Lecture 35: Semisolids- Excipients & Bases

What does topical refer to?

Skin is the pharmaceutical target

What does transdermal refer to?

Skin surface is portal for the systemic delivery

What are the layers of the skin?

• Outermost- epidermis

• Dermis

• Hypodermis

What is the skin?

Main interface b/w body & its environment

What are the roles of the skin?

• Permeation barrier

• Sensation

• Secretions

• Immunity

What is the outermost layer of skin?

• Dead keratinocytes

• Followed by stratum corneum

• Living keratinocytes

What are the layers of the epidermis?

1. Stratum corneum, hydrophobic layer (13% water) from dead cells

2. Viable epidermis, hydrophilic layer (70% water)

• Hydrophilic substance cannot penetrate skin easy

• Hydrophobic substance can enter SC but stored inside

What is the dermis?

Hydrophilic layer

What are the 3 main permeation routes through the stratum?

1. Intercellular

2. Intracellular

3. Follicular

What are emollients?

Substances that soften & moisturize the skin & decrease itching & flaking?

What are the topical considerations for API?

• Quality & chemical properties

• Physical state

What are the topical considerations for excipients?

• Physical state

• Excipient compatibility (w/ API, other ingredients)

What are the topical considerations for physicochemical properties of drug product?

Target product profile

What is an occlusive agent?

An ingredient that creates a barrier on the skin’s surface to prevent moisture loss

What are ointments?

• Less than 20% water & volatiles

• More than 50% hydrocarbons, waxes, or polyols

What are pastes?

• Stiff consistency & high percentage (20-50%) of finely dispersed solids (suspensions)

• Do not flow at body temperature

What are creams?

• Contain more than 20% water & volatiles

• Less than 50% hydrocarbons, waxes, or polyols

• Relatively soft, spreadable consistency & can be formulated as either W/O emulsion or O/W emulsion

What are lotions?

• Emulsified liquid

• More fluid than semisolid

• Historically, some topical suspensions such as calamine lotion have been called lotions but nomenclature is not preferred

What are gels?

• Solid or semisolid

• Chemical or physical gel

What do many excipients have?

Dual or multiple functionalities

What are the properties of Hydrocarbon bases (oleaginous)?

• Water-insoluble

• Does not absorb water

• Occlusive

• Emollient

• Not washable w/ water

• Greasy

• Poor drug release

What are the uses of Hydrocarbon bases (oleaginous)?

• Protectant

• Emollient

• Vehicle for drugs prone to hydrolysis

What are the examples of Hydrocarbon bases (oleaginous)?

• Petrolatum USP

• White ointment USP

• White petrolatum

• Vaseline

What are the properties of Anhydrous (absorption bases)?

• Water-insoluble

• Absorbs water forming W/O emulsion

• Occlusive

• Emollient

• Not washable w/ water

• Greasy

• Poor drug release but better for hydrophobic drugs

What are the uses of Anhydrous (absorption bases)?

• Protectant

• Emollient

• Vehicle for solutions & drugs as solids

What are the examples of Anhydrous (absorption bases)?

• Hydrophilic petrolatum anhydrous

• Lanolin

• Aquaphor

• Aquabase

What are the properties of W/O emulsion absorption bases?

• Water-insoluble

• Less occlusive

• Somewhat greasy

• More cosmetically acceptable

• Useful as emollients

• Not water washable

• Contains water

• Absorbs water (limited)

• Fair-good drug release

What are the uses of W/O emulsion absorption bases?

• Emollient

• Vehicle for liquids & solids

• Cleaning

What are the examples of W/O emulsion absorption bases?

• Cold cream USP

• Eucerin

• Hydrous Lanolin

• Hydrocream

What are the properties of O/W emulsion bases?

• Insoluble in water

• Contains water

• Can be diluted

• Nonocclusive

• Non greasy cosmetically elegant

• Water-washable

• Absorbs water

• Fair-good drug release

What are the uses of O/W emulsion bases?

• Emollient

• Vehicle for liquids & solids

What are the examples of O/W emulsion bases?

• Hydrophilic ointment USP

• Unibase

• Dermabase

What are the properties of water-soluble bases?

• Water-soluble

• Water-washable

• Nonocclusive

• Non greasy

• Lipid-free

• Absorbs water (limited)

• Contains water

• Mixes well w/ skin secretions

• Good drug release

What are the uses of water-soluble bases?

• Emollient

• Vehicle for liquids & solids

• Anesthetic

What are the examples of water-soluble bases?

• Polyethylene glycol ointment USP

• Polybase

What are the properties of gel bases?

• Water soluble

• Contains water

• Absorbs water

• May contain alcohol

• Lipid-free

• Water-washable

• Non occlusive

• Non greasy

• Good drug release

What are the uses of gel bases?

• Vehicle for liquids & solids

• Ideal for mucosal applications

What are the examples of gel bases?

• Methylcellulose gel

• Sodium Carboxymethyl cellulose gel

• Hydroxypropyl Methylcellulose gel (Liqua-Gel)

• Hydroxypropyl Cellulose gel

• Carbomer gel

• Poloxamer gel

What does the base you choose depend on?

1. Action or effect

2. Area of application, time/retention, skin/mucosa

3. Incorporated API(s)

What is a desirable property of semisolid bases?

Chemically & physical stable under normal conditions of use & storage