Dilution technique

[Urukhai]

Could anyone help me out with the following question please?
Say how you prepare a 62.5mg/5ml amoxicillin solution from a 125mg/5ml amoxicillin solution.
Are there any good books that could help me to learn about extemporaneous preparation that anyone could recommend as have never had to do this sort of thing before and am trying to pick up the basics. I spent all night on the internet last night, but am having trouble finding a good site or refernce source to help me understand.
Many thanks in advance.

[johnep]

Basic arithmetic. 2 x 62.5 = 125.
therefore dilute to twice volume.
johnep

[Asterix]

you dilute it by 2ml dont you johnep

[johnep]

? I would dilute 100ml to 200ml.
In the old days, we would weigh the 125mg/ml powder contents. Take half then add water to make up 100ml volume. Or give directions and syringe to measure 2.5ml. latter is usual these days.
johnep

[Asterix]

why not 50ml to 100ml john

[Nik]

Well you'll waste 50ml of reconstituted antibiotic for a start...

To the original poster, a good text would be "Pharmaceutical compounding and dispensing". Very useful for extemp dispensing - uni lib should keep copies.

[Urukhai]

Thankyou for your help everyone.