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Mental health
Fine tuning of dosages is crucial
From Mr J. A. Bland, MRPharmS
One specific area of prescribing practice on which pharmacists, as supplementary
prescribers, can have a positive impact is in relation to the fine tuning
of drug dosages for individual patients. In my experience drugs are sometimes
prescribed in block dosages and with too rapid a dose escalation.There
are probably many reasons why this occurs in relation to the prescriber,
a principal one perhaps being the “one size fits all” policy.
But as any pharmacist knows, one size never has and never will fit all
patients.
A key area of clinical practice where fine tuning and individualising
drug dosages is critical is in mental health, which the Government has
recognised with the Mental Health National Service Framework. The coarse
approach to prescribing previously mentioned can be especially damaging
to patients, particularly for drugs acting on the central nervous system.Where
doses are prescribed that are higher than clinically needed, the likelihood
of both physical and neurological side effects is increased, which, in
turn, will damage patient compliance and confidence in the system. In
addition, where the drugs involved are expensive, eg, the atypical antipsychotics,
failure in each individual case to prescribe the absolutely minimal dose
required to achieve an optimal outcome for the patient will have, and
is having, huge financial implications for primary care trusts and secondary
care.
Fine tuning, then, in my opinion, is crucial, but a practical determinant
to enable a practitioner to do this for each drug is the formulations
available. With regard to three of the most commonly used atypical antipsychotics,
namely, quetiapine, risperidone and olanzapine, the following is of note.
As a percentge of the British National Formulary maximum daily dose (mdd)
the drug that is least user-friendly as far as fine tuning is concerned
is olanzapine, where the smallest percentage increase or decrease of
the mdd that the formulations available will allow is 12.5 per cent,
whereas with quetiapine, for example, a percentage increase or decrease
of the mdd of 3.3 per cent is achievable. The reality of this as far
as olanzapine is concerned is that the smallest increase or decrease
of dose that the currently available tablet strengths will allow for
is 2.5mg.
Given the fact that the mental health trust for which my trust provides
clinical services considers the 100mg chlorpromazine equivalent of olanzapine
to be 3mg, then 2.5mg of olanzapine would therefore have an approximate
chlorpromazine equivalent value of 83mg. This, I propose, is far too
crude an amount to allow for fine dose titration.
Jonathan Bland
Newark,
Nottinghamshire
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