There is some evidence of ferropenia correlating with neuroleptic malignant syndrome and catatonic symptoms. The aim of this prospective and naturalistic study was to investigate the implications of ferremia in patients undergoing an intramuscular injection treatment of Zuclopenthixol-acetate in Visceolo. We recruited 59 catatonic patients (33 females). Age, sex, psychiatric and somatic diagnoses, body mass index (BMI), dosage and duration of Zuclopenthixol-acetate medication and the timing of the changeover from intramuscular to oral prescription, the single dosage of Clopenthixol if initially coadministered, incidence, onset and duration of transient benign hyperthermia, iron, ferritin, transferrin and saturation values, and white and red blood cell counts as well as liver function and electrolytes were registered. A transient and benign hyperthermic reaction (mean degrees: 37.5 + 0.3 °C) lasting for an average of 3.0 + 1.9 d was shown by 72.9% patients (N = 43, 22 females), during a mean treatment period of 5.8 + 3.1 d. These patients were medicated with significant different mean doses of Zuclopenthixol-acetate and compared to the patients with normal body temperature (ANOVA P < 0.01). The duration of Zuclopenthixol-acetate application did not vary between these patients groups. Furthermore, significant differences of iron (59.5 + 30.6 μmol/dl vs. 87.8 + 40.8 μmol/dl; ANOVA P < 0.006) and transferrin saturation values (18.3 + 10.4% vs. 27.2 + 17.0%; ANOVA P < 0.02) were found. Ferritin and transferrin were not implicated in the episode of hyperthermia. Diagnoses, sex, white and red blood cell counts also did not vary between these groups. Our findings indicate a possible involvement of ferropenia in catatonic patients, regardless of the diagnoses, and in the development of benign transient hyperthermia, also known as drug fever.