Ointments and Pastes part 1 Flashcards
1) What are the 3 major layers in the structure of the skin, explain what they are composed of?
2) Give 3 examples of appendages of the skin
1.
A) Epidermis
- Outer layer is Stratum Corneum (horny layer) which is composed of dead cells
- The deeper part of the epidemis (stratum germinitivam) has viable cells.
- Turnover of cells takes about 3 weeks
- Stratum corneum controls percutaneous absorption of drugs and other chemicals
- SC thickness varies in different parts of the body
- SC will swell several-fold in water –> affecting barrier properties.
B) Dermis
- Lies directly beneath and supports the Epidermis
- Consists of collagen and elastin
- Contains blood vessels, nerves, hair follicles, sweat and sebaceous glands
- Hair follicles and sweat and sebaceous glands pass through the epidermis to the skin surface
C) Subcutaneous (hypodermis)
- Loose connective tissue and fatty layer
- Thermal barrier, mechanical padding
2.
- Hair follicles
- Apocrine glands
- Eccrine glands
Skin is an effective selection barrier, but where can molecules get through and exert its effects?
- Past the stratum corneum, can permeate more easily through the living tissue
- Most absorption into skin occurs via the lipid components between the cells of the stratum corneum.
Describe the passage of medicament from topical dosage form into skin
What are semi solids?
- Creams, ointments, pastes, gels
- Single phase products – some ointments and gels
- Dispersions – ointments with powdered medicaments, pastes, gels (colloidal)
- Two phase products – creams (o/w or w/o), some absorption base ointments
For ointments;
A) What are they used for?
B) What properties allow it to be spreadable?
C) Where in the body are they helpful?
A)
- Semi-solid preparations intended for application to the skin or mucous membranes, usually containing one or more medicaments dispersed, dissolved or emulsified in a base
- Consistency that permits application to the skin by inunction (rubbing of oinment/oil into skin)
B)
- Viscosity of base (plastic flow with yield value) allows spreading of ointment on skin
C)
- Medicaments may be intended to act on or in the skin or be absorbed for systemic effect
What are some advantages and disadvantages of ointments?
Advantages
- Often occlusive – preventing moisture loss from skin
- Low trauma on application – lubricant action
- Extended duration of action – retained at site of application
- Hydrophobic bases avoid dilution with secretions from mucosa eg eye, rectum
Disadvantages
- Greasy – lack of patient acceptability
- Difficult to remove
- Staining of clothes
- High viscosity ointments are difficult to apply
- Drug release may be poor
What are the target areas for ointments in the skin, give some examples of the ointments?
- Surface: barrier ointments, lip balm, anti-infectives
- Stratum corneum: emollient, keratolytic ointments
- Epidermis: corticosteroid, antiproliferative (eg coal tar) ointments
- Appendages
- Dermis: corticosteroids, rubefacient (eg methyl salicylate) ointments
- Systemic: glyceryl trinitrate
What are some ideal properties for an ointment base?
- Stable
- Inert
- Non-greasy
- Non-irritating – low sensitisation index
- Non-dehydrating
- Good washability (easily removed by water)
- Compatible with all medication
- Free from objectionable odour
- Non-staining
- Efficient on dry, oily or moist skin
- Medium for chemicals soluble in either fat or water
- Made from readily available ingredients of known chemical composition
- Capable of holding 50% water
- Easily compounded
- Melts or softens at body temperature
What are the four main types of ointment bases?
- Hydrocarbon
- Absorption
- Water miscible
- Water soluble
