Glucagon is relatively insoluble in water under normal physiological conditions. However, its solubility is pH-dependent.
Here's a more detailed explanation:
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Low Solubility in Neutral pH: Glucagon's structure makes it poorly soluble in water at a neutral pH (around pH 7), which is typical for bodily fluids.
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Solubility at Extreme pH Values: Glucagon becomes soluble at pH values less than 3 or greater than 9.5. This means it can dissolve in strongly acidic or alkaline solutions.
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Pharmaceutical Formulations: Despite its low solubility, glucagon is available as an injectable medication. This is achieved by providing it as a lyophilized (freeze-dried) powder, often with lactose, that is reconstituted with a sterile diluent immediately before use.
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Practical Implications: Because of its poor water solubility at physiological pH, glucagon isn't readily absorbed if taken orally. This is why it's administered intravenously, intramuscularly, or subcutaneously.
In summary, while glucagon is not readily soluble in water under normal physiological conditions, its solubility is enhanced in highly acidic or alkaline environments. Pharmaceutical formulations overcome this limitation by providing it as a reconstitutable powder for injection.
