semisolid dosage forms: creams, ointments, gels

ointments are semisolid preparations intended for external application to _______

skin or mucous membranes (oral, ocular, otic, vaginal)

t/f: topical preparations are only used for local effects

false. may be local or systemic. if it is systemic it is a transdermal

what is notable to consider if a pregnant pt is prescribed a certain cream

whether the cream is a transdermal/has systemic effects

are systemic effects possible from non-transdermal creams

yes. if they are misused (ex: put cream all over body when intended for one area) then too much can get absorbed and reach bloodstream

which pts cannot be given retinols/ vit d derivatives and why

pregnant/nursing pts

-highly teratogenic, cause abnormalities in fetus

what does "absorbed" mean for creams// where is the drug?

in blood or in lymph (not just on skin surface)

breast milk tends to be _________ and causes _______ drugs to accumulate

acidic; basic drugs accumulate

topical vs transdermal products

topical= skin is target organ (may or may not have active drug)

transdermal= designed for systemic effects

what can non-medicated ointments be used for

1. emollients (softening)

2. protective barriers (anti-dehydrants)

3. base or vehicle

explain how protective barrier ointments/ anti-dehydrants (ex: aquaphor) can help in the healing process of wounds

barrier keeps wound sterile

what are the 4 types of bases

1. oleaginous/ hydrocarbon

2. absorption

3. water-removable

4. water-soluble

oleaginous base characteristics

- emollient effect

- prevent moisture escape

- occlusive dressings

- remain on skin for long periods without drying due to immiscibility with water

t/f: while oleaginous bases provide an emollient effect, they may dry out over time

false. there is no water in oleaginous bases so they do not dry out

what could too much moisture on areas of healing lead to? which ointment can help with this?

-too much moisture might cultivate bacterial infections

- oleaginous bases trap moisture BUT they also prevent bacteria from reaching the wound= more sterile

t/f: an oleaginous base helps protect the fluidity of granulation tissue

true. oleaginous bases prevent moisture escape, help with healing, and keep wounds sterile

petrolatum, white petrolatum, yellow ointment, white ointment, and mineral oil are all examples of

oleaginous bases

which type of base is petrolatum? what is it obtained from?

oleaginous; discovered when drilling for petrol/gas

why doesnt petroleum have an expiration date

completely hydrophobic= no bacteria grow in it

what is white petrolatum

decolorized petrolatum

which oleaginous base is often used as a levigating agent

mineral oil (liquid petrolatum)

hydrophilic petrolatum, anhydrous lanolin, lanolin, and cold cream are all examples of

absorption bases

relate absorption base function in relation to water

oleaginous in nature but draws fluid out (absorbs fluid, does not trap it in)

2 types of absorption bases

1. emulsifiable bases- allow water incorporation to form w/o emulsion

2. emulsified bases- already w/o emulsions that allow for more water incorporation

can absorption bases be easily removed from the skin with water? why or why not?

no. external phase is oleaginous

which base is useful as pharmaceutical adjuncts to incorporate SMALL volumes of aqueous solutions into HYDROCARBON bases

absorption bases

t/f: you may mix an aqueous solution with an absorption base to incorporate it into a hydrocarbon base

true

explain why oleaginous/absorption bases often have low pt compliance (what are some cons that annoy pts)

oily and ruins clothes. not easily washed out. pts dont want to wear it even though it is the most effective

identify the hydrophilic component in hydrophilic petrolatum:

cholesterol, stearyl alcohol, white wax, white petrolatum

stearyl alcohol (OH groups are aqueous)

is cholesterol ionic/non? lipophilic or hydrophilic?

nonionic, very lipophilic

= makes a good emulsifying agent

what is lanolin? what is anhydrous lanolin?

purified wax-like substance from sheep wool

- no more than 0.25% of water

anhydrous lanolin: non-hydrophilic, but may draw in a little water

which type of base is lanolin

absorption (oleaginous but may absorb some water)

water-removable bases characteristics

- o/w emulsions resembling creams

- easily washed from skin (must still scrub)

- may be diluted w water/aqs

- can absorb serious discharges

which base is an o/w emulsion resembling creams

water-removable bases

which base can be diluted with water or other aqueous solutions

water-removable bases (outer phase is water)

what kind of discharges can water-removable bases absorb

serous exudates (NOT granulation tissue)

ex: purulent, hemorrhagic

are parabens needed in water-removable bases? why?

yes

1. parabens are preservatives. water-removable bases are o/w so bacteria may grow in H2O

2. parabens also help in not becoming dehydrated/ preventing evaporation/ preserves stability

what is the purpose of sodium lauryl sulfate (SLS)

emulsifier/surfactant; help incorporate oil and water

water-soluble bases characteristics

- NO oleaginous components

- completely water washable/ greaseless

- mostly used to incorporate solids

which base is the most hydrophilic and completely water washable

water-soluble bases

which base has the lowest emollient/ protective effect and is the most likely to evaporate

water-soluble bases

polyethylene glycol ointment is an example of

water-soluble base

if 6-25% of an aqueous solution is to be incorporated in PEG ointment, replace ___g of PEG3350 with an equal amount of __________

50g, stearyl alcohol

identify the base:

-occlusive

-non water washable

-hydrophobic

- greasy

hydrocarbon/oleaginous

identify the base:

-emollient

-occlusive

-anhydrous

-absorb water

-greasy

absorption base

identify the base:

- water washable

- nongreasy

- can be diluted with water

- nonocclusive

water-removable

identify the base:

- water washable

- non-occlusive

-nongreasy

- lipid free

water-soluble

how can we control the release rate of a drug from ointment base? why would we want to?

