Semisolid Dosage Forms - Ointments & creams Flashcards
Advantages of topicals
- often easy application
- local application
- self medication
- no first pass effect
Disadvantages of topicals
- Sometimes not easy application
- Dosage inaccurate
- Messy
What are the different bases
- Oleaginous bases
- Absorption bases
- Water-soluble bases
- Water-in-oil bases
- Oil-in-water bases
Properties of oleaginous bases
- Occlusive
- Emollient
- Difficult to wash - non-water washable
- Greasy
- Hydrophobic
- High index of compatibility with water liable drugs -> very stable
Examples of oleaginous bases
- Petrolatum USP: semisolid hydrocarbons from petrolatum; yellowish to light amber e.g. vaseline
- White petrolatum: purified and decolorized petrolatum USP; lighter in color e.g. White Vaseline
- Yellow Ointment USP: obtained from honeycomb
- mineral oil: liquid hydrocarbon from petrolatum e.g. plastibase
Properties of absorption bases
- composed of oleaginous base and surfactant
- low water content
- hydrophilic
- difficult to spread and wash
- mainly used as protectants and emollients
Examples of absorption bases
- SuperLan
- Lanolin USP
- Hydrophilic petrolatum USP
Properties of water-in-oil emulsion bases
- composed of oleaginous base, a small amt of water and a surfactant
- high water content
- hydrophilic
- easy to spread but difficult to wash
- mainly used as emollients and cleansing creams
Examples of W/O emulsion bases
- Cold creams
- Nivea
- Lanolin (hydrous)
- rose water ointment
- hydrocream
Properties of oil-in-water emulsion bases
- composed of oleaginous base, a large amt of water and a surfactant
- hydrophilic
- high water content
- easily removed with water -> water-washable base
- easily spread, non greasy
- better cosmetic appearance
- mainly used as emollients and drug carriers
Examples of O/W emulsion bases
- hydrophilic ointment
- dermabase
- unibase
Properties of water-soluble bases
- all ingredients are water soluble/washable
- single phase
- non-greasy
- non-occlusive
- can absorb water
- anhydrous/hydrous
- no oil phase, easily spread and washed
- mainly used as drug carriers
Examples of water-soluble bases
- polyethylene glycol ointment - PEG 3350 and PEG 300
- glyceryl monostearate
- carbopol 934
- cellulose, methylcellulose, hydroxyethyl cellulose
How to prepare for ointments?
- Mechanical incorporation: incorporation, levigation
- Fusion: mix ingredients in the melting state
=> depends on the drug solubility in the ointment base
What is levigation
Making into a smooth, fine powder as by grinding when moist; to separate fine particles from coarse by grinding in water
What is incorporation
Mix ingredients together using mortar and pestle and components are reduced to fine powder. Add levigating agent to wet powder. Base and powder are combined uniformly and the final product should be free of gritty feel, should slip
What is fusion
Melt wax (oleaginous base) on water bath and add ingredients (solids in order of m.p. then heat to fusion point and add liquid ingredients); mix phases at the same temp. to make homogeneous and powder is added after base congeals
- Used for solids that cant be triturated easily - beeswax, cetyl alcohol
- Done in porcelain dish, beaker/steel-jacketed kettles
What are the tests for ointments
- Microbial content: determined and controlled amount and type, must meet acceptable standards for microbial contents
- Min fill: determination of the net weight/volume of the contents of filled containers to ensure proper contents compared to the labeled amount
- Packaging and storage: containers should be well closed for protection, stored in a cool place
What are creams
Opaque, soft solids, or thick liquids intended for external application, consisting of medicaments dissolved/suspended in water soluble or vanishing cream bases.
Emulsions of either O/W or W/O type.
Good delivery system
Good patient acceptance
What are lotions
Aqueous preparations with insoluble material for external application typically having low viscosity for easy, rapid and uniform application.
Fluid Emulsions of either O/W or W/O type.
Dry on skin quickly after application.
