Antihypertensives Flashcards
Joint Nat. Committee says we should treat what BP for someone with DM/kidney disease and what BP without? What do they say is first-line therapy?
Over 140/90 without DM/kidney disease
Over 130/80 with DM/kidney disease
First line therapy = thiazide diuretic
What antihypertensives are these patients on..
- HF
- MI
- High CVD risk
- HF: Thiazide diuretic, B-blocker, ACEI, ARB, aldosterone antagonist
- MI: B-blocker, ACEI, aldosterone antagonist
- High CVD risk: Thiazide, B-blocker, ACEI, CCB
What antihypertensives are these patients on..
- DM
- CKD
- Stroke prevention
- Isolated systolic HTN
- DM: Thiazide diuretic, B-blocker, ACEI, ARB, CCB
- CKD: ACEI or ARB
- Stroke prevention: Thiazide diuretic, ACEI
- Systolic hypertension: Thiazide, CCB
Hypertensive urgency vs. crisis?
DBP over 120
Urgency with evidence of organ damage (BUN/creat inc)
Crisis with evidence of organ failure
Why wouldn’t we want a pt to take ACEI before surgery?
ACEI decrease preload leading the patient to be hypovolemic
Angiotensinogen, secreted by the ____ -> (Renin, secreted by the ____) -> AT1 -> (ACE) -> AT2 -> Aldosterone
What effects Do AT2 and Aldosterone have on preload/afterload?
Angiotensinogn by liver
Renin by kidney’s juxtaglomerular cells
Aldosterone INC preload
AT2 INC afterload (potent vasoconstrictor)
ACEI uses?
HTN, CHF, mitral regurgitation, post MI, diabetic neuropathy, CRI
More effective in DM patients
Reduces BP and cardiac load
What are some Angiotensin-1 receptor effects (belong to G-protein coupled receptors)?
Vasoconstriction (especially in afferent arterioles of glomeruli)
Increase NE release
Proximal tubular reabsorption of Na
Secretion of aldosterone from adrenal cortex
ACEI MOA? Name a few.
Block conversion of AT1 to AT2 through interaction with zinc ion of ACE (in endothelium)
Prevents vasoconstriction, sodium retention and SNS stimulation
PRILS! Lisinopril, captopril (capoten), ramipril, enalapril (vasotec), fosinopril, quinapril, benazepril
What’s the major difference between ACEI? Captopril vs. enalapril vs. lisinopril
Captopril onset 15-30 min, DOA 6-10h, E1/2t 2h (more redosing)
Enalapril onset 1-2h, DOA 18-30h (no rash/renal insufficiency bc lacks sulfhydryl group)
Lisinopril onset 1h, DOA 18-30h
ACEI side effects?
Note: in general, they are mild, good compliance
Prolonged hypotension intra-op!!! (Don’t have them take it before surgery!!)
Granulocytopenia, angioedema, proteinuria, persistent cough, hyperkalemia
Captopril: rash, loss of taste
ACEI contraindication?
Renal artery stenosis (bc patients may develop renal failure due to efferent arteriole constriction)
ARB MOA? Name some.
Competitive binding to inhibit AT2 at its receptor, blocks AT2 without effecting ACE activity, results in decreased peripheral vasoconstriction
SARTAN! Losartan (cozaar), valsartan (diovan), irbesartan, candesartan, telmisartan, eprosartan
ARB side effects and contraindication?
SE: similar to ACEI but less cough and no bradykinin accumulation
CI: renal artery stenosis, pregnancy
Hydralazine is a ____ derivative, what does this do? Does it work more on arteries or veins?
Arterial vasodilator. Phthalazine derivative which activates gaunylate cyclase producing relaxant effect on vascular smooth muscle.
ARTERIES > VEINS
Hydralazine dose? When does it peak?
2.5-10 mg IV
10-20 min peak (this is a LONG time in surgery), lasts up to 6h
Hydralazine pharmacokinetics?
Extensive hepatic first pass metabolism
Onset 15 min, give slow
E1/2t 3h
15% unchanged in kidney
Hydralazine side effects?
Reflex tachycardia! Tachyphylaxis, tolerance DBP reduced more than SBP Dec SVR Inc HR, SV, CO Na/ H2O retention, EKG changes, angina Drug induced lupus- rash, joint pain
Minoxidil MOA, uses?
Directly relaxes ARTERIAL smooth muscle (little effect on venous) by increasing influx of K into smooth muscle, hyperpolarize, vasodilate
Used to treat HTN due to renovascular disease, renal failure, transplant rejection
Minoxidil pharmacokinetics?
