These drugs may act at any combination of the following sites: - The vessel wall unrelated to nerve ending e.g. diazoxide, hydrallazine, nitrates, nitrities.
- The sympathetic receptor - Beta blockers, e.g. propranolol, metoprolol.
- The post ganglionic sympathetic nerve endings e.g. guanethidine, reserpine.
- Sympathetic autonomic ganglia.
- The CNS (the brain stem) e.g. reserpine, methyl-dopa.
- Blood volume.
TREATMENT PROTOCOL ANGIOTENSIN CONVERTING ENZYME INHIBITORS Angiotensin - converting enzyme inhibitors inhibit the conversion of angiotensin I to angiotensin II therapy causing peripheral vasodilation. They also block the production of aldosterone resulting in sodium and water excretion and the retention of potassium. They should be used when thiazides and beta-blockers are contraindicated or where they fail as first line therapy. ACEIs may cause a rapid fall in blood pressure in some patients on thiazides, therefore discontinue thiazides 3 days before starting therapy with an ACEI. Even though ACEIs have greater activity in patients with high renin levels, low doses of ACEIs and thiazides produce a similar effect in patients with low renin levels. ACEIs have been shown to reduce mortality in heart failure. May cause some regression of left ventricular hypertrophy. Use with caution in patients with renal disease as ACEIs may occasionally cause impairment of renal function. ACEIs may cause fetal or neonatal death or injury when used during the second or third trimester of pregnancy. When pregnancy is detected discontinue the ACEI as soon as possible. DRUG INTERACTIONS - Loop and Thiazide Diuretics: Postural hypo-tension.
- Potassium Sparing Diuretics\Potassium Supplements|Trimetho-prim: hyperkalemia. Monitor potassium level. Caution patients against use of potassium containing salt substitutes or diet supplements.
- Allopurinol: Steven Johnson’s Syn-drome, skin erup-tions, anaphylactic coronary spasm. Monitor patients for hypersentivityreac-tions e.g. pruritus, chest pain, hypoten-sion or broncho-spasm
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