L ocal anesthetics are divided into 2 main groups based on their chemical structure: amides and esters. Prilocaine (Citanest®, AstraZeneca Pharmaceuticals, Wilmington, Del) is a commonly used agent in infiltrative anesthesia, and its adverse effects are well known. It has been the least toxic of the presently used agents containing an aromatic benzene ring in their molecules.^1,2
Adverse reactions from the amide group of local anesthetics are rare.³ Adverse reactions include toxic, psychosomatic, idiosyncratic, and allergic-pseudoallergic reactions. The likelihood of these reactions appears to depend on the dosage, the surface area of application, the condition of the skin, and the systemic hepatic, renal, or cardiac functions.⁴ Local reactions include the development of erythema, pallor, and edema. Amide anesthetics may also provoke other reactions, such as swelling, ulceration, nausea, and drug eruptions.³ Immunoglobulin E-mediated allergic reactions, such as urticaria, angioedema, bronchial spasm, and anaphylactic shock, are uncommon.^4,5 There is a delayed type of allergic reaction with local anesthetics characterized by swelling within 2 to 24 hours, which lasts for several days.⁴
Prilocaine is rapidly metabolized by the liver and kidneys.⁶ Allergic reactions may be caused by the anesthetic, a metabolite, a preservative, or an unrelated substance.⁴
The authors present a case of skin necrosis after the use of prilocaine as an infiltrative anesthetic, which has not been reported previously.

Case Report

A 48-year-old woman was admitted to the hospital with a trigger thumb on her left hand. She was operated under local anesthesia, containing 20mg/mL prilocaine and 1mg/mL parahydroxybenzoate. It was applied on the volar and radial aspects of her left hand to block radial and median nerves; in addition, some was injected locally. The injections were controlled by pulling back the syringe. Total dose of anesthetic was not much more than 1 flacon. The operation was comfortable. Twelve hours after the operation, the patient felt pain at the infiltration sites, and she experienced an itching at these sites 24 hours after the operation. Erythema was apparent on the volar and radial aspects of her wrist. In time, the skin became red and edematous. The hand was elevated, and systemic antibiotic therapy with ampicillin-sulbactam was initiated. After 3 days, skin necrosis was apparent (Figure 1). Wound debridement was planned. The patient was diabetic and using oral antidiabetics, and upon endocrinologic consultation, her parameters were regular. A wide debridement exposed the median nerve and the tendons and revealed full-thickness skin necrosis. A groin flap based medially on the superficial circumflex iliac artery was used to cover the defect. The postoperative course was uneventful, and a good esthetic and functional result was obtained.

Discussion

Prilocaine is an amidoamide group local anesthetic and is the least toxic agent in this group.² It is metabolized rapidly in the liver and kidneys, and its toxic effect to the cardiovascular system and central nervous system is minimal.¹ There are many adverse reactions with local anesthetics, including toxic, psychosomatic, idiosyncratic, and allergic-pseudoallergic reactions. The reported adverse effects with local anesthetics develop in less than 30 minutes in 50% of patients and more than 2 hours in the remaining half of patients.⁵ The reactions (ie, anxiety, seizures, slow speech, and tremor) are due to overdosage or abnormal absorption, resulting in central nervous system hyperactivation and cardiovascular system disorders.^4,6 The psychosomatic reactions, such as dizziness, hyperventilation with dyspnea, and bradycardia, are not drug related and include the autonomic nervous system.