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What is polymorphism?
Polymorphs are crystalline materials that have the same chemical composition but different crystal structures. The different crystal structures may lead to differences in the rate of absorption.
Because of the different crystal structures, the drugs have differences in physical, chemical, optical, mechanical properties such as melting point, rates of dissolution, density, hygroscopicity, compactability, stability.
The concept is well demonstrated by the different crystalline forms of carbon. Diamond, graphite, and fullerenes are all made of pure carbon, but their physical and chemical properties vary drastically.
Some compounds may have only one or two known solid forms. Others exist in twenty different forms, each having different physical and chemical properties.
SOME EXAMPLES OF DRUGS EXHIBITING POLYMORPHISM
· Steroids
· Barbiturates
· Sulfonamides
· Acetaminophen (analgesic)
· Loperamide hydrochloride (inhibits GI motility)
· Ribavirin (antiviral)
· Risperidone (atypical antipsychotic)
· Atorvastatin Ca (cholesterol lowering agent)
Stability presents a special concern, since it's easy to inadvertently generate the wrong form at any point in the development process. Because energy differences between forms are usually relatively small, form interconversion is common and can occur during routine API manufacturing operations and during drug product formulation, storage, and use. A new form appearing in drug product can cause product withdrawal.
concern – беспокойство, интерес, проблема
generate – спровоцировать
wrong – неправильный
relatively – относительно
during – в течение
routine – стандартный
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