STEVENS–JOHNSON SYNDROME–TOXIC EPIDERMAL NECROLYSIS OVERLAP SUSPECTED TO BE INDUCED BY A POLYPHARMACY COMPOUNDED PREPARATION FOR TRIGEMINAL NEURALGIA - THE CHALLENGE OF DRUG CAUSALITY ASSESSMENT: A CASE REPORT

Background. Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe mucocutaneous reactions that are predominantly drug-induced. Identification of the culprit drug becomes difficult when a patient receives compounded preparations containing multiple active ingredients at once, a practice still encountered in primary care. Case. A 62-year-old woman presented with a generalized eruption of dusky red macules that progressed to flaccid bullae and erosions within hours, accompanied by mucosal involvement with a positive Nikolsky sign. An epidermal detachment of 23.5% placed this case in the SJS–TEN overlap category. During the preceding 30 days, the patient had received seven prescriptions of compounded preparations for trigeminal neuralgia, with a composition that changed at almost every visit, including carbamazepine, three non-steroidal anti-inflammatory drugs, paracetamol, triamcinolone, gabapentin, and diazepam. SCORTEN on admission was 2, with a predicted mortality of 12.1%. ALDEN causality assessment of all active ingredients yielded two drugs with an identical score of 5, i.e., the probable category, namely carbamazepine and meloxicam; therefore, a single culprit could not be established. Management and outcome. All suspected drugs were discontinued, and the patient received intravenous methylprednisolone, wound care with 0.9% NaCl compresses and topical antibiotics, as well as mucosal care. Lesion progression ceased within 24 hours of drug withdrawal, re-epithelialization began on day 7, and the patient was discharged on hospital day 11 with lesions that had partly evolved into post-inflammatory hypopigmented and hyperpigmented macules. Conclusion. Prescribing multi-ingredient compounded preparations increases the risk of severe drug reactions while permanently obscuring identification of the culprit, because drug provocation testing is contraindicated. Structured causality assessment and visit-by-visit documentation of exposure are minimum requirements before a drug is declared the culprit and recorded as a lifelong contraindication for the patient.