EVALUATION OF ORAL AND TOPICAL MINOXIDIL EXPOSURES REPORTED TO US POISON CENTERS FROM 1985-1991 - A REPORT FROM THE AMERICAN ASSOCIATION POISON CONTROL CENTERS

Minoxidil overdose occurs infrequently and little toxicity data are av ailable. This study examines the epidemiology and clinical toxicity of minoxidil exposures to both tablets and topical solutions. All cases reported to the American Association of Poison Control Centers (AAPCC) Data Collection System from 1985 to 1991 were reviewed with respect t o patient age, reason for and route of exposure, dosage form, co-inges tion, healthcare facility (HCF) referral/admission, treatment and medi cal outcome. 285 cases were reviewed. 145 (51%) occurred in children l ess than 6 years of age. 273 (96%) exposures were acute, 239 (84%) wer e accidental, 224 (79%) occurred via ingestion and 61 (21%) involved c o-ingestion. 130 (46%) patients were referred to an HCF and 32 (11%) w ere admitted. The outcomes were: minor/no effect 59%, moderate 4.2%, m ajor 1.8%, and 1 death. All topical exposures resulted in minor to no effects. Of 224 ingestions, 16 (7.1%) developed significant toxicity d efined as moderate/major effects [AAPCC criteria] or death (one case i nvolving tablets). In these 16 cases, 69% were intentional and 13 (81% ) involved co-ingestion; the most frequent effects were hypotension (6 9%), tachycardia (38%) and lethargy (31%); 44% received intravenous fl uids and vasopressors. Only 2 cases of hypotension were attributable t o minoxidil alone (no history of co-ingested drugs); both responded to intravenous fluids and dopamine. The only death was a suicide, with c o-ingestion of hydralazine, prazosin and paracetamol; terminal symptom s were intractable hypotension, coma and pulmonary oedema. It is concl uded that significant toxicity after minoxidil exposure, regardless of formulation, is associated with oral administration, intentional expo sure and co-ingestion of other agents.