Procainamide Cimetidine

PROCAINAMIDE H2 RECEPTOR BLOCKERS Cimetidine may t plasma concentrations of procainamide Cimetidine is a potent inhibitor of organic cation transport in the kidney, and elimination of procainamide is impaired. Cimetidine also inhibits CYP2D6-mediated metabolism of procainamide. Ranitidine is a much weaker CYP2D6 inhibitor Monitor PR and BP at least weekly until stable. Warn patients to report symptoms of hypotension (lightheadedness, dizziness on standing, etc.). Consider alternative acid-suppression therapy... 

Bauer LA, Black D, Gensler A. Procainamide-cimetidine drug interaction in elderly male patients. J Am Geriatr Soc 1990 38(4) 467-9. 

Oct2 Amantandine, memantine, cocaine, desipramine, nicotine, procainamide, cimetidine. O-mefhylisoprenaline, prazosin, reserpine, verapamil... 

Higbee MD, Wood JS, Mead RA. Case report Procainamide-cimetidine intemetion. Apoten-tial toxic interaction in the elderly. J Am Geriatr Soc (1984) 32,162-4. 

Concurrent use of the fluoroquinolones with theophylline causes an increase in serum theophylline levels. When used concurrently with cimetidine, the cimetidine may interfere with the elimination of the fluoroquinolones. Use of the fluoroquinolones with an oral anticoagulant may cause an increase in the effects of the oral coagulant. Administration of the fluoroquinolones with antacids, iron salts, or zinc will decrease absorption of the fluoroquinolones. There is a risk of seizures if fluoroquinolones are given with the NSAIDs. There is a risk of severe cardiac arrhythmias when the fluoroquinolones gatifloxacin and moxifloxacin are administered with drains that increase the QT interval (eg, quini-dine, procainamide, amiodarone, and sotalol). 

When two antiarrhythmic dragp are administered concurrently the patient may experience additive effects and is at increased risk for drug toxicity. When quinidine and procainamide are administered with digitalis, tiie risk of digitalis toxicity is increased. Hiarmacologic effects of procainamide may be increased when procainamide is administered with quinidine When quinidine is administered with the barbiturates or cimetidine, quinidine serum levels may be increased. When quinidine is administered with verapamil, there is an increased risk of hypotensive effects. When quinidine is administered with disopyramide, there is an increased risk of increased disopyramide blood levels and/or decreased serum quinidine levels. 

There is a risk of acute renal failure when iodi-nated contrast material that is used for radiological studies is administered with metformin. Metformin therapy is stopped for 48 hours before and after radiological studies using iodinated material. Alcohol, amiloride, digoxin, morphine, procainamide, quini-dine, quinine ranitidine, triamterene, trimethoprim, vancomycin, cimetidine, and furosemide all increase the risk of hypoglycemia. There is an increased risk of lactic acidosis when metformin is administered with the glucocorticoids. 

Procainamide 12-1 7 mg/kg, no faster than 20 mg/minute 1-4 mg/minute Cimetidine, ranitidine, and trimethoprim inhibit procainamide elimination... 

Which of the following best describes cimetidine s mechanism of interaction with procainamide ... 

The answer is c. (Hardman7 p 906. Katzung, p 1127) Cimetidine inhibits proximal tubular secretion of procainamide, resulting in increased plasma concentrations of procainamide and its active metabolite, N-acetylprocainamide. 

Drugs that may affect lidocaine include beta-blockers, cimetidine, procainamide, tocainide, and succinylcholine. 

Drugs that may affect amiodarone include hydantoins, cholestyramine, fluoroquinolones, rifamycins, ritonavir, and cimetidine. Drugs that may be affected by amiodarone include anticoagulants, beta-blockers, calcium channel blockers, cyclosporine, dextromethorphan, digoxin, disopyramide, fentanyl, flecainide, hydantoins, lidocaine, methotrexate, procainamide, quinidine, and theophylline. Drug/Lab test interactions Amiodarone alters the results of thyroid function tests, causing an increase in serum T4 and serum reverse T3 levels and a decline in... 

T Pancreatic insulin release Metformin Peripheral insulin sensitivity hepatic glucose output/production i intestinal glucose absorption Dose Ist-line (naive pts), 1.25/250 mg PO daily-bid 2nd-line, 2.5/500 mg or 5/500 mg bid (max 20/2000 mg) take w/ meals, slowly T dose hold before 48 h after ionic contrast media Caution [C, -] Contra SCr >1.4 mg/dL in females or >1.5 mg/dL in males hypoxemic conditions (sepsis, recent MI) alcoholism metabolic acidosis liver Dz Disp Tabs SE HA, hypoglycemia, lactic acidosis, anorexia, N/V, rash Additional Interactions T Effects W/ amiloride, ciprofloxacin cimetidine, digoxin, miconazole, morphine, nifedipine, procainamide, quinidine, quinine, ranitidine, triamterene,... 

The inherent anticholinergic properties of procainamide may interfere with the therapeutic effect of cholinergic agents. Patients receiving cimetidine and procainamide may exhibit signs of procainamide toxicity, as cimetidine inhibits the metabolism of procainamide. Simultaneous... 

Concurrent administration of propafenone with digoxin, warfarin, propranolol, or metoprolol increases the serum concentrations of the latter four drugs. Cimetidine slightly increases the propafenone serum concentrations. Additive pharmacological effects can occur when lidocaine, procainamide, and quinidine are combined with propafenone. 

Procainamide (Pronestyl, Pronestyl SR, Procanbid) [Antiarrhythmic] WARNING Only use in life-treating arrhythmias hematologic tox can be severe Uses Supraventricular/ventricular arrhythmias Action Class 1A antiarrhythmic (Table VI-7) Dose Adults. Recurrent VF/pulseless VT 20 mg/min slow IV inf to a max of 17 mg/kg or until QRS T by 50% or dysrhythmia resolves Maint inf 4 mg/min (mix 1 gm in 250 mL NS to make 4 mg/mL use 60 gtt set—60 gtt/min = 4 mg) Peds. Loading dose 15-50 mg/kg IV/IO Caution [C, +] Contra Complete heart block, 2nd- or 3rd-degree heart block w/o pacemaker, torsades de pointes, SLE Disp Tabs caps 250, 500 mg SR tabs 500, 750, 1000 mg inj 100, 500 mg/mL SE 1 BP, lupus-like synd, GI upset, taste perversion, arrhythmias, tach, heart block, angioneurotic edema, blood dyscrasias Interactions T Effects W/ acetazolamide, amiodarone, cimetidine, ranitidine, trimethoprim T effects OF anticholinergics, antihypertensives i effects W/ procaine, EtOH EMS Monitor BP and ECG use caution to prevent rapid... 

---