0071643192.pdf

TOXICOLOGY

b-Blockers

Normal function of β-adrenergic receptors:

■ β-1: Heart (increases rate, contractility, conduction), kidney (increased
secretion of renin), eye (increased production of aqueous humor)
■ β-2: Smooth muscle relaxation
■ β-3: Adipose tissue (lipolysis)

MECHANISM/TOXICITY

■ β-Adrenergic receptors blockade

SYMPTOMS/EXAM

■ Varying degrees of hypotension, bradycardia
■ Patient may present in cardiogenic shock.
■ Respiratory depression, apnea
■ QRS and QT prolongation
■ Bronchospasm (β-2) in susceptible patients, respiratory depression, and
apnea

TABLE 6.14. Overview of Antidysrhythmic Agents

VAUGHN-WILLIAMS

CLASSIFICATION MECHANISM OFACTION EXAMPLES SYMPTOMS OFTOXICITY TREATMENT

Class I Fast Na+channel IA: Vary with agent Supportive care

blockers→ stabilization Procainamide Agitation, confusion Activated charcoal (if early)

of membranes. Quinidine Hypotension Sodium bicarbonate

Disorpyramide Ventricular or brady- for QRS widening

IB: dysrhythmias

Lidocaine

Phenytoin

IC:

Flecainide

Propafenone

Class II β-Blockers See text See text See text

Class III K+channel blockers → Amiodarone Vary with agent Supportive care

prolongation of Sotolol Hypotension and Activated charcoal (if early)

repolorization. bradycardia Gastric lavage (if early

Sotalol also has QT prolongation → VT, Vfib, sotalol)

β-blocking activity. torsades. Sodium bicarbonate for

Chronic amiodarone QRS widening

therapy: interstitial

pneumonitis, grey or

bluish skin changes,

corneal microdeposits

Class IV Calcium channel blockers See text See text See text