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Why are most drugs weak acids or weak bases?
Most drugs are weak acids or bases that are present in solution as both the ionized and unionized forms. Ionized molecules are usually unable to penetrate lipid cell membranes because they are hydrophilic and poorly lipid soluble. Unionized molecules are usually lipid soluble and can diffuse across cell membranes.
Why drugs are weak acids or bases?
Most drugs are salts of either weak acids or weak bases. They are absorbed in the undissociated, lipid soluble, form. The dissociation of weak acids is suppressed by low (acid) pH. Thus, theoretically, one would expect a weak acid to be absorbed, primarily in the stomach which has a low pH.
Are drugs weak bases?
The majority of drugs are weak organic acids or bases. For example, barbiturates are weak acids, whereas amphetamines and opiates are weak bases.
Are drugs acidic or basic?
Most drugs are weak organic acids or bases, existing in un-ionized and ionized forms in an aqueous environment. The un-ionized form is usually lipid soluble (lipophilic) and diffuses readily across cell membranes.
How do you tell if a drug is a weak acid or base?
The only sure way to know whether a drug is acidic or basic is to learn the functional groups that confer acidity and basicity on a molecule. This should be done even if it means learning the names of the functional groups the way you learned multiplication tables at primary school.
What is a weak acid and a weak base?
A weak acid is one that does not dissociate completely in solution while a weak base is a chemical base that does not ionize fully in an aqueous solution. Therefore, the concentration of H+ ions in a weak acid solution is always less than the concentration of the undissociated species, HA.
Is paracetamol a weak acid or base?
Paracetamol (acetaminophen) is a weak acid. Paracetamol (acetaminophen) is a white solid with a melting point of 170oC which is slightly soluble in water. Paracetamol (acetaminophen) undergoes hydrolysis in acidic conditions to produce an amine and a carboxylic acid.
Are most drugs weak acids or bases?
Uncharged drugs are more lipid soluble than charged drugs. In addition, most drugs are weak acids or weak bases. For a weak acid, when the pH is less than the pK, the protonated form (nonionized) predominates. When the pH is greater than the pK, the unprotonated (ionized) form predominates.
How do you know if a drug is a weak acid or base?
Where are weak bases absorbed?
Practically speaking, this means that if taken orally, a drug that is a weak acid will be absorbed primarily in the acidic environment; whereas, a drug that is a weak base will be absorbed in the alkaline environment small intestines.
Which is a weak acid?
A weak acid is one which doesn’t ionize fully when it is dissolved in water. Ethanoic acid is a typical weak acid. It reacts with water to produce hydroxonium ions and ethanoate ions, but the back reaction is more successful than the forward one.