Drugs That Affect Fluid and Electrolyte Balance, Heart and Blood Vessels, and Adrenergic Drugs

Alpha 1 Agonists

Ex: epinephrine, norepinephrine, phenylephrine, dopamine

Therapeutic effects: vasoconstriction, increase BP + SVR, hemostasis, nasal decongestion, mydriasis

Used for: hypotension, nasal sprays

MOA: bind to alpha 1 receptors on VSM

AEs: hypertension, bradycardia, extravasation

Alpha 2 Agonists

Ex: methyldopa, clonidine

Therapeutic effects: CNS depression, vasodilation

Used for: HTN, ADHD, pain, glaucoma, sedation

MOA: presynaptic reduction of sympathetic firing to the heart and blood vessels, causing CNS depression and some vasodilation (stops the outflow of norepi)

AEs: drowsiness, dry mouth, constipation, abuse

**Rebound HTN with abrupt discontinuation of clonidine, wean over 2-4 days

*Methyldopa good for BP control in pregnant pts, no decrease in HR or CO, no fetal harm

Beta 1 Agonists

Ex: dobutamine, isoproterenol

Therapeutic effects: increases HR, CO, contractility, conduction velocity

Used for: heart failure, shock, AV heart block, cardiac arrest

MOA: cause cardiac stimulation by binding to beta 1 receptors

AEs: dysrhythmias, tachycardia, angina

Beta 2 Agonists

Ex: albuterol

Therapeutic effects: dilation of bronchial passages, vasodilation of liver and uterus, glycogenolysis and release of insulin

Used for: asthma, preterm labor

MOA: binds to b2 receptors and cause dilation

AEs: anxiety, tremor, HA, palpitations

*Large dose albuterol loses selectivity and activates b1 receptors

Alpha 1 Antagonists

Ex: prazosin, doxazosin, tamulosin, phentolamine, carvedilol

Therapeutic effects: relaxes blood vessels, lowers blood pressure

Used for: HTN, BPH, pheochromocytoma, HF, Raynaud’s, urinary urgency

MOA: blockade of alpha 1 receptors

AEs: all related to vasodilation: dizziness, HA, orthostatic hypotension, reflex tachycardia, ED, first dose effect/passing out

Beta 1 Antagonists

Ex: atenolol, esmolol, nadolol, propranolol, metoprolol

Therapeutic effects: block epi/norepi causing relaxation, decreased HR and squeeze, heart has more filling time, decreases cardiac oxygen demand

Used for: heart failure, HTN, angina, post-MI, arrhythmias, migraines, anxiety, pheochromocytoma, glaucoma

MOA: bind to beta 1 receptors and inhibit epi/norepi from binding

AEs: bradycardia, decreased CO (titrate up slowly), AV heart block (slows conduction), rebound hypertension/tachycardia

First Generation Beta Blockers

Ex: propranolol, nadolol, sotalol

AEs: wheezing (non-selective, blocks b2 in the lungs too)

Second and third generation become more selective and can help with heart failure, not just HTN

Avoid first generation, non selective beta blockers in pts with COPD or asthma

Drug of Choice for Anaphylactic Shock

Epinephrine!

A1: elevate BP

B1: restore cardiac function in VF, pulseless VT or asystole, can overcome AV block

B2: bronchodilation

Loop Diuretics

Ex: furosemide, bumetanide

Therapeutic effects: decrease fluid volume, decrease cardiac preload, lower blood pressure

Used for: pulmonary edema, edematous states, HTN

MOA: acts on ascending loop of Henle to block reabsorption of Na and Cl

AEs: hypovolemia, hypotension, hypokalemia, orthostatic hypotension, ototoxicity (do not prescribe with other ototoxic meds like aminoglycoside abx)

*Works even with severe renal impairment (thiazides do not)

*Caution with all diuretics during pregnancy

Thiazide Diuretics

Ex: HCTZ

Therapeutic effects: similar to loop diuretics (decrease fluid volume, decrease cardiac preload, lower blood pressure)

Used for: essential HTN, edema, diabetes insipidus

MOA: increase renal excretion of sodium, chloride, potassium, and water (max diuresis less than loop)

AEs: similar to loop diuretics (hypovolemia, hypotension, hypokalemia, orthostatic hypotension) but without ototoxicity

*Not as effective when urine flow is scant (unlike loop)

*Caution with all diuretics during pregnancy

Potassium Sparing Diuretics

Ex: spironolactone, eplerenone (HF)

Therapeutic effects: spare potassium, decreases mortality in HF, little diuretic effect

Used for: HTN, edematous states, HF (decreases mortality)

MOA: blocks aldosterone in the distal nephron, increasing excretion of sodium while retaining potassium

AEs: hyperkalemia, gynecomastia, menstrual irregularities, impotence, hirsutism, deep voice

*Aldosterone keeps Na and rids K

*Used in combo with loop or thiazide to spare K

*K sparing diuretic have similar structure to steroid hormones (bind to endocrine receptors)

*Salt supplements are high in K

*ACEIs, ARBs, and renin inhibitors elevate K

Angiotensin-Converting Enzyme Inhibitors (ACEIs)

Ex: enalapril, captopril

Therapeutic effects: vasodilation, lower blood pressure

Used for: HTN, HF, MI, prevention of MI, stroke, and death in pts at high cardiovascular risk

MOA: blocks/reduces angiotensin II (increases bradykinin), vasovilation, decreased blood volume,

AEs: first dose hypotension, cough, hyperkalemia, fetal injury, angioedema

*Blocking bradykinin causes cough

*Blocking aldosterone elevates K (caution w/ diuretics)

Angiotensin II Receptor Blockers (ARBs)

Ex: azilsartan, losartan, vlasartan

Therapeutic uses: dilates arterioles and vein

Used for:

MOA: blocks angiotensin II

AEs: