Muddled and falling — could her tablets be lowering her sodium?
An SSRI makes the body hold on to water; a thiazide-like diuretic loses sodium. In an older person, together they can drop the sodium fast.
Select any card for the reasoning, what to watch for and an exam tip.
The puzzle
An 84-year-old woman has taken indapamide for blood pressure for years. Her GP starts citalopram for depression. Three weeks later she is muddled and unsteady and has fallen twice. Her sodium is 121.
The answer, step by step
Who is most at risk
- Older people.
- Anyone on a thiazide or thiazide-like diuretic who starts an SSRI, or the other way round.
- A low sodium already: the STOPP criteria flag both drugs if it is below 130.
- Other drugs that lower sodium, such as tramadol.
What to do
Key takeaway
SSRIs and thiazide-like diuretics each cause hyponatraemia, and older people are most at risk. Think of it in anyone on an antidepressant who becomes drowsy or confused, or falls, and check the sodium.