maximum decreases in systolic and diastolic blood pressures 1.5 h after administration were: systolic, 61.8 +/- 7.9 mmHg (P less than 0.001); and diastolic, 30.8 +/- 4.0 mmHg (P less than 0.001). No serious side-effects were reported and heart rate did not change significantly. Mean nifedipine concentration in the blood peaked at 52.4 ng/ml, 1 h after administration and, after 7 h, was still 14.3 ng/ml which is higher than the minimum plasma concentration required for hypotensive effects to occur. There was a close correlation between nifedipine concentration in the blood and hypotensive effects. These results indicate that rectal administration of nifedipine should be regarded as a useful alternative treatment in hypertensive emergencies.

Clinical pharmacokinetics of verapamil, nifedipine and diltiazem

The calcium antagonists diltiazem, nifedipine and verapamil are widely used in the treatment of coronary heart disease, arterial hypertension, certain supraventricular tachyarrhythmias and obstructive hypertrophic cardiomyopathy. During recent years their pharmacokinetic properties and metabolism have been studied in more detail. Although these 3 calcium antagonists exhibit great diversity in chemical structure, they exhibit common pharmacokinetic properties. These drugs are extensively metabolised and only traces of unchanged drugs are eliminated in urine. Their systemic plasma clearances are high and dependent on liver blood flow. Therefore, their bioavailabilities (diltiazem 40 to 50%; nifedipine 40 to 50%; verapamil 10 to 30%) are low despite almost complete absorption following oral administration. During long term treatment, oral clearance decreases and bioavailability increases due to saturation of hepatic first-pass metabolism. Pronounced intra- and inter-individual variations in clearance and bioavailability are observed. In patients with liver cirrhosis the various pharmacokinetic parameters are grossly altered. Clearance decreases, elimination half-life is substantially prolonged, and bioavailability more than doubles. In addition, the volume of distribution increases. Whereas renal disease has no impact on the pharmacokinetics of diltiazem and verapamil, elimination half-life of nifedipine increases in relation to the degree of renal impairment due to an increase in volume of distribution. Systemic clearance, however, remains unchanged. The data so far available indicate that the plasma concentrations of these drugs correlate with both their electrophysiological and haemodynamic effects. However, no effective therapeutic plasma concentration range has been firmly established. As reliable clinical end-points are available for dose titration of calcium antagonists, it is doubtful whether therapeutic drug monitoring will be of great value. Calcium antagonists are often administered in combination with a variety of other drugs. Thus, the potential for both pharmacodynamic and pharmacokinetic drug interaction exists. The interaction between digoxin and these drugs is of clinical importance. Verapamil and diltiazem cause a significant increase in plasma digoxin concentrations. In contrast, nifedipine does not lead to a significant increase in the plasma digoxin concentration. The mechanism responsible for this interaction is inhibition of both renal and non-renal digoxin clearance.(ABSTRACT TRUNCATED AT 400 WORDS)