Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Nanac on 25/09/2006 07:42:02
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How chemicals specially Medicines , only few molecules expire gradually and why not all spontaneously ?
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The degredation of a medicine will normally be a chemical reaction. For the reaction to happen a variety of prerequisites will need to be fulfilled. The molecule(s) must have enough energy, the energy must be of the right form and in the right part of the molecule(s), the molecules must meet, the molecule(s) must be in the right orientation etc, etc, etc. Because only a very small proportion of the total molecules fulfill these conditions every day, only a very small proportion of them will react and become inactive every day.
Some will degrade before you have even bought the packet, and there will be a lot left un degraded at the expiry date. The expiry date will be set so that the medcine will still be behaving close enough to a new packet that you/your doctor don't have to worry.