52, Chapters 53
Antidysrhythmics Antianginals
Cardiac GlycosidesDigoxin (Lanoxin)
Treatment of atrial fibrillation 2nd line drug to treat heart failure
Digoxin
Functions
positive inotropic action negative chronotropic action negative dromotropic action increase stroke volume
Digoxin
Digoxin
Drug interactions
Herbal interactionsSt John's Wort
decreases effectiveness of dig by 25%
Highly toxic with low serum potassium Potassiumwasting diuretics & Glucocorticoids
Antidote for digitalis toxicity
Digoxin Immune FabDigibind
Antianginal Drugs
Types of anginal pectoris
Antianginal Drugs (cont'd)
Nonpharmacologic measures to reduce Angina Types of antianginals
Nitrates Betaadrenergic blockers Nonselective and selective betablockers Side effects/adverse reactions (review)
Nitrates
mainstay of antianginal drug tx prophylaxis & treatment multiple routes of administration
sublingual, buccal, chewable, tablets, capsules, ointments, patches, inhalable sprays, & IV's
Oral Nitrates
Administration of Nitroglycerine SL Should "burn" under tongue Stop all activity! Sit quietly
Administration of Nitroglycerine SL
Quick onset; relieves pain within 5 minutes Rule of Thumb:
If after taking 3 sl nitro 5 minutes apart, and NO PAIN RELIEF
CALL 911
Cutaneous Administration of Nitrates (prophylaxis)
Apply to clean area (not breasts) Do not shave hair (OK to clip) Rotate sites Leave off 12 hrs a day (to reduce tolerance)
Examples of Nitro
Nitrobid (IV) NitroDur; Nitrodisc, TransdermNitro (transdermal) Nitrostat (sublingual) (potency deteriorates when opened) Change every 6 months unopened; every 3 opened Oral forms
Other Nitrates
Isosorbide Dinitrate
Isordil
Isosorbide Mononitrate
Imdur, Monoket, & ISMO
Nitrate Side Effects
Dizziness (especially short acting) (take when sitting down) Headache (transient with SL; problematic with PO, patches) Lowered blood pressure Flushing (transient with SL) Tolerance
Antianginal Drugs (cont'd)
Calcium channel blockers (to be discussed with antiarrhythmia drugs
A (amlodipine (Norvasc) Very (verapamil HCl (Calan, Isoptin) Nice (nifedipine HCL (Procardia), Drug (diltiazem HCl (Cardizem)
Antidysrhythmic Drugs (for tachydysrhythmias)
Alter heart's electrical conduction system Goal is to prevent dysrhythmias, relieve symptoms and prolong life Indicated for
Mechanism of action is to reduce automaticity, slow conduction and prolong refractory period
atrial fibrillation and flutter decrease ventricular rate and irregularity
Classifications and Individual Drugs Vaughan Williams Classification Class I Sodium Channel Blockers block the movement of sodium into cells of cardiac conduction system Class IA have a broad spectrum of antidysrhythmic effects and are used for both supraventricular and ventricular dysrhythmias Quinidine is prototype
Class IA
Quinidine* Procainamide Disopyramide used for:
atrial fibrillation, premature atrial & ventricular contractions & (PAC's PVC's), V tach, & WPW (Wolff Parkinson White Syndrome)
Quinidine
Bitter taste Used less today because long term effects with atrial fib increase mortality Irritating to GI track
Disopyramide (Norpace)
Strong anticholinergic SE May cause urinary retention in men with prostate enlargement Not use in patients with glaucoma
Procainamide (Pronestyl)
Short duration of action, must be given every 34 hours Diarrhea sign of toxicity Drug induced syndrome resembling Systemic Lupus Erythematosus
Butterfly rash on face Joint pain
Class 1B Drugs
Lidocaineused for ventricular dysrhythmias after Myocardial Infarction
Given IV (IM in emergency situation) Rapid onset Toxicity: anesthetic properties, numbness, paresthesias,
Class 1B & 1C
1B
1C Drugs used in emergencies
Phenytoin(our old friend Dilantin!) Long half life May require loading dose Never mix IV with D5W Flecainide and papaferonemay initiate new dsyrhythmias or aggravate existing
Antidysrhythmic Drugs (cont'd)
Class II
Class III
Beta adrenergic blockers Prolong repolarization Calcium channel blockers
Class IV
Class II BetaAdrenergic Blockers
Block SNS stimulation of beta receptors in heart and decrease risk of VFib Blocks receptors in SA node and ectopic pacemakers decreasing automaticity Blocks receptors of AV node increases refractory period Effective for management of supraventricular dysrhythmias and those resulting from excessive SNS stimulation
Other Beta Blockers used for dysrhythmias:
Acebutolol given orally for chronic therapy Esmolol has rapid onset and short duration, given IV Propanolol given orally or IV Sotolol noncardioselective beta blocker (class II) that has class III properties
Class III Potassium Channel Blockers
Prolong duration of action potential, slow repolarization, prolong refractory period in both atria and ventricles Amiodarone has electrophysiological characteristics of sodium channel blockers, beta blockers, and calcium channel blockersAdverse effectpulmonary fibrosis When given IV the major effect is slowing conduction in AV node and prolonging refractory period. When given PO prevents recurrent Vtach and fib and to maintain NSR after AF conversion.
Class IV Calcium Channel Blockers
Block movement of calcium into conductile and contractile myocardial cells Reduce automaticity of SA and AV nodes, slow conduction, and prolong refractory period in AV node Effective only in supraventricular tachycardias
Calcium Channel Blockers
Diltiazem and verapamil are the only calcium channel blockers approved for management of dysrhthymias Given IV or PO Do not use IV verapamil with IV propanolol as potentially fatal bradycardia and hypotension
Unclassified Antidysrhythmic Drugs
Adenosine acts like calcium channel blocker by depressing conduction at AV node and is used to restore NSR in clients with PSVT Magnesium sulfate given IV for prevention of recurrent episodes of torsades de pointes and digitalisinduced dysrhythmias