Flecainide dosing

Once the arrhythmia is controlled, it may be possible to reduce the dose, as necessary, to minimize side effects or effects on conduction. PSVT and PAF The recommended starting dose is 50 mg every 12 hours. Doses may be increased in increments of 50 mg twice daily every 4 days until efficacy is achieved. For PAF patients, a substantial increase in efficacy without a substantial increase in discontinuation for adverse experiences may be achieved by increasing the flecainide dose from 50 to 100 mg twice/day. The maximum recommended dose for patients with paroxysmal supraventricular arrhythmias is 300 mg/day. 

Administration with amiodarone When flecainide is given in the presence of amiodarone, reduce the usual flecainide dose by 50% and monitor the patient closely for adverse effects. Plasma level monitoring is strongly recommended to guide dosage with such combination therapy. 

Elecainide is weU absorbed and 90% of the po dose is bioavailable. Binding to plasma protein is only 40% and peak plasma concentrations are attained in about 1—6 h. Three to five days may be requited to attain steady-state plasma concentrations when multiple doses are used. Therapeutic plasma concentrations are 0.2—1.0 lg/mL. Elecainide has an elimination half-life of 12—27 h, allowing twice a day dosing. The plasma half-life is increased in patients with renal failure or low cardiac outputs. About 70% of the flecainide in plasma is metabolized by the Hver to two principal metaboUtes. The antiarrhythmic potency of the meta-O-dealkylated metaboUte and the meta-O-dealkylated lactam, relative to that of flecainide is 50 and 10%, respectively. The plasma concentrations of the two metaboUtes relative to that of flecainide are 3—25%. Elecainide is mainly excreted by the kidneys, 30% unchanged, the rest as metaboUtes or conjugates about 5% is excreted in the feces (1,2). 

Ventricular fibrillation should be terminated by electrical defibrillation. Alternatively, lidocaine can be injected intravenously. In cases with lower frequency, ventricular tachyarrhythmia class I diugs such as aj marine, flecainide or propafenone are more effective as a result of the use-dependence of lidocaine. For prophylaxis treatment, amiodarone or sotalol may be helpful or the implantation of a cardioverter-defibrillator system. Acute amiodarone (i.v. in higher doses) can also terminate ventricular tachyarrhythmias. This action, however, seems to be mediated by its INa-blocking side effects and not (or less) by its class III like effects. 

Absorption/Distribution - Oral absorption is nearly complete. Peak plasma levels are attained at approximately 3 hours. The plasma half-life ranges from 12 to 27 hours after multiple oral doses. Steady-state levels are approached in 3 to 5 days once at steady-state, no accumulation occurs during chronic therapy. Plasma levels are approximately proportional to dose. In patients with congestive heart failure (CHF NYHA class III), the rate of flecainide elimination from plasma is moderately slower than for healthy subjects. Plasma protein binding is about 40% and is independent of plasma drug level over the range of 0.015 to about 3.4 mcg/mL. 

Cardiac conduction Flecainide slows cardiac conduction in most patients to produce dose-related increases in PR, QRS, and QT intervals. The degree of lengthening of PR and QRS intervals does not predict either efficacy or the development of cardiac adverse effects. Patients may develop new first-degree AV heart block. Use caution and consider dose reductions. The JT interval (QT minus QRS) only widens approximately 4% on the average. Rare cases of torsade de pointes-type arrhythmias have occurred. 

WARNING Co administration w/ ritonavir assoc w/ Hep hepatic decomp w/ fatalities. D/C w/ S/Sxs of H Uses HIV 1 Infxn w/ highly Tx-experienced pts or HIV 1 strains resistant to multiple protease inhibitors. Must be used w/ ritonavir 200 mg Action Antiretroviral HIV-1 protease inhibitor Dose 500 mg PO bid w/ food, administer w/ ritonavir 200 mg PO bid Caution [C, -] Sulfa aU gy, Uvct Dz Contra Mod-severe hepatic insuff concomitant use w/ amiodarone, astemizole, bepridil, cisapride, ergots, flecainide, lovastatin, midazolam, pimozide, propafenone, quinidine, rifampin, simvastatin, terfenadine, triazolam, St. John s wort Disp Caps SE HA, GI distress, rash, fati e, fat redistribution, hyperglycemia, Hep, liver Dz, lipid elevations Interactions T Effects OF anticoagulants, antipits, azole antifun-... 

