Anaphylactic shock due to mefenamic acid

Mefenamic acid is a member of the fenamate class (anthranilic acid derivatives) of nonsteroidal anti-inflammatory drugs (NSAIDs). It is widely and indiscriminately used in pediatric patients against standard guidelines. The authors report a rare case of anaphylactic shock induced by mefenamic acid in an 8-year-old girl. This patient, without any significant medical history, was prescribed mefenamic acid for the management of abdominal pain by a local physician. Within 30 min of ingestion of the dose, she developed symptoms of skin rash with intense itching and perioral swelling. The patient was treated with some oral medications. However, after some time, the patient developed difficulty in breathing. At presentation to the emergency room, she was having severe respiratory distress and hypotension. With associated skin rash and history and clinical findings, the child was clinically diagnosed as suffering from anaphylactic shock. The patient was immediately treated as per standard guidelines. Clinical examination did not reveal any lymphadenopathy. It was not associated with leukocytosis and eosinophilia. The child responded well, and the shock resolved. The patient recovered completely over the next 2 days. A detailed history and evaluation were conducted. The patient had consumed only mefenamic acid in a therapeutic dose before the onset of the illness. There was no exposure to any other medications or herbal products. Mefenamic acid inhibits the cyclooxygenase (COX-1 and COX-2) and blocks the production of intracellular prostaglandins, which have a role in the inflammatory pathway. It is absorbed from the gastrointestinal tract, and peak concentration occurs approximately 2 h after ingestion. Commonly reported adverse effects are nausea, vomiting, and gastrointestinal discomfort. Gastrointestinal bleeding, ulceration, and cardiovascular events are serious adverse reactions reported. Although allergic reactions can occur, anaphylaxis is rare. The probability of these unfavorable events is higher in individuals predisposed to hypersensitivity.[1-3] As defined by the World Health Organization, hypersensitivity reactions to nonsteroidal anti-inflammatory drugs fulfill the criteria of type B adverse drug reaction (unpredictable and occurring in susceptible persons). These drugs may induce both immediate and delayed hypersensitivity reactions with a varying spectrum of severity. Different classifications and mechanisms have been proposed by Kowalski et al.[4,5] According to the standardized World Health Organization-Uppsala Monitoring Centre system for evaluating the likelihood of an adverse event and case causality assessment, our case was in the probable/likely category. No provocative tests or immunological tests could be performed. The parents were explained the potential risks associated with subsequent exposure to the drug. In the context of pediatric patients, the presentation of drug-induced anaphylaxis can be particularly concerning due to the potential for rapid deterioration. Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome, a severe and potentially fatal allergic reaction, has been reported in around 10% of patients who receive mefenamic acid. It usually develops 2–6 weeks after the initiation of treatment. Rutuja et al. have highlighted the importance and need for regulatory mechanisms for the sale of over-the-counter medications.[1] The use of this medication without medical advice is rampant, unregulated, and unmonitored. Even in patients with no known history of drug allergy, healthcare providers should maintain a high index of caution when prescribing nonsteroidal anti-inflammatory drugs to children and also educate parents on recognizing and responding to features of allergic reactions. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.