What are collodions
Liquid preparations composed of pyroxylin dissolved in alcohol ether, with or without added medicinal substances
Used as an adhesive to dose small wounds and hold surgical dressings and topical medications
Disadvantage of inflexible in nature
What are plasters
Solid/semisolid adhesive masses spread upon a suitable backing material used for external application.
Can be medicated or nonmedicated.
What are paste
Semisolid preparation intended for application to the skin; contain a large proportion 20% of solid materials -> thick, stiff ointments that do not ordinarily flow at body temp.
Serve as protective coatings over the areas applied and used to absorb serious secretions
Used for sensitive, inflamed and denuded skin conditions, protect or treat serious skin breakdown; adheres to wet, weepy skin, protecting it from further trauma
What are jellies and their applications
Solid/semisolids preparations where liquid is constrained within 3D network
Applications: drug delivery, lubricants, medicated: intravaginal, nonmedicated: rectal, vaginal, urethral examination procedures
What are topical solutions
Solutions applied to skin where it soaks and baths
e.g. Burow’s solution
What are tinctures
Alcohol based solutions
What are liniments
Alcoholic/oleaginous solutions/emulsions of various substances intended for external application to skin, generally with rubbing
Factors affecting drug penetration
- Drug concentration
- Drug diffusion coefficient
- contact time with skin
- thickness of stratum corneum
- skin condition
- partition coefficient
- presence of surfactants
- drug parameters - MW, adequate solubility in water and oil, particle size (10um remain on skin, 3-10um concentrate in hair follicle, <3um penetrate hair follicle and stratum corneum)
Methods to enhance drug penetration
- hydration
- use of supersaturated solutions
- use of prodrugs - e.g. steroids
- use of penetration enhancers - temporary diminish impermeability of skin, sorption promoters/accelerants
Definition of topicals
Applied to external body surface (skin) including mucosa, virtually anything that is not injected, swallowed or infused.
Describe the different parts of the skin and its functions
- Epidermis - top layer; cells of the basal layer divide, migrate upward to die and form a semi-permeable layer or keratin (stratum corneum)
- Dermis - below epidermis; supplies nutrients, regulates temperature, introduce topical drugs into general circulation, mechanical function, skin appendages are found
- Subcutaneous layer - fat storage area -> cushioning, regulates temp. ; below epidermis
Uses of topicals
- Augmentation of skin’s barrier function e.g. sunscreens, antibiotics for abrasions and emollients for dry skin
- Drug delivery to skin
1. targeted delivery for skin’s outer layers - poor systemic accessibility, lower systemic toxicity,
2. systemic drug delivery e.g. transdermal patches - avoid GI tract, no first pass metabolism, barrier function of subcutaneous limits no. of drugs used (formulate to cross stratum corneum)
Types of topical dosage forms
- Semisolids - ointments, pastes, creams and lotions, jellies
- tinctures
- liniments
- collodions
- plasters
Definition of ointments
Semisolids for application to the skin/mucous membranes which soften/melt at body temp.
Uses of ointments
Protectants, antiseptics, emollients, antipruritics, keratolytic and astringents
Factors to consider for base selection for ointments
- Desirability for topical/percutaneous drug absorption
- Desired release rate of the drug substance
- Desirability of occlusion of moisture from skin
- Drug stability - short-term/long-term
- Influence of drug on consistency of ointment base
- Desire for a base that is easily removed by water
- Patient factor - dry/weeping (oozing) skin
What are gylcerogelatins
Plastic masses intended for topical application and contain gelatin 15%, glycerin 40%, purified water 35% and medicinal substance 10%
e.g. zinc gelatin - contains 10% zinc oxide in glycerogelatin base used for the treatment of ulcers
Factors to consider for semisolid formulation products
- local/systemic effects
- stability of the active ingredients
- rheological properties: consistency, viscoelasticity, extrudability
- loss of volatiles, including water
- phase change: inhomogeneity, bleeding, cracking
- particle size distribution of dispersed phase -> stays on top of stratum corneum/passes through it
- pH change
- Particulate contamination
- Storage
