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Presented at the Advisory Committee for Pharmaceutical Science
meeting on March 12, 2003by
Lucinda Buhse, Ph.D.
Topical Drug Nomenclature
Objective: To establish a scientific basis for a systematic and coherent classification of dosage forms for topical drugs.
Working Group (ONDC/OGD/DPA): Cindy Buhse, Gil Jong Kang, Saleh Turujman, Mamta Gautam Basak, Chi Wan Chen
DPA Laboratory Team: Dick Kolinski, Nick Westenberger, Anna Wokovich, Jack Spencer
Current FDA Definitions
•Cream: A semisolid dosage form containing one or more drug substances dissolved or dispersed in a suitable base.
•Gel: A semisolid system consisting of either suspensions made up of small inorganic particles or large organic molecules interpenetrated by a liquid.
•Lotion: "The term lotion" has been used to categorize many topical suspensions, solutions and emulsions intended for application to the skin.
•Ointment: A semisolid preparation intended for external application to the skin or mucous membranes.
What are the distinguishing properties?
Physico-chemical• Viscosity
• Loss on Drying (LOD)
• Specific Gravity
• Surface Tension
• Water Solubility
• Water Absorption
• Drying Properties
• Thermogravimetric Analysis (TGA)
Chemical•Base Composition
Physical Properties•Appearance•Feel•Microscopy
Appearance•Clear, translucent or opaque
•viscous
•Greasy vs. non-greasy•Cooling sensation
Feel
Physical Properties
Microscopy - 400x
No Peak
Soft Peak Stiff Peak
Creams and Lotions: Multivariate Analysis of Selected Physico-chemical Properties
Viscosity is potentially a significant variable.
Scores Loadings
Lotions Creams
Viscosity Measurements of Selected Topical Products
0
25,000
50,000
75,000
100,000
125,000
150,000
175,000
200,000
Selected Products
Vis
cosi
ty (
cp)
Lotions
Creams
30,000 cp
Lotions are pourable (viscosity <30,000 cp at 5 rpm and 25ºC).
Viscosity of Selected Topical Products
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
1,600,000
1,800,000
2,000,000
Selected Products
Vis
cosi
ty (
cp)
CreamsOintments
Ointments <20% and Lotions >50%.
%Loss on Drying for Selected Topical Products
0
20
40
60
80
100
Selected Products
% L
oss
on
Dry
ing
LotionsCreamsOintments
Chemical Composition of Selected Topical Products
0
20
40
60
80
100
Selected Products
% h
ydro
carb
on a
nd
pol
yeth
ylen
e gl
ycol
Lotions
Creams
Ointments
Ointments have %hydrocarbon or Polyethylene Glycols >50%.
Chemical Composition (%) vs. Loss on Drying (%)
0
20
40
60
80
100
0 20 40 60 80 100
%LOD
% h
ydro
carb
on a
nd
pol
yeth
ylen
e gl
ycol
Lotions
Creams
Ointments
Common Characteristics of Most Marketed Gels
• Viscosity: low (10,000 - 70,000 cp)
• Loss on Drying : high (70-99%)
• Solubility : water soluble
• Water Absorption : no specific trend
• Drying Properties : no specific trend
• Thermogravimetric Analysis : fewer transitions
• Composition : contains gelling agents (carbomer)
• Appearance : clear
• Feel : non greasy, cooling
• Microscopy : no specific trend
0.00 100.00 200.00 300.00 400.00 500.00Temp [C]
0.00
20.00
40.00
60.00
80.00
100.00
%TGA
cream
cream cream
cream
gel
gel
Thermal Analysis - TGA"Drug B"
Gel formulations have fewer transitions than the creams.
0.00 100.00 200.00 300.00 400.00 500.00Temp [C]
0.00
25.00
50.00
75.00
100.00
%TGA
lotion
cream
gel
Thermal Analysis - TGA"Drug C"
Thermogravimetric Analysis of Selected Products
Drug B Drug CCream
Cream
Cream
Cream
Gel
Gel
Lotion
Cream
Gel
Classification of Topical Drugs
Lotions:– pourable with viscosity <30,000 cp (at 5 rpm and 25ºC)
– Loss on Drying > 50%
Ointments:– Loss on Drying < 20%
– hydrocarbon or polyethylene glycols content > 50%
Gels: – contain sufficient gelling agent to form 3D matrix