renal3 Flashcards
Regulation of Blood Pressure
Blood pressure is the product of cardiac output (C.O.) and peripheral vascular resistance (P.V.R.). Factors affecting C.O.: inotropic state of cardiac muscle; heart rate; filling pressure. These factors are influenced by sympathetic and parasympathetic activity, circulating hormones, intrinsic cardiac muscle function, volume regulatory hormones, renal function, volume intake, posture. Factors affecting P.V.R: sympathetic and parasympathetic activity; vasoconstrictor and vasodilator hormones, blood viscosity, blood volume, cardiac function.
ACE Inhibitors Mechanism of Action
Inhibits converting enzyme activity; blocks the conversion of angiotensin I to angiotensin II, preventing angiotensin II-mediated vasoconstriction and stimulation of aldosterone release. Blocks degradation of bradykinin. Bradykinin (along with Substance P) cause bronchoconstriction and stimulate irritant receptors.
Adverse Effect of ACEI
Cough (approx. 20%) -hyperkalemia - Contraindicated in pregnancy. mild increase in serum creatinine (contraindicated with bilateral renal artery stenosis), angioedema (rare) –anemia (rare)
Uses of ACEI
HTN -heart failure -chronic kidney disease -diabetic nephropathy
Angiotensin II Receptor Blockers (ARBs)
Losartan, irbesartan, candesartan, valsartan
Mechanism of Action of ARBS (Losartan, irbesartan, candesartan, valsartan)
Irreversibly blocks the actions of angiotensin II at AT1 receptor. Prevents angiotensin II-mediated vasoconstriction, aldosterone release
Adverse Effect of ARBS
Similar to ACE inhibitors except cough not seen - may be associated with lower hyperkalemia · HTN -heart failure -chronic kidney disease -diabetic nephropathy
Calcium Channel Blockers
Dihydropyridines (DHP): amlodipine, nislodipine, nifedipine, felodipine
Non-dihydropyridines (NDHP): diltiazem, verapamil
Mechanism of Action of Calcium channel blockers
Cause arterial vasodilation and lower peripheral vascular resistance by blocking L-type calcium channels. Dihydropyridines (DHP) are more selective to blocking L-type Ca channels in blood vessels while verapamil
binds equally to cardiac and vascular L-type Ca channels. Non-dihydropyridines, decrease conduction through AV node and have moderate negative chronotropic and
inotropic actions.
Pharmacokinetics of Calcium channel blockers
Readily absorbed, extensively protein bound, metabolized by the liver to inactive metabolites. Drug interactions NDHP»_space;>DHP
NDHP – inhibit and are metabolized by Cytochrome P450 3A4 system
Examples: atorvastatins (and other statins), amiodarone, cyclosporine, carbamazepine, warfarin,
grapefruit juice, St. Johns wort, phenytoin, ritonavir (and other protease inhibitors), erythromycin (and other macrolides).
DHP – metabolized and mild inhibitor of cytochrome P450 3A4 system. Prolonged half-life allows for once daily dosing (diltiazem, and verapamil have long acting formulations)
Adverse Effect of Calcium channel blockers
Non-DHP: nausea -headache -constipation -gingival hyperplasia -conduction defects (contraindicated in 2° or 3° heart block).
DHP:
- peripheral edema -reflex tachycardia -flushing, headache -gingival hyperplasia.
Uses DHP of Calcium channel blockers
HTN, migraine prophylaxis NDHP: HTN, migraine prophylaxis, angina, rate control for atrial fibrillation
Beta Blockers
Selective beta 1 (cardio) receptor blockers: atenolol, metoprolol
Non-selective beta 1 and beta 2 (located in bronchial and vascular system) blockers: propranolol, timolol Beta and alpha blocker: carvedilol, labetalol
Mechanism of Action of beta blockers
Beta-1 selective beta-adrenergic receptor blocking agents compete with catecholamines at peripheral adrenergic neuron sites, block cardiac receptors to decreased cardiac output, and suppression of renin activity. Bind to receptors in cardiac nodal tissue, the conducting system, and contracting myocytes
Agents with intrinsic sympathomimetic activity (ISA) have a lower propensity to negatively influence cardiac output or heart rate at rest. ISA or partial agonist activity is mediated directly at adrenergic receptor sites and is manifested by a smaller reduction in resting cardiac output and resting heart rate. examples: Labetolol and Acebutolol
Adverse Effect of beta blockers
fatigue, elevate lipids, mask symptoms of hypoglycemia, sexual dysfunction, and respiratory abnormalities
Uses of beta blockers
post MI/CAD (1st line), angina, glaucoma (ophthalmic), heart failure (metoprolol, carvedilol), rate control in atrial fibrillation, migraine prophylaxis, HTN
Direct Vasodilators
(hydralazine, minoxidil)
Mechanism of Action of direct vasodilators (hydralazine, minoxidil)
peripheral, vasodilating effect through a direct relaxation of vascular smooth muscle. The peripheral, vasodilating effect causes decreased peripheral vascular resistance; and an increased heart rate, stroke volume, and cardiac output. The preferential dilatation of arterioles, as compared to veins, minimizes postural hypotension and promotes the increase in cardiac output. Increase in renin activity in plasma, presumably as a result of increased secretion of renin by the renal juxtaglomerular cells in response to reflex sympathetic discharge. This increase in renin activity leads to the production of angiotensin II, which then causes stimulation of aldosterone and consequent sodium reabsorption.
Hydralazin mechanism of action
alter cellular calcium metabolism, interferes with the calcium movements within the vascular smooth muscle that are responsible for initiating or maintaining the contractile state. Release of nitric oxide from drug or endothelium
Minoxidil mechanism of action
a potassium channel opener, causing hyperpolarization of cell membranes
Pharmacokinetics of Hydralazine
peak plasma levels are reached at 1 to 2 hours. Half-life of 3 to 7 hours. Extensive hepatic metabolism
Pharmacokinetics of Minoxidil
extent and time course of blood pressure reduction do not correspond closely to its plasma concentration. half life = 4.2 hours
Adverse Effect of hydralazine, minoxidil
Headache, anorexia, nausea, vomiting, diarrhea, palpitations, tachycardia Hydralazine: SLE –like symptoms
Minoxidil: reflex tachycardia and salt/H20 retention (3 drug drug), hair growth
Uses and dosing of hydralazine, minoxidil
3 or 4th line agents Hydralazine: HTN, heart failure Minoxidil: HTN, hair growth (topical)