لخّصلي

2.3.By blocking this rise, the calcium channel blockers produce arteriolar relaxation and decrease in vascular resistance.Sustained release formulations have their bioavailability and hypotensive effects significantly increased by food ingestion ( 15) but modifiedrelease and controlledrelease formulations do notseem tobe pharmacodynamically altered by meals (16, 17 ).The systemic hypertension produced by this vasoconstriction can be reduced by inhibiting the conversion of the relatively inactive angiotensin I to the potent angiotensin II by ACE.Although the effect is normally mild in persons with normal renal function, care should be used in those with decreased renal function and in those who are taking medications that ha ve potassium-retaining properties such as the K+-sparing diuretics or those on K+ supplementation.The effect of food ingestion and bioavailability of nifedipine has been well studied and the mode of delivery of nifedipine correlated with meals may significantly alter the clinical effects.Nifedipine and other dihydropyridines have increased oral bioavailability when ingested with grapefruit juice evidenced by hypotension and tachycardia ( 18,19 ).Newer classes of drugs related to the ACE inhibitors are the angiotensin II receptor antagonists such as losartan and valsartan.ACE inhibitors ha ve also been implicated in the loss ofboth protein and glucose in the urine.ACE Inhibitors Angiotensin II is one ofthe most potent vasoconstrictors used by the body.Calcium Channel Blockers Calcium channel blockers inhibit the elevation of calcium in the vascular smooth muscle required for contraction.A common side effect is hyperkalemia.2.4.

2.3. ACE Inhibitors Angiotensin II is one ofthe most potent vasoconstrictors used by the body. The systemic hypertension produced by this vasoconstriction can be reduced by inhibiting the conversion of the relatively inactive angiotensin I to the potent angiotensin II by ACE. ACE inihibitors can have adverse effects on the electrolyte balance ofpatients using them. A common side effect is hyperkalemia. Although the effect is normally mild in persons with normal renal function, care should be used in those with decreased renal function and in those who are taking medications that ha ve potassium-retaining properties such as the K+-sparing diuretics or those on K+ supplementation. Again, dietary intake may need to be adjusted for those patients prescribed this class of antihypertensive medication. ACE inhibitors ha ve also been implicated in the loss ofboth protein and glucose in the urine. The long-term effect of these losses is not well characterized. Dysgeusia or alteration of taste has also been noted to occur in patients using ACE inhibitors. This is most commonly seen with captopril. Dysgeusia may adversely affect food intake and should be watched for in these patients. Newer classes of drugs related to the ACE inhibitors are the angiotensin II receptor antagonists such as losartan and valsartan. These are purported to ha ve similar therapeutic effects as the ACE inhibitors, but with diminished side effects. Their bearing on nutritional status should be considered as similar to ACE inhibitors with similar precautions until better defined by further study. 2.4. Calcium Channel Blockers Calcium channel blockers inhibit the elevation of calcium in the vascular smooth muscle required for contraction. By blocking this rise, the calcium channel blockers produce arteriolar relaxation and decrease in vascular resistance. As a group, the calcium channel blockers are known to cause nausea and constipation. Minor elevations of liver function tests have been reported. These elevations may indicate interactions affecting presystemic metabolism. The effect of food ingestion and bioavailability of nifedipine has been well studied and the mode of delivery of nifedipine correlated with meals may significantly alter the clinical effects. Sustained release formulations have their bioavailability and hypotensive effects significantly increased by food ingestion ( 15) but modifiedrelease and controlledrelease formulations do notseem tobe pharmacodynamically altered by meals (16, 17 ). Nifedipine and other dihydropyridines have increased oral bioavailability when ingested with grapefruit juice evidenced by hypotension and tachycardia ( 18,19 ). This effect is not seen in the other classes of calcium channel blockers such as diltiazem and verapamil (20,21 ). Avoidance of grapefruit juice or altematives to the dihydropyridines should be considered in those patients using calcium channel blockers.