Amiodarone dosage

Recommendations for Oral Amiodarone Dosage After IV Infusion ... 

Depression has been attributed to amiodarone in a 65-year-old woman who was taking amiodarone (dosage not stated) (15). Because the mode of presentation was atypical in onset, course, duration, and its response to antidepressant drugs, amiodarone was withdrawn, and she improved rapidly. There was no evidence of thyroid disease. 

Poliak PT, Sharma AD, Carruthers SG. Correlation of amiodarone dosage, heart rate, QT interval and corneal microdeposits with serum amiodarone and desethylamio-darone concentrations. Am J Cardiol 1989 64(18) 1138 3. 

Information is very limited but a reduced response to amiodarone may be expected. Separating the dosages to avoid admixture in the gut would reduce or prevent any effects on absorption from the gut, but not the effects due to reduced enterohepatic recirculation. Monitor concurrent use closely and consider an alternative to colestyramine, or raise the amiodarone dosage if necessary. 

It is not clear whether or not the amiodarone dosage should be inereased to accommodate this interaction because the metabolite of amiodarone (A-desethylamiodarone) also has important antiarrhythmic effects. ... 

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. 

Amiodarone adsorbs to polyvinyl chloride (PVC) tubing, and the clinical trial dose administration schedule was designed to account for this adsorption. Clinical trials were conducted using PVC tubing therefore its use is recommended. The concentrations and rates of infusion provided in Administration and Dosage reflect doses identified in these studies. It is important that the recommended infusion regimen be followed closely. 

If a diagnosis of amiodarone-induced hypersensitivity pneumonitis is made, discontinue amiodarone and institute steroid treatment. If a diagnosis of amiodarone-induced interstitial/alveolar pneumonitis is made, institute steroid therapy and discontinue amiodarone or, at a minimum, reduce dosage. 

Tremors of the hands and sleep disturbances in the form of vivid dreams, nightmares, and insomnia have been reported in association with the use of amiodarone. Ataxia, staggering, and impaired walking have been noted. Peripheral sensory and motor neuropathy or severe proximal muscle weakness develops infrequently. Both neuropathic and myopathic changes are observed on biopsy. Neurological symptoms resolve or improve within several weeks of dosage reduction. 

The authors suggested that the development of Cushing s syndrome and its persistence at a low dosage of budesonide was caused by inhibition of the metabolism of budesonide by amiodarone. 

There has been a retrospective study of the frequency of amiodarone-associated thyroid dysfunction in adults with congenital heart disease (41). Of 92 patients who had taken amiodarone for at least 6 months (mean age 35, range 18-60 years), 36% developed thyroid dysfunction— 19 became hyperthyroid and 14 hypothyroid. The mean dosage was 194 (100-300) mg/day, and the median duration of therapy was 3 (0.5-15) years. Female sex (OR = 3) and unoperated or palliated cyanotic congenital heart disease (OR = 7) were significant susceptibility factors for thyroid dysfunction. The risk was also dose-related. Although the authors conceded that they may have over-estimated the... 

Amiodarone-induced lens opacities have also been reported. Fine anterior subscapular lens deposits occur in approximately 50% of patients taking amiodarone in moderate to high dosages (600 to 800 mg daily) after 6 to 18 months of treatment.The deposits first appear as small golden brown or white-yellow punctate opacities located just below the anterior lens capsule. Unlike the lenticular deposits associated with chlorproma2ine therapy, which develop before corneal changes, the lens opacities... 

Of 85 patients with persistent atrial fibrillation after balloon mitral valvotomy given amiodarone (600 mg/day for 2 weeks and 200 mg/day thereafter), 33 converted to sinus rhythm (29). Of the other 52 patients, who underwent DC cardioversion at 6 weeks, 41 converted to sinus rhythm. Six patients had adverse effects attributable to amiodarone. Five had mild gastrointestinal symptoms, such as abdominal discomfort and nausea. One developed hypothyroidism after 3 months, which resolved when the dosage of amiodarone was reduced to 100 mg/day. 

In a meta-analysis of 10 studies of the use of amiodarone in patients with heart failure, the overall odds ratio for mortality with amiodarone compared with placebo was 0.79 (95 % Cl = 0.68, 0.92). The corresponding odds ratio for adverse effects was 2.29 (1.97,2.66) (36). The benefit to risk ratio of the use of amiodarone in these patients is not yet clear. The dosage of amiodarone in these studies varied from 50 to 400 mg/day, with an average of around 250 mg/day. 

A 77-year-old man without a history of lung disease was given amiodarone 7 days after bypass surgery because of supraventricular dysrhythmias and non-sustained ventricular tachycardia (74). He had taken 1600 mg/ day for a week followed by a maintenance dosage of 400 mg/day, and 15 days later became pale, sweaty, febrile, and tachypneic. His blood pressure was 100/60 and his heart rate 100/minute. There were reduced breath sounds and crackles throughout the lung fields. 

Epididymitis has been reported in patients taking high dosages of amiodarone, resolving with dosage reduction or withdrawal (SEDA-18, 203). 

This case was unusual in that it involved both testes. The mechanism of this effect is not known, but it has been reported to be dose-dependent, although anti-amiodar-one antibodies have also been reported (208). The incidence is not known, but has been reported to be as high as 11%. The author of one very brief report (209) claimed to have seen 20 cases of epididjmitis, some of which were bilateral, since the late 1980s. He claimed that withdrawal produced dramatic resolution of symptoms within 10-20 days, and that amiodarone in a dose of 200 mg/day did not usually cause symptoms, even in patients who had had epididjmitis at higher dosages. 

In a study of this interaction in 43 patients who took both amiodarone and warfarin for at least 1 year, the interaction peaked at 7 weeks and the mean dosage of warfarin fell by 44% from 5.2 to 2.9 mg/day (265). The dosage of warfarin correlated inversely with the maintenance dose of... 

Amiodarone Potentiation (114-117) Reduced warfarin and acenocoumarol clearances (114,117) Adjust dosage... 

Ingestion is the most common route of both accidental and intentional exposures to amiodarone although few cases exist in the literature. Amiodarone is available in an oral dosage form and a parenteral dosage form for intravenous administration. 

The pharmacokinetics of the antiarrhythmic agents are summarized in Table 17-4, and a nomogram for estimating effective dosages of the oral forms (except amiodarone) is shown in Fig. 17-5. Dosing recommendations for the intravenous forms are shown in Table 17-5. 

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