Flecainide is very effective in suppressing premature ventricular contractions. However, it may cause severe exacerbation of arrhythmia even when normal doses are administered to patients with preexisting ventricular tachyarrhythmias and those with a previous myocardial... 

Propafenone has some structural similarities to propranolol and possesses weak 3-blocking activity. Its spectrum of action is very similar to that of quinidine, but it does not prolong the action potential. Its sodium channel-blocking kinetics are similar to that of flecainide. Propafenone is metabolized in the liver, with an average half-life of 5-7 hours. The usual daily dosage of propafenone is 450-900 mg in three divided doses. The drug is used primarily for supraventricular arrhythmias. The most common adverse effects are a metallic taste and constipation arrhythmia exacerbation can also occur. 

Lopinavir/Ritonavir (Kaletra) [Anrirelroviral/Protease Inhibitor] Uses HIV Infxn Action Protease inhibitor Dose Adults. Tx naive 2 tab PO daily or 1 tab PO bid Tx experiencedpt 1 tab PO bid (T dose if w/ amprenavir, efavirenz, fosamprenavir, nelfinavir, nevirapine) Peds. 7-15 kg 12/3 mg/kg PO bid 15-40 kg 10/2.5 mg/kg PO bid >40 kg Adult dose w/ food Caution [C, /-] Numerous interactions Contra w/drugs dependent on CYP3A/CYP2D6 (Table VI-8) Disp Tab, soln SE Avoid disulfiram (soln has EtOH), metronidazole GI upset, asthenia, T cholesterol/triglycerides, pancreatitis protease metabolic synd Interactions T Effects Wl clarithromycin, erythromycin T effects OF amiodarone, amprenavir, azole andfungals, bepridil, cisapride, cyclosporine, CCBs, ergot alkaloids, flecainide, flurazepam, HMG-CoA reductase inhibitors, indinavir, lidocaine, meperidine, midazolam, pimozide, propafenone, propoxyphene, quinidine, rifabutin, saquinavir, sildenafil, tacrolimus, terfenadine, triazolam, zolpidem 1 effects Wl barbiturates, carbamazepine, dexamethasone, didanosine, efavirenz, nevirapine, phenytoin, rifabutin, rifampin, St. John s wort 1 effects OF OCPs, warfarin EMS Use andarrhythmics and benzodiazepines... 

T effects OF amiodarone, astemizole, atorvastadn, barbiturates, bepridil, bupropion, cerivastatin, cisapride, clorazepate, clozapine, clarithromycin, desipramine, diazepam, encainide, ergot alkaloids, estazolam, flecainide, flurazepam, indinavir, ketoconazole, lovastatin, meperidine, midazolam, nelfinavir, phenytoin, pimozide, piroxicam, propafenone, propoxyphene, quinidine, rifabutin, saquinavir, sildenafil, simvastatin, SSRIs, TCAs, terfenadine, triazolam, troleandomycin, zolpidem X effects W/ barbiturates, carbamazepine, phenytoin, rifabutin, rifampin, St. John s wort, tobacco X effects OF didanosine, hypnotics, methadone, OCPs, sedatives, theophylline, warfarin EMS T Effects of amiodarone, diazepam, midazolam and BBs, may need X- doses concurrent use of Viagra-type drugs can lead to hypotension X- effects of warfarin concurrent EtOH use can T adverse effects T glucose ODs May cause an extension of adverse SEs symptomatic and supportive Rivasrigmine (Exelon) [Cholinesterase Inhibitor/Anri ... 

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