Final answer:
Injectable amides are preferred over esters due to their reduced risk for allergic reactions and increased stability, which is not directly linked to increased potency but does affect the overall efficacy and safety profile of the medication.
Step-by-step explanation:
Injectable amides are recommended over esters for a couple of significant reasons. Firstly, there is less risk for allergic reactions with amides than with esters. This reduced risk is due to the fact that the metabolic degradation products of amides are generally amino acids, which are less likely to cause systemic toxicity or trigger allergic reactions compared to the more complex degradation products of esters.
Additionally, amides are the least reactive among acyl substrates due to the effects of resonance stabilization, which gives the carbonyl carbon of amides lesser electrophilicity. This makes amides more stable, enhancing their safety profile. Esters, conversely, are more readily hydrolyzed, which can lead to faster degradation and potentially more variable pharmacokinetic profiles. This ability to hydrolyze quickly can also affect the potency of esters, whereas amides tend to maintain their pharmacological effects longer due to their stability.
So, when comparing the two, amides are often chosen for their safety and stability over esters.