# Presentation: 351534

## Presented at the 

**Advisory Committee for Pharmaceutical Science**
**meeting on March 12, 2003**
**by**
**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

**Notes:**
Here I list the variables we looked at in the lab.

## Physical Properties

- Clear, translucent or opaque
- viscous

**Physical Properties**

**Microscopy - **400x

**Notes:**
Point out that these properties are mostly subjective, but become necessary in borderline cases.  

## Creams and Lotions: Multivariate Analysis of Selected Physico-chemical Properties

- Viscosity is potentially a significant variable.

- Scores

- Loadings

- Lotions

- Creams

## Lotions are pourable (viscosity <30,000 cp at 5 rpm and 25oC).

## Slide 8

## Ointments <20% and Lotions >50%.

## Ointments have %hydrocarbon or Polyethylene Glycols >50%.

**Notes:**
The same sample had low hydrocarbon or polyethylene glycol content.  

## Slide 11

## 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

**Notes:**
Here are some general properties of gels although  not all gels fall into these generalizations.  The only absolute is the presence of a gelling agent.  All the gels we have examined in the lab contain carbomer.

## Gel formulations have fewer transitions than the creams.

- Thermogravimetric Analysis of Selected Products

- Drug B

- Drug C

- Cream
- Cream
- Cream
- Cream
- Gel
- Gel

- Lotion
- Cream
- Gel

**Notes:**
We are pursuing TGA because we see some interesting differences between gels and creams.

## 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

**Notes:**
Here I show the conclusions from the laboratory data.  I will talk about creams being a default definition.  Chi-Wan will show the detailed definitions.