Conduction disturbances

The side effects and toxic reactions to verapamil iaclude upper GI upset, constipation, di22iaess, headaches, flushing and burning, edema, hypotension, bradycardia, and various conduction disturbances. Verapamil has negative iaotropic activity and may precipitate heart failure ia patients having ventricular dysfunction (1,2). 

Verapamil (Table 1), the first slow channel calcium blocker synthesized to selectively inhibit the transmembrane influx of calcium ions into cells, lowers blood pressure in hypertensive patients having good organ perfusion particularly with increased renal blood flow. Sustained-release verapamil for once a day dosing is available for the treatment of hypertension. Constipation is a prominent side effect. Headache, dizziness, and edema are frequent and verapamil can sometimes cause AV conduction disturbances and AV block. Verapamil should not be used in combination with -adrenoceptor blockers because of the synergistic negative effects on heart rate and contractile force. 

The P-blockers propranolol and timolol are FDA-approved for migraine prophylaxis, but other drugs in the class are also as effective.46 Cautious dosage titration is advised for those patients who do not have other indications for P-blocker use. Rizatriptan interacts with propranolol and thus dosages must be titrated downward, or another triptan chosen for abortive therapy.36 Comorbid reactive airway disease is a relative contraindication to P-blocker prophylaxis, and patients with cardiac conduction disturbances should be closely monitored. Calcium channel antagonists are often used when patients cannot tolerate P-blockers. They are purported to beneficially... 

Adverse reactions CNS Convulsions, confusion, drowsiness, myoclonus, fever Dermatologic Rash Metabolic Electrolyte imbalance Hematologic Positive Coombs test, hemolytic anemia Local Rain, thrombophlebitis Renal Acute interstitial nephritis Miscellaneous Anaphylaxis, hypersensitivity, Jarisch-Herxheimer reaction CNS Seizures, confusion, drowsiness, myoclonus, CNS stimulation Cardiovascular Myocardial depression, vasodilation, conduction disturbances Hematologic Positive Coombs test, hemolytic anemia, neutropenia Local Thrombophlebitis, sterile abscess at injection site Renal Interstitial nephritis Miscellaneous Pseudoanaphylactic reactions, hypersensitivity, Jarisch-Herxheimer reaction, serum sickness... 

Quinidine Cinchonism, diarrhea, abdominal cramps, nausea, vomiting, hypotension, TdP, aggravation of underlying HF, conduction disturbances or ventricular arrhythmias, fever, hepatitis, thrombocytopenia, hemolytic anemia... 

Disopyramide Anticholinergic symptoms (dry mouth, urinary retention, constipation, blurred vision), nausea, anorexia, TdP, HF, aggravation of underlying conduction disturbances and/or ventricular arrhylhmias, hypoglycemia... 

Lidocaine Dizziness, sedation, slurred speech, blurred vision, paresthesia, muscle twitching, confusion, nausea, vomiting, seizures, psychosis, sinus arrest, aggravation of underlying conduction disturbances... 

Terminate IV therapy if persistent conduction disturbances or hypotension develop. As soon as the patient s basic cardiac rhythm appears to be stabilized, oral antiarrhythmic maintenance therapy is preferable (if indicated and possible). A period of approximately 3 to 4 hours (one half-life for renal elimination, ordinarily) should elapse after the last IV dose before administering the first dose of oral procainamide. 

Hypersensitivity to cyclobenzaprine concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation acute recovery phase of Ml and in patients with arrhythmias, heart block, or conduction disturbances or CHF hyperthyroidism. 

Conduction Disturbances During Acute Myocardial Infarction... 

Stellbrink C, Breithardt OA, Franke A, et al. Impact of cardiac resynchronization therapy using hemodynami-cally optimized pacing on left ventricular remodeling in patients with congestive heart failure and ventricular conduction disturbances, [see comment]. J. Am. Coll. Cardiol. 2001 38 1957-65. 

Tricyclic antidepressants are cardiotoxic, inducing tachycardias and an increased tendency for ventricular arrhythmias with high doses. This dose dependent cardiotoxicity gives these agents a low therapeutic index. Overdoses are characterized by cardiac conduction disturbances, hyperpyrexia, hypertension, confusion, hallucinations, seizures and coma and there is a high mortality rate in suicide attempts. Depressed patients should therefore not be given more than one week supply of these drugs. 

The major toxic reactions to disopyramide administration include hypotension, congestive heart failure, and conduction disturbances. These effects are the result of disopyramide s ability to depress myocardial contractility and myocardial conduction. Although disopyramide initially may produce ventricular tachyarrhythmias or ventricular fibrillation in some patients, the incidence of disopyramide-induced syncope in long-term therapy is not known. Most other toxic reactions (e.g., dry mouth, blurred vision, constipation) can be attributed to the anticholinergic properties of the drug. 

Although the p-blockers are well-tolerated drugs and patient compliance is good, there may be problems with their administration, particularly in patients with decompensated hearts and cardiac conductance disturbances. These potential problems and the adverse effect of p-blockers are described in detail in Chapter 11. 

Ipecac syrup is prepared from the dried rhizome and roots of Cephaelis ipecacuanha or Cephaelis acuminata, plants from Brazil and Central America that have the alkaloid emetine as their active principal ingredient. It acts directly on the CTZ and also indirectly by irritating the gastric mucosa. Ipecac is cardiotoxic if absorbed and can cause cardiac conduction disturbances, atrial fibrillation, or fatal myocarditis. If emesis does not occur, gastric lavage using a nasogastric tube must be performed. 

Other Orthostatic hypotension, cardiac conduction disturbances, anticholinergic... 

Use with caution in older patients with Parkinson s Disease (an atypical antipsychotic is recommended), seizure disorders, cardiovascular disease with conduction disturbance, hepatic encephalopathy, narrow-angleglaucoma, congenital prolonged O-T syndrome or drugs which prolong O-T interval. 

Contraindications Acuf e recovery phase of MI, arrhythmias, CHF, heart block, conduction disturbances, hyperthyroidism, use within 14 days of MAOIs... 

Overdose may increase QRS duration, prolong QT interval, cause conduction disturbances, reduce myocardial contractility, and cause hypotension. 

CNS Bowel Dysfunction Bladder Dysfunction Falls Other Orthostatic hypotension, cardiac conduction disturbances, torsades de pointes, anticholinergic side effects. 

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