University:
University of North Carolina at Chapel Hill
Course:
NURS 312 | Pharmacology
Academic year:

2020
Views:

378

Pages:

1
Author:

kundgetanufv

4.3 – “Tre “Tress Amigos”: Class III Antiarrhythmic Antiarrhythmicss – K+ channel b blockers lockers • Class III antiarrhythmics include Amiodarone (tres amigos), ibutilide, dofetilide (“Till I Die” sign for -tilide suffix), sotalol (soda bottles). (AIDS mnemonic for all four.) • Recall that outward K+ current is present in plateau & repolarization phases of cardiac myocytes, and is the main driver of the latter. By blocking K+ currents, depolarization takes longer (i.e. prolonged refractory period; prolonged phases 2 & 3), and AP is prolonged (banana curtain pushed away). • Clinical indications: o Used primarily for rhythm control, along with Class I. Not used for rate control, unlike Classes II & IV. o AP prolonging effects can be used to suppress both ventricular & supraventricular arrhythmias (Heart lamps illuminated on top & bottom). o Can be used for cardioversion in AFib (man changing channels on fibrillating TV) • Amiodarone o shares characteristics of Class 1-4 arrhythmias (uno, dos, tres, quatro). Blocks inactivated Na+ channels. Weak β adrenergic & calcium blocking effects o Side effects/toxicities ▪ Neurologic: tremor, ataxia, peripheral neuropathy, sleep disturbances (brained skull embroidery on hats) ▪ Gray corneal microdeposits seen in almost all patients within a matter of weeks (silver sunglasses). Generally asymptomatic; may rarely cause halos in peripheral vision, optic neuritis, or blindness. ▪ 40% inorganic iodine by weight (hence the name amiodarone), which can cause hyper- or hypothyroidism (various sized bowties = variable effects). Mediates two types of hyperthyroidism: • Type 1: found in patients with existing or unrecognized thyroid goiters. Excess iodine allows ↑↑ production of thyroid hormones. • Type 2: thyroiditis may result as a direct toxic effect of the drug, causing temporary increase in T3 & T4 d/t dumping of stores, and subsequent ↓production. • Important to get baseline thyroid function tests before initiating medication & to monitor thyroid function while on amiodarone. ▪ Pulmonary toxicity may lead to fatal restrictive fibrosis (fibrotic lung embroidery, with button restricting movement) ▪ Heart block (hat shielding heart) ▪ Many other heart effects, including HF, especially with rapid IV administration (failed balloons) ▪ Can cause QT prolongation (as do all the drugs with the banana curtain in the back). However, has very low rate of torsades occurrence, maybe because of effects on many different ion channels • Contrast with all the others in this class, which also have prolonged QT interval, with dose related incidence of torsades (twisted streamers throughout sketch) ▪ Hypersensitivity hepatitis; abnormal LFTs (hepatic liver shaped spot on cow) ▪ Skin deposits → photodermatitis, with a gray blue discoloration in sun exposed areas (photographer; gray-blue suits) ▪ Inhibitor of CYP450 (trailer with license plate) • Sotalol (soda bottles) o Also a β-blocker, hence the -lol suffix (blocked β bugle)