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3 Semisolid dosage forms
Creams, Ointments, Gels
Ointments
Semi solid preparation used on the skin and mucous membranes
(body opening with moist lining such as the eye)
2 Main effects of oinments
Local and Systemic
Why must systemic effects of ointments be considered in pregnant or nursing patients?
Harmful drugs can enter fetal circulation and breast milk
What risk does overuse of topical drugs on large areas pose?
Increased absorption → Systemic effect → Overdose
Why is retinol (a Vitamin A derivative) dangerous in pregnancy?
It is teratogenic, which means it causes fetal defects, even in small amounts
How do absorbed topical drugs reach systemic circulation? (2)
Blood and Lymphatic system
Why do weak basic drugs accumulate in breast milk?
Breast milk is acidic, so it traps weak bases such as morphine and acetaminophen
What is the purpose of topical dermatological products?
Deliver drugs into the skin to treat dermal disorders
What is the target organ of topical dermatological products?
Skin
How do transdermal products differ from topical dermatological products?
Delivers drugs thru the skin to reach system circulation
What is the target organ of transdermal products?
Systemic circulation
Why are transdermal products used instead of oral medications?
Special populations that require systemic circulation
Medicated vs Unmedicated dermatological products
Medicated products contain active drugs
Unmedicated products do not contain active drugs
What are 2 functions of non-medicated dermatological products?
Emollients → Softeners
Anti-dehydrates → Retains moisture
What is the role of the base and vehicle in topical preparations?
Base → Provides structure and consistency
Vehicle → Acts as a carrier for active ingredients
What are 2 non medicated ointments that are hydrophobic? What is it used for?
Vaseline and Aquaphor
Physical effects
What is the function of hydrophobic ointments like Vaseline or Aquaphor?
It forms a protective barrier to enhance wound healing
What are the two types of wound healing in which hydrophobic ointments like Vaseline or Aquaphor are commonly used?
Primary wound healing → Closed wounds such as stitches
Secondary wound healing → Open wounds (to recover from bottom up)
What are the two main types of ointment bases?
Hydrophobic and Hydrophilic
Define the following:
Hydrophilic
Hydrophobic
Lipophilic
Lipophobic
Hydrophilic → Attracts water
Hydrophobic → Repels water
Lipophilic → Attracts fat
Lipophobic → Repels fat
4 Major types of semisolid bases
Oleaginous bases
Absorption bases
Water removable bases
Water soluble bases
T/F: Oleaginous bases are greasy and hydrophobic hydrocarbons
T
3 Reasons to use oleaginous (hydrocarbon) bases
Emollient effect (Softener)
Anti-dehydrate protection (Retains moisture)
Occlusive dressing (Barrier, does not allow anything to pass thru)
Why do oleaginous bases remain on the skin for long periods?
It is immiscible with water (does not mix, forms distinct layers)
What prevents bacteria from growing in oleaginous bases?
Lipophilic nature of oleaginous bases
4 Examples of oleaginous bases
Petrolatum
White petrolatum
Mineral oil
Yellow ointment
What is Petrolatum (Vaseline), USP? Where is it produced from?
It is a purified semi solid hydrocarbon
It is a byproduct of petroleum
T/F: Petroleum was originally discovered thru oil drilling
T
How is white petrolatum produced?
Bleaching petrolatum
2 Components of yellow ointment
Yellow wax and Petrolatum
Mineral oil
Liquid oleaginous base
What is mineral oil used for in ointments?
Levigating agent, it helps mix dry powders into a uniform base, unmedicated
T/F: An oleaginous base helps protect the fluidity of granulation tissue (tissue that forms during the healing of a wound)
T
What are absorption bases useful for?
It helps incorporate aqueous solutions into hydrocarbon bases to create W/O emulsions
(An emulsion is a mixture of two immiscible liquids, where one liquid is dispersed in the other in the form of tiny droplets.)
Are absorption bases easily removable by water washing?
No
Emulsifiable absorption base vs Emulsified absorption base
Emulsifiable absorption base → Forms W/O emulsions
Emulsified absorption base → Already in W/O emulsion form, but can incorporate more water
4 Examples of absorption bases
Lanolin
Anhydrous lanolin (anhydrous means without water)
Cold creams
Hydrophilic petrolatum
What is the dominant base in a “water in oil” emulsion?
What is the dominant base in an “oil in water” emulsion?
Oil
Water
What are the four components of Hydrophilic Petrolatum, and what are their functions? (CSWW)
Cholesterol → Emulsifying agent → Lipophilic component
Stearyl alcohol → Emulsifier → Hydrophilic component
White wax → Structure
White petrolatum → Base
What is lanolin derived from?
Purified wax like substance from sheep wool
Key function of lanolin
Retains moisture
Water removable base
Oil in water emulsion that resembles creams
T/F: Water removable bases easily wash off with water but require scrubbing
T
Can water removable bases be diluted with water? Why or why not?
Yes bc the external phase is aqueous
What is the main function of water removable bases?
Absorbs serous discharge for fasting healing
In water removable bases, indicate the components that make up the following;
Oil phase (2)
Water phase (2)
Emulsifier (1)
Preservative (2)
Oil phase → White petrolatum, Stearyl alcohol
Water phase → Purified water, Propylene glycol
Emulsifier → Sodium Lauryl Sulfate (SLS)
Preservative → Methylparaben, Propylparaben
Why do water-removable bases need preservatives?
The high water content increases risk of contamination
Do water soluble bases have any oleaginous components?
