Delirium with visual hallucinations induced by low‐dose olanzapine

Delirium is an acute condition characterized by impaired consciousness and attention, and accompanied by agitation and visual hallucinations, and could be caused by drugs, especially those with anticholinergic effects. Olanzapine (OLZ) is an atypical antipsychotic drug with various side-effects such as weight gain and drowsiness. Therefore, to take advantage of these effects, OLZ is occasionally used to treat decreased appetite and nausea in cancer patients. While the medication is also known to have a therapeutic effect on delirium, its anticholinergic effects have been found to actually cause or worsen delirium in rare cases. Nevertheless, there are only a small number of reports regarding OLZ-induced delirium, especially in patients that received a low dosage, with a few reports known to be presented. We report here details of a case of delirium with vivid visual hallucinations in an uncomplicated lung cancer patient, which was clearly induced by low-dose OLZ treatment. The patient was a 70-year-old Japanese female with no history of mental illness or dementia. Her activities of daily living were normal. Two months prior to hospital admittance, she was diagnosed with lung cancer, adenocarcinoma clinical stage T4N2M1. The patient was admitted for pain control related to lung cancer and bone metastasis (Day 1). On Day 2, oral administration of sustained-release oxycodone (Oxycontin) was increased from 20 to 30 mg, and oral immediaterelease oxycodone (OxyNorm) at 5 mg was added for face and lower back pain caused by bone metastasis. Oral gefitinib was also started at 250 mg oral on Day 3. Left temporal bone irradiation (30 Gy/10 fractions) was performed daily from Day 4 to 17. OLZ at 5 mg was added on Day 19 due to loss of appetite caused by mouth ulcers and pain that developed during hospitalization. The next day, she showed noticeable wobbling and fell, though she could not remember the incident. On Day 21, she stood on the bed, pointed to the curtain and said, ‘There is someone behind there. Don’t talk to him. It will be dangerous if he finds out!’, along with other statements that did not make sense. Furthermore, insomnia was also noted. Delirium Rating Scale (DRS) (Table 1) and Mini-Mental State Examination (MMSE) scores were 22 and 19, respectively. Due to suspicion of delirium, OLZ was discontinued, while suvorexant at 15 mg was added for insomnia. On Day 22, the visual hallucinations and delirium were resolved, and then on Day 26 the DRS and MMSE scores were 6 and 25, respectively (Table 1). The patient remembered approximately half of the hallucination episode and said with a laugh, ‘It was very scary when the soldiers held up their guns. It was a good experience’. Thereafter, no symptoms of delirium were observed until discharge on Day 27. We report a case of delirium caused by low-dose OLZ with vivid hallucinations. Two distinguishing points in this case were vivid and frightening hallucinations and the development of delirium consistent with the duration of OLZ use. Patients affected by such conditions as Dementia with Lewy bodies, Charles Bonnet syndrome, migraine, and psychosis sometimes experience visual hallucinations. Vivid hallucinations are known to often occur in individuals with good insight, while frightening or contentious hallucinations are often found in those with a psychotic disorder or delirium. However, delirium in combination with vivid hallucinations with frightening content is rarely encountered. One possibility for such a complex hallucination is that the multiple effects of OLZ may cause a disturbance of the limbic system neurotransmitters. The present results showing that symptoms were induced by OLZ and then improved following its discontinuation support druginduced delirium. The DRS score in our patient was reduced from 22 to 6, and a score greater than 20 points has high specificity indicating delirium. The cause of delirium in this case could also be related to brain function vulnerability, including age greater than 70 years, use of the opioid, and radiotherapy treatment of temporal bone. Delirium caused by irradiation is rare, though it