Pharmacokinetics and dialysability of isradipine in chronic haemodialysis patients

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.

Management of hypertension in hemodialysis patients

The relationship of hypertension with adverse outcomes is uncertain in the hemodialysis population. If hypertension is an etiologically significant cardiovascular risk factor in hemodialysis patients, the first step would be to assess the level of BP accurately. BP obtained at home over a week and averaged using a validated oscillometric automatic device can prove valuable. To the extent BP lowering influences cardiovascular outcomes, home BP of 150/90 mm Hg would warrant therapy, since it correlates with target organ damage and hypertension diagnosed by ambulatory BP monitoring. To manage hypertension, limiting dietary sodium intake and individualizing dialysate sodium delivery would be first steps. The magnitude of reduction in BP with dietary sodium restriction and the whether dialysate sodium can be safely limited in those who are hypotension-prone is unclear. Antihypertensive drug therapies can effectively reduce BP and are needed by the vast majority of hemodialysis patients. Whether control of hypertension translates into better outcomes is not known, but collective evidence suggests that hypertension should be controlled in hemodialysis patients.

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.

Calcium-channel entry blocker therapy for hypertensive patients with concomitant renal impairment: a focus on isradipine

In the treatment of hypertension in renally impaired patients, normalization of blood pressure alone may not be sufficient to prevent significant morbidity to the kidneys. Treatment must reduce pressure in the renal vasculature, otherwise glomerular filtration rate and renal plasma flow will continue to deteriorate. Isradipine a dihydropyridine calcium-channel blocker, has been investigated as a suitable treatment in this setting. Isradipine maintains glomerular filtration rate, preserves or enhances renal plasma flow, decreases renal vascular resistance, maintains or reduces filtration fraction, and exerts a sustained natriuretic effect, all of which may enable isradipine to slow the rate of progression of renal deterioration. In addition, isradipine may decrease proteinuria and may decrease glomerular capillary pressure by dilating both the efferent and afferent arterioles. Unlike older calcium-channel blockers, isradipine exhibits minimal cardiodepressant activity and is not associated with any negative inotropic effects. It is metabolized in the liver and dosage adjustments may not be necessary when administered to patients with renal insufficiency. Isradipine has a favorable renal effect profile and also has several properties that meet the requirements of other patient populations where an extra measure of antihypertensive safety is required, such as diabetics, dialysis patients, and transplant recipients. Side effects with isradipine are usually mild and transient, occurring in a dose-dependent manner.

Antihypertensive therapy with isradipine in patients with special safety concerns

Treatment of hypertension in the complicated patient requires a specialized approach focusing on the treatment of the blood pressure and concurrent medical problems. Therapy must be chosen in consideration of the patient's age, multiple illnesses, declining organ function, and possible drug interactions. This requires that the antihypertensive agent chosen have a demonstrated safe profile. In clinical trials, monotherapy with the calcium channel blocker (CCB) isradipine (ISR) at a recommended therapeutic dosage has controlled blood pressure with an excellent level of safety. In these studies, ISR had no significant effect on heart rate, cardiac conduction, or cardiac contractility and no negative effect on renal function. In hypertensive patients with both normal and impaired renal function, ISR significantly increased renal plasma flow while decreasing renal vascular resistance without decreasing glomerular filtration rate and filtration fraction. ISR has long-term natriuretic effects that may provide additional benefits in antihypertensive therapy. Most adverse effects associated with ISR are mild, transient, and related to vasodilation. The most frequently reported adverse reactions are headache, dizziness, and edema. ISR does not affect glycemic control or lipid metabolism in either diabetic or nondiabetic patients. It has no reported adverse interaction with some of the most commonly used medications for elderly patients, including digoxin, nitroglycerin, oral hypoglycemics, and hydrochlorothiazide. ISR may be used as a first-line agent for the treatment of hypertension in complicated patients.