ABSTRACT
Background: Central diabetes insipidus (CDI) is characterised by a central deficiency of arginine vasopressin (AVP) with polyuria and polydipsia. The etiology is heterogeneous. The treatment of choice is the oral or nasal application of DDAVP (synthetic analogue of AVP). CDI in the context of coronavirus disease 2019 (COVID19) has been reported in an individual case. Case Report: We present a 9-year old male with CDI of uncertain etiology. The reason for presentation was polydipsia (5 liters/ day) and polyuria/ nocturia. MRI showed a nodular thickening of the pituitary stalk and lack of T1w hyperintensity of the neurohypophysis. As expected, the level of CT-proAVP (copeptin) in serum was very low (< 2.7 pmol/litre) despite increased osmolality in serum of 306 mosm/kg. Sodium in serum was high with a maximum of 151 mmol/l. Laboratory analysis showed no involvement of other pituitary axis. Therapy was initiated with DDAVP at 1.2 mug in the morning and 0.6 mug in the evening (nasally). Treatment showed normalisation of polyuria, polydipsia, serum sodium levels and drinking quantity (2 liters/ day). The most recent dose was 6 mug in the morning and 1.8 mug in the evening. One year later the patient complained of sore throat. The pain was gone the following morning. A PCR test was positive for SARS-CoV-2. Surprisingly, with the onset of the sore throat, the half-life of the usual dosage of DDAVP therapy was significantly prolonged. Thus, the boy received the usual 1.8 mug of desmopressin in the evening (day of onset of symptoms). The effect lasted for 17 hours. Thus, the duration of action was prolonged by approximately 6 hours. The morning dose was skipped. The evening dose of 1.8 mug was then administered again at 1 p.m. at noon. This lasted for 18 hours. Thus, the duration of action was prolonged again by approximately 5 hours. After three days, the regular dosage and timing could be reintroduced. Furthermore, there was no adjustment of the dosage and no change of the manufacturer, pharmacy, application or storage of the preparation in the temporal context. Conclusion(s): In the context of a clinically mild infection with SARS-CoV-2, the half-life of DDAVP was significantly prolonged with the onset of clinical symptoms. Our case report is of clinical relevance, as even mild COVID19 may lead to a change in DDAVP pharmacokinetics. This knowledge may reduce the risk of dilutional hyponatremia.