No
What kind of semi solid base is completely water washable (greaseless), and does not require scrubbing for removal
Water soluble base
What are water soluble bases used for?
Incorporating solids
What type of semi solid base provides the weakest emollient and least protective effects?
Water soluble base
T/F: The higher the water content, the higher the risk of evaporation.
T
2 Examples of water soluble bases
PEG (Polyethylene Glycol Ointment, 3350 and 400) and NF (National Formulary)
Cholesterol
Nonionic, long fatty chain acid
Can cholesterol serve as an emulsifying agent?
Yes, but it must be a mixture of cholesterol and its esters
In cholesterol, what is the result of increasing OH (hydroxyl group)?
It will increase hydrophilicity
What is used to extract cholesterol?
A liquid hydrocarbon such as chloroform (CHCl3)
What semisolid base is best used for thick, dry, calloused skin (e.g., feet, elbows, knees)?
Oleaginous bases
What semi solid base is best used for wound healing, minor burns, or exuding lesions?
Absorption bases
_____ → Greasy, Occlusive, Emollient, Lipophilic
_____ → Greasy, Occlusive, Emollient, Anhydrous, Absorbs water
Oleaginous base (hydrocarbons)
Absorption base
_____ → Not greasy, Not occlusive, Water washable, Can be diluted with water
_____ → Not greasy, Not occlusive, Water washable and soluble, Lipid free
Water removable base
Water soluble base
What are the 5 key factors influencing base selection in topical preparations?
Action Desired (e.g., occlusive, emollient, water-washable)
Physical and Chemical Properties of the Drug
Patient Compliance Factors (e.g., ease of washing, staining potential)
Bioavailability
Stability
What does the "like dissolves like" principle determine in base selection?
Release rate and Duration
What happens if a lipophilic drug is in a lipophilic base? Release & Duration
Slow release → Long duration (Good for chronic conditions)
What happens if a hydrophilic drug is in a hydrophilic base?
Fast release → Short duration (Good for acute conditions)
Used for dry, scaly skin.
Ointments (Oleaginous)
Applied to weeping or oozing surfaces.
Creams
Applied to intertriginous areas (e.g., skin folds) or where friction occurs.
Lotions
2 Methods for ointment preparation
Levigation → Mix components until uniform
Fusion → Melt components together, it will cool as you mix, stop when congealed
What is a key limitation of the fusion method?
The active ingredient must be stable at high temperature
Why might preservatives or emulsifiers degrade in the fusion method?
Heat labile (lose stability)
Semi-solid dosage form that contain one or more drugs mixed or dissolved in a base. The base can be water-in-oil (W/O), oil-in-water (O/W), or water-washable (WWB) formulations.
Creams
What are creams used for?
Treat skin disorders such as dermatitis or psoriasis
What application is preferred by patients due to ease of application and removal? (Hint: Less staining than ointments)
Creams
2 Applications for creams
Rectal and Vaginal
Vanishing cream
Oil in water emulsion
Since vanishing creams have a high water content, wha does it form after evaporation?
A thin film
What is added to vanishing creams to retain moisture? (GGS)
Humectants such as glycerin, propylene glycol, sorbitol
_____ Formula:
Stearic Acid: 18g
Mineral Oil (Light): 2g
Lanolin: 0.5g
Span 80: 2g
Potassium Hydroxide: 0.7g
Sorbitol Solution 70%: 3.7g
Purified Water: qs ad 100g
Vanishing cream
_____ Formula:
Cetyl Esters Wax: 125g
White Wax: 120g
Mineral Oil: 560g
Sodium Borate: 5g
Purified Water: 190ml
Total: 1000ml
Cream
_____ Formula:
Cetyl esters wax
White wax
Almond oil
Sodium borate
Stronger rose water
Purified water
Rose oil (enhances patient compliance)
Rose water ointment
List 3 W/O emulsion bases that have aqueous mixtures
Eucerin, Nivea, Polysorb hydrate
Semisolid systems consisting of suspensions of small inorganic particles or large organic molecules interpenetrated by a liquid.
Gels
Single phase gel system vs. Two phase gel system
Single phase system → Macromolecules are evenly distributed
Two phase system = Magma → Contains floccules of small distinct particles
Example of magma (two phase system gel)
Milk of magnesium, used for heartburn, coats the stomach lining but does not neutralize hydrochloric acid
Thixotropy
Gels thickens when standing, requires shaking before use
9 Examples of penetration enhancers of transdermal preparations
DMSO, EtOH, PG, Glycerin, PEG, Urea, SDS, Poloxamers, Terpenes.
2 Examples of transdermal preparations
Nicotine patches, Hormone patches
Semisolid dosage forms that contain one or more drug substances for topical application.
Paste
What are paste used for? Provide an example
Protective barrier
Zinc oxide (diaper rash, wounds, eczema)
T/F: Pastes that do not contain active drugs help stabilize medication on the skin.
T
What are the 2 methods to prepare pastes?
Levigation and Fusion
Pastes are used for their stiffness, they remain in place after application and are effectively employed to _____
Absorb serous secretions
Are pastes compatible with hairy parts of the body?
No
Solid/semi-solid adhesive applied to the skin for prolonged contact using backing of paper, fabric, moleskin or plastic
Plasters
What are plasters used for? Provide an example
Dead squamous skin (callous)
Salicylic acid (for corn removal)
What does it mean if you feel a burning feeling when using a plaster?
It has gone too far into viable skin
What is the surface effect of ointments on the skin?
Forms protective layer
What influence do ointments have on the stratum corneum?
Influences hydration and absorption
