Salt tab for tegretol induced SIADH

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Tripolar

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Was hoping to pick the brains of my fellow psychiatrists. I have a patient who has been on tegretol for 3 months and her sodium dropped from 138 before treatment to 132 over the past 3 checks (every 3 weeks). She had problems with lithium and depakote so non-options. She is on an atypical but historically it does not seem to hold her alone. She is relatively new to me. She is doing great in terms of symptom control with the tegretol but its purely the salt.

She is a more moderate functioning person cognitively so having her do a complicated water restriction is not going to work. The last thought before bailing on it if sodium dips any lower is to do a daily salt tab. In most I would just have them salt food but again she has an RN come to give her meds twice a day and is not reliable enough to do it on her own so the RN could give the tab.

I am ok starting democycline too but would rather not complicae things. Anyone done well with simply adding some salt into the diet?

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firstly a sodium of 132 is practically normal. if it has been 132 for 9 weeks it really doesn't matter, continue to monitor, make sure she doesn't have any symptoms (and if it's chronic then likely won't) don't worry about fluid restriction. since the actual total sodium is often normal or minimally reduced in SIADH it makes no sense to add salt (water retention is the main reason for the low Na). I have only done this once where fluid restrictions failed and it just doesn't make any sense.

So what if her Na is 132? treat the patient not the numbers.

Also bear in mind than many of our patients are not actually drinking enough to warrant a fluid restriction. for something as borderline as 132, 1000-1500 fluid restriction might be done IF the pt was symptomatic (sounds like there is no symptoms from what you described). Most people actually aren't even drinking that much fluid.

This patient doesn't need demeclocycline. The other agent for SIADH is tolvaptan, a vasopressin antagonist. Incidentally lithium call also be used and works in a similar way to demeclocycline, inducing a nephrogenic diabetes insipidus by blocking the effects of vasopressin at the collecting duct and distal convoluted tubules. None of these is indicated in the patient.

Chronic symptomatic hyponatremia (particularly with confusion) or a rapid decline in Na is when rx is needed. Pts often tolerate chronic hyponatremia remarkably well (I have had pts with Na 125 persistently without any symptoms when normally we would worry about that).

132 is practically normal so I would not bother investigating further, but if you have nothing else to do you can check TSH, 0900 cortisol, urinary sodium, CXR, for completion as though carbamazepine is the likely suspect you never know!
 
The other thing is what is the pt's fluid status - SIADH should only be dx if the pt is euvolemic with normal TSH and cortisol.
 
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The other thing is what is the pt's fluid status - SIADH should only be dx if the pt is euvolemic with normal TSH and cortisol.

Not really. When someones sodium consistently drops after starting tegretol or trileptal, which is a really common occurence, there is not need to go searching for other causes. SIADH is simply the "mechanism" of how tegretol causes the hyponatremia.

Anyway, Its not the number, but rather the consistent drop over a few months. As I said if it dropped below 130 than a steady decline is not a good thing. When you are dealing with a bipolar patient with moderate cognitive functioning, assessing subtle mental status changes is difficult, atleast in this particular patient as she has a horrible memory, concentration and cognition as it is.

Thanks for the replies anyway
 
I agree, this does not need a thorough workup. SIADH until proven otherwise.

The best way to treat SIADH is fluid restriction. If you cant fluid restrict her for some reason, then salt tabs is a good alternative.
 
Is lamictal or topamax an option?
 
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