Pharmacology

Question 1

Ivabradine slows heart rate (negative chronotropic effects) with no effect on cardiac contractiility (inotropy) and/or relaxation (lusitropy)

It slows the rate of SA node firing by selective inhibitoon of funny sodium channels, thereby prolonging the slow depolarization of phase 4

Answer 1

Class III antiarrhythmic drugs block the K+ channels, including slow delayed rectifier channels (I_ks) and thereby prolong erpolarization, action potential duration, and the refractory period

Question 2

Class I antiarryhthmics (e.g. procainamide, flecainide) act by blocking the sodium channels (I_Na) and inhibiting phase 0 depolarization of the myocardial action potential

They slow action potential conduction velocity but do not significantly affect heart rate

Answer 2

CCBs inhibits the L-type calcium channels (I_Ca-l) responsible for phase 2 (cardiomyocyte action potential) and phase 0 (nodal action potential) depolarization. They slow the sinus rate, prolong conduction through the AV node, and depress myocardial contractility (negative inotropic effect)

Question 3

Digoxin inhibits the NaK exhanger in myocardial cells, increasing intracellular sodium. This in turn leads to a rise in intracellular calcium due to the Na-Ca exchanger, resulting in impaired contractility and left ventricular systolic function

Question 4

Answer 4

Question 5

Facial flushing and pupillary dilation are common findings in pts taking anticholinergics (and specifically blockade of muscarinic receptors)

Due to blockade of eccrine sweat gland causes fever and compensatory cutaneous vasodilation

Question 6

Metyrapone blocks 11B-hydroxylase, which converts 11-deoxycortisol to cortsol in the zona fasciculata. because 11-deoxycortisol lacks glucocorticoid activity, it does not inhibit pituitary ACTH secretion via neg feedback.

As a result, blocking cortisol with metyrapone can cause a spike in pituitary ACTH secretion, leading to more 11-deoxycrtisol production, which is excreted as 17-hydroxycorticosteroids in urine

Question 7

CYP inducers (decrease warfarin effectiveness):

Carbamazepine, pehnytoin, ginseng, St. John Wort, OCP, Phenobarbital, Rifampin

Answer 7

CYP inducers (increase warfarin effectiveness):

Acetaminophen, NSAIDS

ABX/Antifungals

Amiodarone

Cimetidine

Cranberry Juice

Omeprazole

Thyroid hormone

SSRIs

Question 8

Levodopa can cross the BBB unlike dopamine, but is largely metabolized so is usually given with carbidopa, a peripheral DOPA decarboxylase inhbitor

and Entacapone, a COMT inhibitor, if needed