On-call scenario 6: Sources
These resources might be helpful:• BNF
• Martindale and/or AHFS Drug Information (if you have access)
• Micromedex or UpToDate (if you have access)
• Trip Pro Database (this is free on NHS computers and so if you are on-call at home you'll need to log-in to your work's network to access it)
• Your local Trust guidelines
You search the BNF, SmPC and NEWT guidelines, and unfortunately, they do not have information on how to switch between different desmopressin formulations. However, you find that Martindale states that ‘the intranasal dose of desmopressin is about 10 times that required intravenously, and the oral dose is about 10-20 times greater than the intranasal dose.’ It comments that there is a wide interindividual variation in the dose required to maintain adequate antidiuresis and doses should be titrated according to response when changing between formulations.
Oral desmopressin dose: 200 micrograms TDS = 600 micrograms daily.
Intranasal desmopressin dose: 30 – 60 micrograms daily as one or 2 divided doses.
IV or SC desmopressin dose: 3-6 micrograms once daily.
Intranasal desmopressin dose: 30 – 60 micrograms daily as one or 2 divided doses.
IV or SC desmopressin dose: 3-6 micrograms once daily.
Whilst working out-of-hours, you might like somebody to check these calculations for you. For example, you could give the doctor the necessary equivalence values, and see whether you come to the same answer.
Delaying or omitting doses of desmopressin in patients with diabetes insipidus may lead to severe dehydration and death. Therefore you will need to ensure that the medicines is supplied tonight. NHS England have issued a patient safety alert on the matter in 2016.