9/23 Chapter 10 Semisolid Dosage Forms: Ointments, creams and gels Flashcards
1. Describe ointments, creams and gels 2. Differentiate between the various types of ointment bases 3. List the criteria for the selection of an ointment base to treat a topical affliction 4. Describe the methods to incorporate an active ingredient into an ointment base 5. Compare and contrast an ophthalmic ointment base and a topical ointment base for application to the skin 6. List reasons for administering drugs nasally, rectally and vaginally
Describe Ointment
• Semisolid preparation intended for external application to skin or
mucous membranes
• May be medicated or not
• Ointment bases may be used for their physical effects or as vehicles
for medicated ointments
Name the 4 Ointment Bases
- Oleaginous
- Absorption
- Water-removable
- Water-soluble
Describe the characteristics of Oleaginous (or hydrocarbon) bases. (1 of 4 Ointment Bases)
Has an emollient effect Protects against escape of moisture Effective as occlusive dressings Remains on skin for long periods of time **Difficult to wash off due to immiscibility with water**
Examples of Oleaginous bases
Petrolatum – Also known as (AKA), yellow petrolatum and petroleum jelly
White petrolatum, USP – AKA, petroleum jelly
Yellow ointment, USP – AKA, simple ointment
White ointment, USP
Absorption bases (1 of 4 Ointment Bases)
May be used as emollients, are not easily removed from the skin because external phase is oleaginous, and are useful as pharmaceutical adjuncts to INCORPORATE small volumes of aqueous
solutions into hydrocarbon bases
Selection of the appropriate
base depends on number of factors, including:
- Desired release rate of drug substance from base
- Desirability of topical or percutaneous drug absorption
- Desirability of occlusion of moisture from skin
- Stability of drug in the base
- Effect, if any, of the drug on consistency or other features of the
base - Desire for a base easily removed by washing with water
- Characteristics of the surface to which it is applied
The two types of Absorption Bases
- Permits incorporation of aqueous solutions resulting in water-in-oil emulsions (W/O) known as anhydrous
- Ones that are in water-in-oil (W/O) emulsions that permit incorporation of additional quantities of aqueous solutions.
Examples of Absorption Bases
- Hydrophilic petrolatum (Type A absorption base)
2. Lanolin (Anhydrous Lanolin) - Type B absorption base
Water-removable bases (1 of 4 Ointment Bases)
They are oil-in-water emulsions (O/W).
Different from absorption bases
.
More easily washed from the skin. Can dilute with water or aqueous solutions.
Absorbs serious discharges
Example of a water-removable base
Hydrophilic ointment
Water-soluble bases (1 of 4 Ointment bases)
Mostly used for incorporation of solid substances
Do NOT contain oleaginous components…greaseless
Softens greatly with water, large amounts of aqueous solutions are not effectively incorporated.
Example of a water-soluble base.
Polyethylene glycol ointment
Selection of the appropriate bases depends on…
- Desired release rate of drug substance from base.
- Desirability of topical or percutaneous drug absorption
- Desirability of occlusion of moisture from the skin
- Stability of the drug in the base.
- Any effect of the drug on consistency or other features of the base.
- Desire for a base easily removed by washing with water.
- Characteristics of the surface to which it is applied
Effects of ointment bases on drug release
- Partition of water-insoluble drug into the skin may decrease in an oleaginous phase due to the drug’s affinity toward the formulation.
- Lipophilic drug release increases when the ointment base shows increased water affinity
- Water-soluble and water-removable bases are preferred for rapid release of lipophillic drugs.
- Water-soluble bases are useful for drugs that contain no water
- Absorption bases can provide greater drug release rates as the base has low affinity for the drug and absorbs water, allowing easier the drug to flow through the ointment matrix.
Two ways to prepare an ointment
- Incorporation
2. Fusion
Describe incorporation
Components mixed until uniform preparation is obtained.
Describe fusion
Components mixed by melting or cooling while constantly mixing.
Methods of manufacture for ointments having an emulsion base involves BOTH melting and emulsification
USP requirements for ointments
Microbial content - Preservatives: Methylparaben, propylparaben, etc.
Minimum fill - ensure proper amount of contents filled
Packaging, storage, and labeling - packaged in large-mouth ointment jars or metal/plastic tubes. Also in a cool place.
Light-sensitive preparation are packaged in opaque or light-resistant containers.
Additional Standards - examine for viscosity and in vitro drug release.
Creams
Semisolid preparation containing 1 or more medicinal agents W/O or O/W emulsion.
Used in topical skin and rectal/vaginal
Preferred over ointments because it’s easier to spread/remove.
Gels
Semisolid systems containing dispersions of small INORGANIC molecules or large ORGANIC molecules in an aqueous liquid jellylike vehicle.
May be formulated to make a drug.
Used for skin, eye, nose, vagina, and rectum.
Gelling agents
Sythetic macromolecules, cellulose derivatives, and natural gums.
What are the other semisolid preparations?
Pastes (intended for skin)
Plasters (semisolid adhesives spread on a backing of paper, fabric, moleskin, or plastic) - used for prolonged contact.
Glycerogelatins (15% gelatin, 40% glycerin, 35% water, 10% medicine) - for long-term contact
Preservatives for packaging semisolid preparations
Parabens, phenols, benzoic acid, quaternary ammonium salts or sorbic acid.
Semisolids used in Dermatological preparations are…
Describe Dermatological medications
Ointments, creams, gels, pastes, and plasters.
Used for treating skin diseases, in which the drug penetrates and be retained in the skin for a period of time.
Substances with both aqueous/lipid solubility are good candidates for passive diffusion through the stratum corneum. Once through, can pass through even deeper.
Available for absorption into the general circulation.
Name types of drugs that wuld absorb in the general circulation.
Nasal, Rectal, Dermatological, Transdermal,
Transdermal dermatological preparations
Ointments, creams, and gels are designed to deliver a drug through the skin to the general circulation.
Contains penetration enhancers: Dimethyl sulfoxide, ethanol, PEG, urea, Spans, Tweens, and lecithin.
