I want to add gentamycin to the culture at a final concentration of 20ug/ml. But I do not have gentamycin powders but having 40000 units/ml solution. How could I prepare a 20ug/ml gentamycin culture with 40000 units/ml solution?
Thanks very much for your feedbacks! I have solved my problem!
1000 international units = 1mg of active gentamycin.
1000 international units = 1mg of active gentamycin.
Hence you have 40mg/mL gentamycin. Depending on your desired volume, dilute by a factor of 2000. e.g. 100uL filled to a volume of 20mL.
International units are commonly instituted for compounds that are isolated from natural sources where the true quantity of active material can vary or be unknown.
Gentamycin is one of these compounds. In particular the usual powder, gentamycin sulfate is amorphous and has multiple sulfate salts present as more than one derivative. When the exact quantities become known the mg dosages are preferred.
The powder has an activity of 690IU per mg according to the WHO pharmacopoeia. http://apps.who.int/phint/en/p/docf/
According to the US pharmacopeia which generally avoids using IU; gentamycin sulfate is 690ug of free base per mg of gentamycin sulfate.
http://www.pharmacopeia.cn/v29240/usp29nf24s0_m34850.html
It can therefore be deduced that
1000 international units = 1mg of active gentamycin.
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