Dear Gary
We too stopped measuring valproate (more than fifteen years ago) and usually
manage to reject all but a very few on patient's with epilepsy, probably
less than one a year get through. As far as psychiatry is concerned and
after much insistentce we agreed to follow the Maudsley guidelines (minimum
dose 750mg per day) and expect the Doc's to do the same. These are sent
away. One of our psychiatrists sent me a paper "Prescribing and monitoring
of carbamazepine and valproate - a case note review". Psychiatric Bulletin;
2000, 24, 174 -177. I still have to be convinced. The target range 50 -
100mg/L is the one they took from use in epilepsy, as far as I know there
has not been one established objectively (with evidence)! Some prescribing
practises appear strange.
As far as the previous use with epilepsy, our neurlogists used to find
patients with levels below 50mg/L that had fits well controlled and many
with levels >100mg/L that never suffered from any toxic symptoms.
Paul Robinson
Royal Berkshire Hospital
-----Original Message-----
From: Firth, Gary
To: [log in to unmask]
Sent: 04/09/2003 10:31
Subject: FW: Valproate Levels
In common with many laboratories we stopped routinely quantitating
valproate levels several years ago. We will on occasion send a sample
away for analysis when the clinician can make a good case for assessing
compliance.
However our Psychiatrists are now making a case for quantitation of
valproate in patients with bipolar disorders or when they suspect drug
interactions (extract below).
I believe that this subject was touched upon some time ago, but I would
be interested to hear what the current view is on measurement of
valproate in these circumstances.
Gary Firth
Princess Royal Hospital
Sussex
UK
'I wonder if you could clarify for me the situation regarding TDM of
sodium valproate?
Psychiatry SHOs have told me that they have been unable to obtain plasma
levels
from the lab, under the normal request system.
I realise that sodium valproate levels may be of questionable use when
carried out on a routine
basis. However, the reasons why a requests have been made probably
included:
* To test patient compliance.
* To investigate why we have not acheived clinical response in
mania/ bipolar disorder when a maximum dose has been prescribed.
* To investigate possible valproate toxicity at an apparently low
dose (may involve drug interactions?)
* Elucidating the effect of drug interactions involving valproate-
particularly invloving addition of new drugs to the regime.
Notably, the Maudsley Prescribing Guidelines 2003 includes a target
range of 50-100mg/l for bipolar disorder
and states that this 'target range is a useful guide in the absence of
clinical indicators'. Thus, psychiatrists
following this eminent guidance will be asking for levels!
Clinical Pharmacist for Mental Health'
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