Hypertension sodium-channel inhibitor

These agents inhibit the Na-i- ion channei in the iuminai epitheiium. This causes hyperpolarisation of the iuminai membrane and iimits the transfer of cations across the iuminai surface. Flyperpolarisation not only prevents the reabsorption of Na-i- but aiso reduces the excretion of intracellular cations such as K+, Ca2+, Fi+ and Mg2+. The abiiity of sodium ion channel inhibitors to reduce the excretion of K+ is used to conserve body K+ in patients who are taking thiazide or loop diuretics and for this reason they are more commoniy known as the K-i-sparing diuretics. They are rarely used alone because their diuretic action is weak, instead they are administered in combination with thiazide or ioop diuretics for their antikaiuretic effect. Combination therapy is also synergistic when used in the treatment of hypertension. 

Essential hypertension is a symptom of modem society, and its treatment accounts for a sizeable portion of global prescriptions. As a result, there is a great interest in reported ethnic and racial differences reported in the literature. The use of appropriate therapy in Black patients has been best studied. As monotherapy, calcium channel blockers and diuretics appear to be most effective in Blacks, whereas P-blockers and ACE inhibitors produce smaller reductions in blood pressure (Kiowiski et al, 1985 Freis, 1986 Hall, 1990). However, this may more reflect the lower plasma renin, salt and water retention and intercellular sodium and calcium in Blacks, compared to other groups (Kiowiski et al., 1988). There are individual exceptions amongst patients and among drugs, even within these classes for example labetalol, a combined a-blockers and P-blockers, can be equally effective in both African-Americans and Caucasians and, as mentioned previously, the Chinese appear twice as sensitive to propranolol as Caucasians (Oster etal., 1987 Zhou etal., 1990). 

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