Allergies
Although patients receiving local anesthetics may experience a
range of local and systemic symptoms, prospective studies indicate that very few
of these reactions are confirmed as allergic reactions.[183]
Aminoester drugs such as procaine may produce allergic-type reactions.[184]
These drugs are derivatives of p-aminobenzoic acid,
which is known to be allergenic. Aminoamide local anesthetics are not derivatives
of p-aminobenzoic acid, and allergic reactions to
these drugs are extremely rare. Although the aminoamide anesthetics appear to be
relatively free of allergic-type reactions, solutions of these drugs may contain
a preservative, methylparaben, whose chemical structure is similar to that of p-aminobenzoic
acid. Contamination of vials with latex antigen has been suspected in some allergic
reactions, although such contamination has been difficult to confirm.[185]
In the very rare patient for whom confirmed allergy to both aminoamides and aminoesters
precludes their use for spinal anesthesia, meperidine can be considered as an alternative.
[186]
