Propranolol Amiodarone

Fig. 20.13. Potential H-bonding energy, released upon interaction with the transmembrane domains of P-gp (in arbitrary energy units, EU) for progesterone (1), propranolol (2), amitriptyline (3), diltiazem (4), amiodarone (5), colchicine (7), gramicidin S (8), daunorubicin (9), vinblastine (10), cyclosporin A, in comparison with verapamil...

Drugs that may affect procainamide include amiodarone, anticholinergics, antiarrhythmics, beta-blockers, ethanol, histamine H2antagonists, propranolol,... 

Drugs that may affect flecainide include amiodarone, cimetidine, cisapride, disopyramide, propranolol, ritonavir, urinary acidifiers/alkalinizers, and verapamil. Smoking may also have an effect. Drugs that may be affected by flecainide include cisapride, propranolol, and digoxin. 

Drugs that may affect HMG-CoA reductase inhibitors include alcohol, amiodarone, antacids, azole antifungals, bile acid sequestrants, cimetidine, cyclosporine, diltiazem, erythromycin, gemfibrozil, isradipine, nefazodone, niacin, nicotinic acid, omeprazole, phenytoin, propranolol, protease inhibitors, ranitidine, rifampin, St. John s wort, and verapamil. 

Methimazole (Tapazole) [Antithyroid Agent] Uses Hyperthy-roidism, thyrotoxicosis, pr for thyroid surgery or radiation Action Blocks T3 T4 formation Dose Adults. Initial 15-60 mg/d PO tid Maint 5-15 mg PO daily Peds. Initial 0.4-0.7 mg/kg/24 h PO tid Maint V h- U h of initial dose PO daily w/ food Caution [D, +/-] Contra Breast-feeding Disp Tabs SE GI upset, dizziness, blood dyscrasias Interactions t Effects OF digitalis glycosides, metoprolol, propranolol X effects OF anticoagulants, theophylline X effects W/ amiodarone EMS None OD May cause N/V, HA, abd pain, fever, and pale skin symptomatic and supportive... 

Classes I, III, and IV all involve transmembrane ion channels Classes I and III involve Na+ channels. Class I compounds are designed to block cardiac Na channels in a voltage-dependent manner, similar to local anesthetics. Not surprisingly, many of these Class I agents are either local anesthetics or are structurally based on local anesthetics. Class I compounds include procainamide (7.15), disopyramide (7.16), amiodarone (7.17), lido-caine (7.5), tocainide (7.18), mexiletine (7.19), and flecainide (7.20). The majority of these compounds possess two or three of the fundamental structural building blocks found within local anesthetics. Propranolol (7.21) is the prototypic Class II agent. Class III compounds include molecules that block outward K channels, such as sotalol (7.22) and dofetilide (7.23), and molecules that enhance an inward Na current, such as... 

Simvastatin (Zocor) [Anrilipemic/HMG-CoA Reductase Inhibitor] Uses X Cholesterol Action HMG-CoA reductase inhibitor Dose Adults. 5-80 mg PO w/ meals X in renal insuff Peds. 10-17 y 10 mg, 40 mg/daily max Caution [X, —] Avoid concurrent use of gemfibrozil Contra PRG, liver Dz Disp Tabs 5,10, 20, 40, 80 mg SE HA, GI upset, myalgia, myopathy (muscle pain, tenderness or weakness w/ creatine kinase 10 x ULN), Hep Interactions T Effects OF digoxin, warfarin T risk of myopathy/iiiabdomyolysis W/ amiodarone, cyclosporine, CYP3A4 inhibitors, fibrates, HIV protease inhibitors, macrolides, niacin, verapamil, grapefruit juice X effects W/ cholestyramine, colestipol, fluvas-tatin, isradipine, propranolol EMS T Effects of warfarin use amiodarone and... 

Although the antiarrhythmics have been entered into this classification according to a characteristic major action, most have other effects as well. For example, quinidine (class I) has major class III effects propranolol (class II) has minor class I effects, and sotalol (class II) has major class III effects. Amiodarone has class I, II, III and IV effects but is usually classed under III. 

The safety and efficacy of amiodarone for supraventricular tachycardia have been studied in 50 infants (mean age 1.0 month, 35 boys) (222). They had congenital heart disease (24%), congestive heart failure (36%), or ventricular dysfunction (44%). Six, who were critically ill, received a loading dose of intravenous amiodarone 5 mg/kg over 1 hour, and all took 20 mg/kg/day orally for 7-10 days, followed by 100 mg/day if this failed to control the dysrhythmia, oral propranolol (2 mg/kg/day) was added. Follow-up was for an average of 16 months. Rhythm control was achieved in aU patients. Growth and... 

When salbutamol is used to arrest premature labor, effective doses are likely to produce mild fetal tachycardia (for example an increase of 20/minute) (23). In one case, supraventricular tachycardia occurred in the fetus in the 34th week of pregnancy after the mother had been treated with salbutamol digoxin with and without propranolol was ineffective, but amiodarone controlled the tachycardia (24). 

Clinically important, potentially hazardous interactions with acebutolol, amiodarone, aspirin, atenolol, atorvastatin, betaxolol, carbamazepine, carteolol, celiprolol, donidine, dabigatran, dantrolene, digoxin, dofetilide, epirubicin, eplerenone, erythromycin, esmolol, eucalyptus, everolimus, lovastatin, metoprolol, mistletoe, nadolol, oxprenolol, penbutolol, pindolol, propranolol, quinidine, ranolazine, sibutramine, simvastatin, timolol, trabectedin... 

The most frequent offenders are cytostatic agents and anticoagulants, but hair loss can occur with a variety of common drugs, including hormones, anticonvulsants, amantadine, amiodarone, captopril, cholesterol-lowering drugs, cimetidine, colchicine, etretinate, isotretinoin, ketoconazole, heavy metals, lithium, penicillamine, valproic acid, and propranolol. 

Answer E. Increased sympathetic activity is a major problem in hyperthyroidism and is best managed by use of beta blockers, which can offset cardiac stimulatory effects. Propranolol has an ancillary action in thyrotoxicosis in that it prevents conversion of T4 to T3 via its inhibition of 5 deiodinase. Amiodarone causes difficult-to-predict adverse effects on thyroid function and would not be appropriate in a patient with hyperthyroidism. Bretylium is an IV agent reserved for ventricular arrhythmias. Digoxin is not ideal because of its complex actions on the heart, which include both inhibition and stimulation. 

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