Background:
Local anesthetics such as lidocaine and other sodium channel blockers are commonly used in obstetrics for laceration repair, epidurals, and spinal blocks. Although rare, the most common adverse effects from these medications result from drug toxicity or allergic reactions. Numerous studies in dentistry, dermatology, and emergency medicine have shown that a 1% diphenhydramine solution is comparable in anesthetic effects to lidocaine for minor laceration repairs, however no cases have been described in obstetrical literature. 

Case Presentation:
A 23-year-old gravida 1 with a reported history of an anaphylactic reaction to lidocaine and confirmatory allergy testing in Venezuela presented to Labor and Delivery for induction of labor. She strongly desired an epidural for pain control; however, our hospital was unable to offer a benzoic acid ester sodium channel blocker as an alternative to lidocaine. After fully discussing options, she agreed to an induction of labor with IV pain meds and potential use of 1% diphenhydramine local injection for laceration repair after delivery. She had a spontaneous vaginal delivery with a 2nd degree perineal laceration. The physician created a 1% diphenhydramine solution using 2mL of 5% diphenhydramine (50mg/mL) provided by the pharmacy combined with 8mL of normal saline. She then injected the solution into the vaginal tissue and perineal skin along the torn edges. The repair was done in the usual fashion. She declined any IV pain meds before or during the laceration repair and tolerated the procedure well. She reported satisfactory pain control with diphenhydramine.

Discussion
Lacerations are commonly encountered during vaginal deliveries, with 53-79% of women experiencing some form. Adequate analgesia is an essential repair component, whether via epidural or local anesthetic injection. Diphenhydramine is primarily an H1 receptor antagonist with sodium channel blocking properties similar to the amide and benzoic acid ester local anesthetics, thus giving comparable anesthesia. Although rare, lidocaine allergies pose a significant problem for obstetric patients requiring laceration repair following a delivery. Currently, there are no clear guidelines on how to proceed with a laceration repair for a patient with a true lidocaine allergy. Therefore, having an available alternative option for these patients is vital. 



Analgesia for obstetric lacerations in patients with known lidocaine allergy; local injection with 1% diphenhydramine.

Clinical Vignettes | Obstetrics and Gynecology

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Analgesia for obstetric lacerations in patients with known lidocaine allergy; local injection with 1% diphenhydramine.

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