For the metabolite, the mean plasma-elimination half-life was approximately 61 days. These data probably reflect an initial elimination of drug from well-perfused tissue the 2. The considerable intersubject variation in both phases of elimination, as well as uncertainty as to what compartment is critical to drug effect, requires attention to individual responses once arrhythmia control is achieved with loading doses because the correct maintenance dose is determined, in part, by the elimination rates.
The parent drug and its metabolite have been detected in breast milk. Although electrophysiologic effects, such as prolongation of QTc, can be seen within hours after a parenteral dose of amiodarone hydrochloride, effects on abnormal rhythms are not seen before 2 to 3 days and usually require 1 to 3 weeks, even when a loading dose is used. There may be a continued increase in effect for longer periods still. There is evidence that the time to effect is shorter when a loading-dose regimen is used.
In general, when the drug is resumed after recurrence of the arrhythmia, control is established relatively rapidly compared to the initial response, presumably because tissue stores were not wholly depleted at the time of recurrence. Within individuals dose reductions and ensuing decreased plasma concentrations can result in loss of arrhythmia control. Plasma-concentration measurements can be used to identify patients whose levels are unusually low, and who might benefit from a dose increase, or unusually high, and who might have dosage reduction in the hope of minimizing side effects.
Monitoring Effectiveness Predicting the effectiveness of any antiarrhythmic agent in long-term prevention of recurrent ventricular tachycardia and ventricular fibrillation is difficult and controversial, with highly qualified investigators recommending use of ambulatory monitoring, programmed electrical stimulation with various stimulation regimens, or a combination of these, to assess response.
There is no present consensus on many aspects of how best to assess effectiveness, but there is a reasonable consensus on some aspects: If a patient with a history of cardiac arrest does not manifest a hemodynamically unstable arrhythmia during electrocardiographic monitoring prior to treatment, assessment of the effectiveness of amiodarone hydrochloride requires some provocative approach, either exercise or programmed electrical stimulation PES.
Whether provocation is also needed in patients who do manifest their life-threatening arrhythmia spontaneously is not settled, but there are reasons to consider PES or other provocation in such patients. More controversial is the meaning of continued inducibility.
There has been an impression that continued inducibility in amiodarone hydrochloride patients may not foretell a poor prognosis but, in fact, many observers have found greater recurrence rates in patients who remain inducible than in those who do not. These criteria include increased difficulty of induction more stimuli or more rapid stimuli , which has been reported to predict a lower rate of recurrence, and ability to tolerate the induced ventricular tachycardia without severe symptoms, a finding that has been reported to correlate with better survival but not with lower recurrence rates.
While these criteria require confirmation and further study in general, easier inducibility or poorer tolerance of the induced arrhythmia should suggest consideration of a need to revise treatment.
As amiodarone hydrochloride has been studied principally in patients with refractory life-threatening ventricular arrhythmias, in whom drug therapy must be selected on the basis of response and cannot be assigned arbitrarily, randomized comparisons with other agents or placebo have not been possible. Overall arrhythmia-recurrence rates fatal and nonfatal also were highly variable and, as noted above, depended on response to PES and other measures , and depend on whether patients who do not seem to respond initially are included.
Recurrent hemodynamically unstable ventricular tachycardia. An alternative statin, pravastatin Pravachol , does not share this interaction and is safer in patients taking amiodarone. Amiodarone inhibits the metabolism of dextromethorphan, the cough suppressant found in most over-the-counter and some prescription cough and cold medications for example, Robitussin -DM.
Although the significance of the interaction is unknown, these two drugs probably should not be taken together if possible. Grapefruit juice may reduce the breakdown of amiodarone in the stomach leading to increased amiodarone blood levels. Grapefruit juice should be avoided during treatment with amiodarone. Is amiodarone safe to take if I'm pregnant or breastfeeding?
Amiodarone should not be used during pregnancy because it can cause fetal harm. There have been reports of congenital hypothyroidism or hyperthyroidism when amiodarone was administered during pregnancy.
Amiodarone is excreted in breast milk and may cause adverse effects in the infant. Breastfeeding should be discontinued by mothers receiving amiodarone. What else should I know about amiodarone? What preparations of amiodarone are available? Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: Get medical help right away if you have any very serious side effects, including: Amiodarone may rarely cause thyroid problems. Either low thyroid function or overactive thyroid function may occur. This drug may cause your skin to be more sensitive to the sun. With long-term treatment, you may rarely develop blue-gray color of the skin. This effect is not harmful and color may return to normal after the drug is stopped.
To help prevent skin effects, limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. This drug may rarely cause vision changes. Very rarely, cases of permanent blindness have been reported. Tell your doctor right away if you develop any vision changes such as seeing halos or blurred vision.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction , including: This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at Precautions See also Side Effects section.
Before taking amiodarone , tell your doctor or pharmacist if you are allergic to it; or to iodine; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems.
Talk to your pharmacist for more details. Before using this medication , tell your doctor or pharmacist your medical history, especially of: This drug may make you dizzy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely.
Before having surgery, tell your doctors or dentist about all the products you use including prescription drugs , nonprescription drugs, and herbal products. Amiodarone may cause a condition that affects the heart rhythm QT prolongation.
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