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Saturday, May 18, 2013
Pharmacy and Medications
Difference between S-Amlodipine and Amlodipin
My brother was on Amlodipine-10 mg developed pedal edema was switched over to S-Amlodipine 5 mg yet his leg-swelling did not vanish. When both the drugs withdrawn,leg swelling completely disappeared. Is there any essential distinction between two as far as its side effect of edema is concerned ? I got information from several responses to questions related to Amlodipine I am encouraged to ask this question because we are fed up with the leg swelling of my brother. Please help. Currently my brother is on Nebivolol 5 mg and Losartan 100.
In common with many complex molecules, amlodipine can exist in two configurations that are mirror images. A way to visualize this concept is to consider the hands. The right and left hands are clearly very similar, but they are basically mirror images of each other. Drug molecules that are mirror images of each other commonly have different activities because they fit differently into the spot where they have their activity. To extend the metaphor, the right hand would not fit comfortably into a glove made for the left hand.
Drug molecules that are mirror images or enantiomers may be designated in several ways, including using an "S" or an "R" preceding the main drug name. Normally amlodipine is an equal mix of the both mirror images (R and S forms). It turns out that the "S" form of amlodipine is the therapeutically active component, while the "R" form is essentially inactive.
Amlodipine works almost entirely by dilating the blood vessels. A problem common to medicines that work in this way is that the body attempts to compensate for their therapeutic action by retaining sodium and water, which can lead to edema. This is why amlodipine and other vasodilators are often taken with diuretics or water pills. The incidence of edema between the two medicines is likely to be similar.
The hope for using the therapeutically active form of a medicine alone as opposed to a mixture of its active and inactive forms is that removal of the therapeutically inactive component may reduce the incidence of side effects. Since the edema that occurs with amlodipine is due the body's response to the therapeutic action of S-amlodipine, using the "S" isomer alone is unlikely to reduce in the incidence of edema.
Robert James Goetz, PharmD, DABAT
Assistant Professor of Pharmacy Practice
College of Medicine
University of Cincinnati