INDICES> unstability of cotrimoxazole suspension (2)

[David Woods <david.woods@stonebow.otago.ac.nz>]

INDICES> unstability of cotrimoxazole suspension (2)
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Dear Peter,

>We are procuring and distributing large amounts of
>medicine every time. It has happened several times that some batches of
>Cotrimoxazole suspension will loose its stability.
>This will be shown by change of colour of the product while still 
>within the stated shelf time.
>Before I certained that might be because of storage conditions but their
is no
>strict control of storage condition far from temperature and light.
>Can any one tell me what might be the cause of these?

I suspect that this is an exposure to light problem. Co-trimoxazole
suspension should be protected from light if possible.
Trimethoprim powder is variable in colour. The AHFS describes it as a white
to cream coloured powder.
I can't be certain, but perhaps the colour change is due to the
trimethoprim undergoing a slight change which could be accelerated by light
and high temperature exposure. Perhaps you could make up a small batch and
store under different consditions to see if this is the problem.
Of course the best option would be to arrange assay if that is possible.
Let me know if I can be of further help.

Regards,

David Woods

Lecturer/Drug Information Consultant,
School of Pharmacy
University of Otago
PO Box 913
DUNEDIN
NEW ZEALAND
00 64 3 479 7034 (fax)
00 64 3 479 5052 (phone)
025 271 7720 (mobile)
david.woods@stonebow.otago.ac.nz

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[thanks, David! WB]
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