90% oral dose absorbed from GI
Peak in 1 h
E1/2t 4h
10% unchanged in urine
Minoxidil side effects?
Inc HR, CO
Inc plasma concentration of NE, renin (retains Na/H2O, weight gain, edema, hypertrichosis, pulm HTN, pericardial effusion)
Abnormal EKG (flat/inverted T wave)
What are peripheral vasodilators used for? Name some.
Facilitates forward LV flow in AR, MR, HF
Controlled hypotension in OR
Treat hypertensive crisis
Nitroglycerine, nitroprusside, isosorbid, dipyridamole, papverine, trimethaphan, diazoxide, adenosine
SNP (sodium nitroprusside, nipride) class? In general, what does it do?
Nonselective peripheral vasodilator, direct acting
Relaxes arterial and venous vascular smooth muscle
Lacks effects on nonvascular smooth/cardiac muscle
SNP MOA?
Interacts with oxyhemoglobin, dissociates immediately to form methemoboin and releases NO and cyanide
NO activates guanylate cyclase, increasing cGMP
cGMP inhibits calcium entry to vessels, increases uptake of Ca into ER resulting in vasodilation
SNP metabolism?
Transfer an electron from Fe of oxyhemoglobin to SNP yields metHGb and SNP radical where all 5 cyanide ions are released, one of these ions reacts with metHGb to form cyano-methemoblobin (nontoxic), the remainder is metabolized in liver and kidney converted to thiocyanate (if they are on it too long, this leads to cyanide toxicity)
Cyanide toxicity: signs and treatment?
Can occur at over 2 mcg/kg/min for long periods
Pt is resistant to hypotensive effects, tachyphylaxis, this may precipitate tissue anoxia, anaeorobic metabolism, and lactic acidosis (get lactic level drawn)
Treat by stopping SNP, 100% O2, sodium bicarb, sodium thiosulfate, sodium nitrate for severe toxicity
Signs of SNP-induced thiocyanate toxicity or methemoglobinemia?
Thio toxicity: rare, less toxic than cyanide, s/s: N/V, tinnitus, fatigue, CNS hyperreflexia, consfusion, physchosis, miosis, seizure, coma
Methemoglobinemia: rare, impaired O2 with adequate CO
Phototoxicity is also possible, comes in dark bag so light doesn’t convert the SNP to hydrogen cyanide
SNP dose
0.3 mcg/kg/min - 10 mcg/kg/min
0.3-0.5 for controlled hypotension, 1-2 mcg/kg for hypertensive crisis
Max should not be given for more than 10 min, immediate onset, short duration of action, put in an A-line for close monitoring!!
SNP cardiac, CNS, pulmonary, and blood effects?
CV: venous/art dilation, dec venous capacitance (due to venous return), baroreceptor reflex inc HR, dec SBP/SVR/PVR, inc contractility, does NOT dilate coronary artery so consider coronary steal
CNS: inc CBF/ICP
Pulm: stops hypoxic vasoconstriction
Blood: inc intracellular GMP which inhibits platelet aggregation and bleeding time
Nitroglycerin (NTG) class, in general what does it do?
Organic nitrate that acts on venous capacitance vessels and large coronary arteries
Peripheral vasodilator
NTG MOA?
Generates NO through a glutathione-dependent pathway (that involves glutathione and glutathione S-transferase)
It requires the presence of thio-containing compound to generate NO
NO generation stimulates cGMP to cause peripheral vasodilation (like SNP)
How does NTG form metHGb? How is methemoglobinemia treated?
Nitrite metabolite oxidizes ferrous ion in Hgb to ferric form that leads to formation of metHgb (makes pulse ox go down)
Methemoglobinemia can be treated with methylene blue 1-2 mg/kg IV over 5 min
Tolerance to NTG starts after how long?
24 hours of sustained treatment
NTG effects of CV?
Venodilation, dec venous return, dec preload, dec L/R EDP, dec CO, so REDUCES myocardial oxygen requirements
(No change in HR/SVR)
Increase in coronary blood flow to subendocardial areas (opposite of SNP)
Good for angina, cardiac failure, and controlled hypotension (4-5 mcg/kg/min)
NTG effects on CNS, pulmonary, blood, GI?
CNS: vasodilation, increased ICP headache
Pulmonary: dec PVR, bronchial dilation, inhibits hypoxic pulmonary vasoconstriction
Blood: dose related prolonged bleeding time, inhibits platelet aggregation
GI: relaxes smooth muscles of GI (good for biliary spasm)
Isosorbid key points?
Oral nitrate, not used over NTG; just know it exists
Works on venous circulation, improves regional distribution of myocardial blood flow in pt with CAD
SE orthostatic hypotension
Active metabolite isosorbid-5-mononitrate
Trimetaphan key points?
