Background Although medication induced syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a common clinical entity, several issues remain unaddressed in the current literature. As most of the available data are derived from case reports and small case series, the distribution of the different medication classes as SIADH aetiologies is unknown. It is also not known whether different medication classes are associated with different severity and outcomes of SIADH. The percentage of patients with SIADH who take a suspected medication and are actually diagnosed with medication induced SIADH is unknown. Also, whether these patients can be differentiated by clinical parameters from those with SIADH due to other causes has not been studied.

Purpose To determine the distribution of aetiologies for medication induced SIADH in hospitalised patients, and to characterise them according to the different medication groups.

Material and methods A single centre retrospective study was conducted including all patients diagnosed with SIADH in a large community hospital and tertiary centre between 1 January 2007 and 1 January 2013 who were treated with medications known to be associated with SIADH. Two physicians reviewed every patient’s medical file for predetermined relevant clinical data.

Results The study cohort included 198 patients who had SIADH and received medications associated with SIADH. Most patients (146, 73.7%) were diagnosed with medication associated SIADH, while 52 (26.3%) were diagnosed with SIADH due to other aetiologies. The Naranjo algorithm differentiated well between the two groups (p<0.001). 5 medication classes, namely antidepressants, anticonvulsants, antipsychotics, cytotoxic agents and analgesics, were implicated in 82.3% of patients diagnosed with medication associated SIADH. Specific serotonin reuptake inhibitors and carbamazepine were commonly implicated. There were no clinically significant differences in characteristics or severity of SIADH according to medication class.

Conclusion Medication induced SIADH is mostly caused by 5 medication classes. The Naranjo algorithm successfully differentiated between medication induced SIADH and SIADH due to other aetiologies in patients treated with these medications. Clinical characteristics were comparable between SIADH caused by different medications. Physicians should be aware of the high likelihood of medication induced SIADH among patients treated with the implicated medication classes.

No conflict of interest