Calcium channel blockers types

Patients having high plasma renin activity (PRA) (>8 ng/(mLh)) respond best to an ACE inhibitor or a -adrenoceptor blocker those having low PRA (<1 ng/(mLh)) usually elderly and black, respond best to a calcium channel blocker or a diuretic (184). -Adrenoceptor blockers should not be used in patients who have diabetes, asthma, bradycardia, or peripheral vascular diseases. The thiazide-type diuretics (qv) should be used with caution in patients having diabetes. Likewise, -adrenoceptor blockers should not be combined with verapamil or diltiazem because these dmgs slow the atrioventricular nodal conduction in the heart. Calcium channel blockers are preferred in patients having coronary insufficiency diseases because of the cardioprotective effects of these dmgs. 

Although there is no evidence that the neuronal degeneration of AzD results, as in cardiovascular ischaemia, from the excitotoxicity of increased intracellular Ca +, some calcium channel blockers have been tried in AzD. They have had little effect but surprisingly a pyrrolidone derivative nefiracetam, which opens L-type voltage-sensitive calcium channels (VSCCs) reduces both scopolamine- and )S-amyloid-induced impairments of learning and memory in rats (Yamada et al. 1999). This effect can be overcome by VSCC antagonists, but nefiracetam has not been tried in humans. 

The benzhydryl substituent is common to many reported N-type calcium channel blockers. A recently reported series derived from the neuroepileptic flunarizine (5), which exhibits N-type calcium channel potency in a whole-cell patch-clamp assay (IC50 0.08 iM) as well as L-type potency... 

Ziconotide (45 Prialt ) Ziconotide (45) Peptide NP Animal Pain Acts as a selective /V-type voltage-gated calcium channel blocker 417 28... 

Another type of antihypertensive agent is a calcium channel blocker. This was discussed under amlodipine (no. 6) in Section 3.6. Finally, angiotension-converting enzyme (ACE) inhibitors are used in severe... 

Drugs that may be affected by indinavir include antiarrhythmics, clarithromycin, dihydropyridine calcium channel blockers, HMG-CoA reductase inhibitors, immunosuppressant agents, phosphodiesterase type 5 inhibitors, pimozide, saquinavir, trazodone, cisapride, amiodarone, benzodiazepines, ergot alkaloids, fentanyl, rifamycins, ritonavir. 

This arrhythmia usually occurs in young people and preponderantly in men. The electrocardiogram often shows right bundle branch block with left axis deviation (superior axis deviation). This type of VT is often sensitive to verapamil or other calcium channel blockers, but not to /3-blockers. Radiofrequency catheter ablation may be helpful to abolish it. 

L A. Verapamil is an L-type calcium channel blocker. Nitroglycerin and isosorbide are both organic nitrates and have no direct effect on L-type calcium channels at the SA node, while propranolol and metoprolol are (3-adrenoceptor blockers and will slow heart rate by blocking the actions of norepinephrine and epinephrine on (3-receptors at the SA node. 

TABLE 6 4. Differential effects of dihydropyridine L-type calcium channel blockers versus verapamil... 

FKiURE 6 5C. Efficacy of dihydropyridine L-type calcium channel blockers. Mean deviation from euthymia ratings (number of days in parentheses) in a patient with bipolar 11 disorder with ultra-ultrarapid cycling showing the following efficacy of nimodipine monotherapy efficacy of nimodipine-carbamazepine combination therapy unsuccessful transition from nimodipine to verapamil successful reinstitution of nimodipine-carbamazepine combination therapy and, finally, successful transition to isradipine-carbamazepine combination therapy. P <. 05 "nimodipine slowly tapered to zero. 

SULAR is an extended release tablet and should be swallowed whole. Tablets should not be chewed, divided, or crushed. SULAR should not be administered with a high-fat meal. Grapefruit juice, which has been shown to increase significantly the bioavailability of nisoldipine and other dihydropyridine type calcium channel blockers, should not be taken with SULAR... 

Other types of calcium channels are less sensitive to blockade by these calcium channel blockers (Table 12-4). Therefore, tissues in which these other channel types play a major role—neurons and most secretory glands—are much less affected by these drugs than are cardiac and smooth muscle. 

Most types of smooth muscle are dependent on transmembrane calcium influx for normal resting tone and contractile responses. These cells are relaxed by the calcium channel blockers (Figure 12-3). Vascular smooth muscle appears to be the most sensitive, but similar relaxation can be shown for bronchiolar, gastrointestinal, and uterine smooth muscle. In the vascular system, arterioles appear to be more sensitive than veins orthostatic hypotension is not a common adverse effect. Blood pressure is reduced with all calcium channel blockers. Women may be more sensitive than men to the hypotensive action of diltiazem. The reduction in peripheral vascular resistance is one mechanism by which these agents may benefit the patient with angina of effort. Reduction of coronary artery tone has been demonstrated in patients with variant angina. 

Calcium channel blockers minimally interfere with stimulus-secretion coupling in glands and nerve endings because of differences between calcium channel type and sensitivity in different tissues. Verapamil has been shown to inhibit insulin release in humans, but the dosages required are greater than those used in management of angina. 

The amount of trigger calcium that enters the cell depends on the availability of membrane calcium channels (primarily the L type) and the duration of their opening. As described in Chapters 6 and 9, sympathomimetics cause an increase in calcium influx through an action on these channels. Conversely, the calcium channel blockers (see Chapter 12) reduce this influx and depress contractility. 

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