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Dear All
Can any one explain that how is it the way to calculate the amount of
active ingredient in a topical dosage from like an ointment or cream?
and indeed are there any mathematical procedure to reaching it?
thank you in advance
S Bohlooli
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The following message was posted to: PharmPK
You should design your own method of calculating the amount of active
ingredient. do enough litreature search on the ointment/cream you are
making (Books journals pharmacopeia)
Where you are stuck with arithmetic consult the nearest expert in
Pharmaceutical analysis
s.o.o
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Except I didn't get your qustion well. Usually, creams or ointments
indicate the strength of the active ingredient for example, if the
label of the cream says ingredient x is 1%w/w. This simply means that
in any 100g of the cream/ointment, you have 1g of that active
ingredient. If you take 1g of such cream/ointment, then the amount of
active ingredient will be one hundreth of a gram.
I hope this will be useful.
Titilayo
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Dear Titilayo Fakeye
thank you for your comment, but I mean that what is the rule for
considering a cream 1%, for example: betamethasone has a 0.2% topical
cream why it is not 10%? is there a mathemathical explanation for it,
could somebody reach this amount of active ingredient in a topical
dosage form mathematically using plasma concentration following oral
administration?
thanks
s bohlooli
Sincerely Yours
Sincerely Yours,
Dr Shahab Bohlooli
PharmD,PhD.
Physiology & phar macology Dept.
Faculty of Medicine
Ardabil University of Medical Sciences
Daneshkah St,
Ardabil 56197,Iran.
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Shabab,
I'll take a stab at that. Bear in mind, that it is somewhat
difficult to follow your question.
First, topical betamethasone is not formulated to provide plasma
levels, but rather to produce an effect locally (i.e., at the site of
administration). Thus, the strength of the formulation is that which
produces the desired effect. Mathematically, can one model (i.e.,
predict or simulate) the amount of active ingredient at the
administration site, and/or the strength of a formulation, to produce
a desired effect at the site of administration. This type of dose-
formulation variable-effect model sounds feasible with the
appropriate experiments, and a literature review may reveal work in
that area.
Hope that helps
Shawn Spencer, Ph.D, R.Ph.
Assistant Professor of Pharmacokinetics and Biopharmaceutics
Basic Pharmaceutical Sciences
Florida A&M University
Dyson Pharmacy Bldg. Rm. 227
Tallahassee, FL 32307
Phone: 850-599-3511
Fax: 850-599-3934
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The following message was posted to: PharmPK
s.o.o
The key thing is the minimum effective concentration and minimum
toxic concentration. The difference between the two is the
therapeutic level. As long as the percentage content of the active
ingredient is within the therapeutic level there is no problem. With
reference to your cream the amount of bethamethamesone be it 1% 5% or
10% should not irritate the skin.As long as the percenatages are
within therapeutic range there is no problem
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