(1) Ointments, Creams and Gels: Semi-Solid Dosage Forms

OINTMENTS

a. Definition

b. goal

a. Semisolid preparations for external (topical) use

b. deliver drug to skin (local effect)

OINTMENTS

Types - overview

• Medicated

• Non-medicated (ointment bases)

OINTMENTS

• Medicated

• Contains API

• Used for skin diseases (e.g., sulfur, zinc oxide)

OINTMENTS

• Non-medicated (ointment bases)

• No drug

• Used for:

  • Moisturizing (emollient) → softens skin

  • Lubricant → reduces dryness

  • Protective barrier → prevents moisture loss

  • Vehicle → carries drug

 CLASSIFICATION OF OINTMENT BASES - overview

1. HYDROCARBON (OLEAGINOUS) BASES

2. ABSORPTION BASES (W/O)

3. WATER-REMOVABLE BASES (O/W)

4. WATER-SOLUBLE BASES

 HYDROCARBON (OLEAGINOUS) BASES

Properties

• Highly occlusive → traps moisture

• Hydrophobic

• Greasy

• Difficult to wash off

• Good for dry skin

HYDROCARBON (OLEAGINOUS) BASES

Examples

• Petrolatum (Vaseline)

• White ointment (95% petrolatum + 5% white wax)

• Yellow ointment (95% petrolatum + 5% yellow wax)

• Paraffin → stiffening agent

• Mineral oil → levigating agent

HYDROCARBON (OLEAGINOUS) BASES

Key Concept

• Occlusion = prevents water loss → hydration ↑

ABSORPTION BASES (W/O)

Types

1. Anhydrous (can absorb water → become W/O)

   • Hydrophilic petrolatum

   • Lanolin

   • Aquaphor

2. Already W/O emulsions (can absorb more water)

   • Cold cream (e.g., Nivea)

ABSORPTION BASES (W/O)

Properties

• Occlusive (less than oleaginous)

• Emollient

• Greasy

• Absorb water

WATER-REMOVABLE BASES (O/W)

Properties

• Less occlusive

• Can be diluted with water

• Less greasy

• Easily washed with water

• Better cosmetic feel

WATER-REMOVABLE BASES (O/W)

Examples

• Vanishing cream

• Acid mantle cream

WATER-REMOVABLE BASES (O/W)

Special Note

contains:

• Water (high %)

• Oil

• Emulsifier

• Humectant (e.g., glycerin)

WATER-SOLUBLE BASES

Properties

• Water washable

• Non-greasy

• Lipid-free

• No microbial growth

• Synthetic (PEG)

• Stable, inert

 WATER-SOLUBLE BASES

important

• Can dehydrate skin

• Can reduce drug absorption (percutaneous)

KEY CONCEPT: PERCUTANEOUS vs TOPICAL

• Topical

  • Drug acts on skin only

• Transdermal (Percutaneous)

  • Drug → bloodstream

Transdermal (Percutaneous)

example

Nicotine patch

SELECTION OF BASE

Factors

1. Drug release rate ⭐

2. Percutaneous absorption

3. Stability & compatibility

4. Drug effect on base

5. Need for occlusion

6. Ease of removal

IDEAL OINTMENT BASE

• Non-irritating

• Non-dehydrating

• Non-greasy

• Stable

• Compatible with drug

• Easily removable

• Good drug release

• Good absorption of water

 PREPARATION OF OINTMENTS - overview

INCORPORATION METHOD

FUSION METHOD

INCORPORATION METHOD

Steps

1. Powder drug → fine particles

2. Add small amount of base

3. Mix using geometric dilution

4. Add remaining base gradually

INCORPORATION METHOD

use what?

Levigating Agents

• Mineral oil → for oily bases

• Glycerin → for water-based systems

Use equal volume of levigating agent + powder

 FUSION METHOD

Used When

• High melting point ingredients

FUSION METHOD

Steps

1. Melt oil phase

2. Heat water phase separately

3. Combine phases

4. Stir continuously

5. Add volatile substances last

 TEST REQUIREMENTS

• No sterilization required (except ophthalmic)

• Must meet microbial limits

  • Staph aureus

  • Pseudomonas aeruginosa

• Contains preservatives

• Minimum fill test

• Check:

  • Viscosity

  • Drug release

PACKAGING

• Tubes

• Jars

• Light-resistant, well-closed

OINTMENTS vs CREAMS - chart

Feature	Ointments	Creams
Composition	~80% oil	~50% water
Texture	Thick, greasy	Light
Absorption	Stays on skin	Absorbed
Use	Dry skin	Oily/wet skin

PASTES

• Ointments with high solid content (~50%)

• Stiffer, less greasy

• More absorptive

• Protective barrier

PASTES

example

Zinc oxide (diaper rash)

GELS

• Jelly-like, semi-solid

• Crosslinked network

GELS types

• Hydrogels → water-based

• Organogels → organic liquid