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• Useful in Black patients – Mechanism of action - prevents hypervolemia
• Initially decreases blood volume and fluid in tissues
– Causes increased Na+ excretion and water follows • appears to also relax blood vessels – Side or toxic effects
• potassium depletion (causes arrhythmias)
• may aggravate diabetes mellitus
– thiazides seem to inhibit insulin secretion – Contraindications or Cautions
• possibly diabetes
• renal or liver disease (somehow thiazides aggravate condition)
• cardiac arrhythmias (because of K+ depletion) Summary of Antihypertensive Drugs
• Control of hypertension difficult – all effective agents produce significant side
– Mild hypertension use - weight control, avoid
salt, possibly exercise.
– When drug therapy required, usually use 2 or
more drugs - helps avoid side effects.
• hydralazine (relaxes vessels directly but causes reflex tachycardia) with
propranolol (β blocker - lower B.P. and also reduces tachycardia)
• or a diuretic with any other kind of agent. Hypertensive emergencies
• Classically Use I.V. medicines that relax blood vessels
• Diazoxide (Hyperstat®) - given I.V. push or drip- used with a
diuretic, relaxes arteries and venules possibly by
• Sodium Nitroprusside (Nipride®) - I.V. drip - requires
constant attention - relaxes arteries and venules
• Labetolol IV (alpha and beta blocker)- easily countered with
specific antidotes, can be followed with oral form. • Oral Agents Becoming Popular
• Clonidine - central sympathetic blockade- takes 30-60
minutes to lower BP. Used in office.
• Nifedipine capsule - calcium channel blocker- break open
and put under tongue. Onset in seconds. BP near normal
in 30 minutes.
• Captopril - ACE Inhibitor (RAA). Many emergencies are
due to an overactive renin-angiotensin system. This agent
works in minutes. Antihypotensive Agents
• Mechanism of Action - to increase BP by:
– Increased peripheral resistance α agonist
• phenylephrine (for spinal anesthesia) or dopamine – Increased cardiac output -beta agonists
• isoproterenol (a β agonist - for shock)
– *Sometimes use drugs that are both alpha & beta agonists,
eg. ephedrine (for...
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This document was uploaded on 02/07/2014.
- Spring '14