"like dissolves like"

= lipophilic base will release lipophilic molecule slower than an aqueous molecule

- fast release = acute, need relief now (ex: infection)

- slow release= for longer duration of action (ex: immune)

lipophilic drug X is in a lipophilic base. is this for short or long duration of action?

long duration bc slower rate of release

if we want better penetration of a topical, what kind of drug molecule would you select

cells are made of phospholipid membranes, if we want deeper penetration we need lipophilic drug, rather than aqueous. best drug would have some of both. consider adding penetration enhancer

characterize lipophilic drugs by release rate and penetration

- release slower from lipophilic bases

- penetrate through skin better

when is the following base usually used

- ointment:

- cream:

- lotion:

ointment: dry scaly skin

cream: weeping/oozing surfaces

lotion: intertriginous areas/ friction

2 methods for ointment preparation

1. incorporation-levigation: physically mixed until homogenous

2. fusion: components melted together and cooled w constant mixing

what is one limitation to the fusion method of ointment preparation

all ingredients must be heat stable since fusion requires melting

______ are semisolid dosage forms that may be w/o, o/w, or wwb

creams

t/f: ointments are preferred for mucous membranes, rectal, and vaginal

false. creams

what is vanishing cream

o/w emulsion with HIGH water content

- humectant (preserves moisture/ softens skin)

- forms thin layer after water evaporates

pt A comes in complaining that her cream isnt working. as soon as she spreads it, it disappears and she has to reapply. how would you explain/counsel pt

vanishing cream is o/w emulsion that appears clear as you spread it out and SA increases & water evaporates. tell pt that the drug/oil is on the skin, even if you cant see it

describe the makeup of gels/jellies

suspensions made up of small inorganic particles or large organic molecules in liquid

an organic compound may need to be suspended in _____ before adding to gel

emulsifier (ex: alcohol)

single phase vs two phase gel system

single= macromolecules uniformly distributed w no boundary btwn molecule and liquid

2= gel mass has distinct flocules of particles (ex: magma)

what is magma defined as

- two phase gel system

- when the dispersed phase particle size is large, it may separate out

milk of magnesia

makeup?

use/moa?

ex of magma (2 phase gel system)

gelatinous precipitate of Mg(OH)2

- for heart burn, stomach ulcers, gastritis

- coats surface of stomach, does not stop primary patho (HCl)

t/f: milk of magnesia lowers HCl production responsible for GERD

false. it coats the stomach, it does not stop HCl poduction

Gels may thicken on standing, forming a _______, & must be shaken before use to liquefy the gel & enable pouring.

thixotrope

thixotrope

formed by gel thickening; must shake before using

t/f: a transdermal cream will be found in blood/lymph

true. transdermal implies that it passed through skin and reached blood (systemic)

what is usually added to topical agents to increase transdermal efficacy

penetration enhancers (lipophilic/organic)

= DMSO, EtOH, PG, glycerin, urea, SDS, poloxamers, terpenes

what are penetration enhancers

added to topicals for transdermal prep. they are lipophilic and help active drug pass through all of the skin layers and eventually reach blood

examples of penetration enhancers

DMSO, EtOH, PG, glycerin, PEG, urea, SDS, poloxamers, terpenes

pluronic lecithin organogel

aids in rapid penetration of active drugs through the skin (for transdermals) (penetration enhancer)

what are pastes

semisolid preparations of stiff consistency and contain a high percentage of finely dispersed solids

how are pastes prepared?

whats notable about them?

- made same as ointments or by heating

- they are stiff, remain in place, absorb serous secretion

- stick to hairy parts

which vehicle base would you choose if you need it to stay on skin and not move

paste, plasters

what are plasters

solid or semisolid adhesive masses spread on a backing of paper, fabric, moleskin, or plastic

- provide prolonged contact at site

- can be unmedicated= protection/support (casts)

which type of vehicle is often needed in callouses or corn removal

plasters bc they have prolonged contact that can get past the hard skin barrier. creams will not work

(if pt feels pain, STOP therapy. it has reached viable skin)

layers of epidermis

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

which layer of the dermis is the primary barrier to topicals bc of its thickness

stratum corneum

t/f: the first thing a cream must penetrate is the stratum corneum

false. it must penetrate the top layer of waterproof protein- keratin. stratum corneum is independant and follows it

ways for drug entry through skin

- hair follicles (minor)

- gland ducts (minor)

- epidermis (large)

- hair and glands is minor bc theyre SA is so small

what does the rate of dug movement through keratinized SC depend on

- drug concentration (need higher gradient for penetration)

- aqueous solubility

- o/w partition coefficient

describe preferred solubility of compounds that need to pass through skin. what if skin is broken?

-both aqueous and lipid solubility

- if skin is broken, faster absorption

t/f: generally, topical patches go on thick skin to control penetration

false. they are usually applied to thin skin

= abdominal, pelvic, inner arm

(unless if you are treating the thick skin)

t/f: we can determine the concentration of a drug at the site of absorption of the topical

false. we do not know how much of a drug is on the skin. we can only tell for transdermals since we can take a blood sample.

-for skin, the only way is to do a punch biopsy

-this is why clinical efficacy varies among patients

t/f: unless specified, bandages should not cover topicals

true

t/f: an immediate rxn after applying a topical for the first time is a type 1 hypersensitivity rxn

false. we need to be sensitized first to have an allergic rxn. immediate rxn at first time is usually physicochemical

why do the eyes/ears/nose/vagina need higher monitoring when using topicals

thin and specialized epithelium.

pay attention to microbial and particulate content

how can drugs enter the eye

most= simple diffusion through cornea

alternate= conjunctiva and sclera