Peripheral vasodilator, rapid onset
Lowers BP, CO, SVR
Inc HR due to PSNS blockade
Not better than NTG or SNP; Just know it exists
What do phosphodiesterase inhibitors do?
Isoenzymes that inhibit the breakdown of intracellular cAMP and cGMP causing vascular smooth muscle relaxation (vasodilation) and positive inotropy
What are phosphodiesterase inhibitors used for? Which drugs are contraindicated? Name a couple phosphodiesterase inhibitors.
Used for heart failure
Avoid nitrates or ED meds
Amrinone, milrinone
How do calcium channel blockers work?
CCB bind to receptor on voltage-gated Ca ion maintaining the channel in a inactive or closed state
Where are calcium ion channel present?
Cell membranes of skeletal muscle Vascular smooth muscle Cardiac muscle Mesenteric muscle Neurons Glandular cells
CCB with phenyl-alkyl-amines or benzothiazepines structure will block the _____. CCB with 1,4-dihydropyridines will block _____.
phenyl-alkyl-amines or benzothiazepines structure block AV node
1,4-dihydropyrides block arterial beds
What effects do CCB have?
Dec contractility (ionotropy)
Dec HR (chronotropy)
Dec activity of SA node
Dec rate of conduction of impulses via AV node (dromotropy)
Dec SVR and BP (vascular smooth muscle relax, art > venous)
CCB side effects?
Prolonged bleeding
GI constipation
Cardiac problems
CAncer
CCB uses?
Systemic and pulmonary HTN Cerebral arterial spasm Raynaud's disease Migraine Bronchial asthma, esophageal spasm, dysmenorrhea, premature labor
CCB drug interactions?
Inhalational agents, B-blockers- myocardial depression, vasodilation
Potentiate NM blockers
LA toxicity (verapamil)
Dantrolene with verapamil can cause hyperK
Interacts with platelet function (causes prolonged bleeding)
Digoxin plasma conc inc with CCB
H2 antagonists (ranitidine and cimetidine) inc CCB plasma levels
Toxicity of CCB reversed with what?
IV calcium or dopamine
What is verapamil, where does it primarily work?
Derivative of papaverine, specific for slow calcium channel
Primary site of action: AV node; Depress AV node, neg chonotropic, neg inotropic, moderate vasodilation on coronary and systemic arteries
Verapamil uses?
SVT, vasospastic angina, HTN
Hypertropic cardiomyopathy
Maternal and fetal tachydysrhythmias
Premature onset of labor
Verapamil pharmacokinetics?
Highly protein bound (presence of agents like lidocaine/diazepam inc its activity)
Orally almost completely absorbed, extensive hepatic first pass metabolism, almost none of the drug appears unchanged in the urine (limited bioavailability)
Oral peaks in 30-45 min, IV in 15 min
E1/2t 6-12h
What is nifedipine? What is it used for? What effects does it have?
Dihydropyridine derivative used for angina
Primary site of action is peripheral arterioles (vasodilates more than verapamil, little/no effect on SA/AV node)
Dec SVR/BP
Reflex tachycardia
Myocardial depression on pts with LV dysfunction or on B-blockers
Nifedipine and nicardipine mostly work where?
Coronary and peripheral artery vasodilation
Diltiazem works where? Uses?
Benzothiazepine derivative; principle site of action is AV node
Uses: (similar to verapamil but less potent) SVT, HTN, vasospastic angina, hypertrophic cardiomyopathy, maternal/fetal tachydysrhythmias
What is the only CCB with an active metabolite?
Verapamil
Clonidine MOA
It is a centrally acting agent; reduces sympathetic outflow from vasomotor centers in the brainstem
Centrally acting selective partial alpha-2 adrenergic agonist
(200:1 A1 over A2)
Clonidine uses?
Hypertension (it dec BP from dec CO due to dec HR/PVR)
Induce sedation, analgesia
Dec anesthetic requirements (DEC your MAC by 50%!!)
Improve peri-op hemodynamics
Clonidine SE and what happens if it is stopped abruptly?
If stopped abruptly, rebound HTN. Withdrawal after 18 hours of no use, lasts 24-72 hours if pt on doses over 1.2 mg/day, treat with clonidine
SE: bradycardia, sedation, xerostomia (dry mouth), nightmares, depression, vertigo, EPS, lactation in med
Should a patient continue using B-blockers, CCB, or ACE pre-op?
B-blocker: YES, if not they care at risk of peri-operative MI
CCB: YES unless severe LV dysfunction
ACEI: NO (hypovolemia intra-op)
