creams, lotions and ointments

Ph. Eur Definition of Creams

Creams are multiphase preparations consisting of a lipophilic phase and an aqueous phase

when to prescribe ointment vs cream

• acute conditions = ointment

• chronic conditions = cream

hydrophilic creams (washable)

• o/w emulsion (thin, white, smooth)

• absorb water easily = miscible with skin secretion

• disperse phase = fluid/solid at room temp (oil)

• continuous phase = aqueous

• emulsifier = low HLB co-surfactant + higher HLB surfactant (ionic/non-ionic)

lipophilic creams (greasy/non-washable)

• w/o emulsions (emollient)

• protective oily layer on skin as water evaporates

• produced with wool alcohols and sorbitan esters

• dispersed phase = aqueous

• continuous phase = fluid/solid at room temp (oil)

• emulsifier = low HLB surfactant + high HLB co-surfactant

in vitro method for evaluating drug delivery in creams

franz diffusion cell

• formulation applied to donor compartment

• samples taken from receptor chamber

• allows estimation of permeation profile

Ph. Eur Definition of an Ointment

An ointment consists of a single- phase basis in which solids or liquids may be dispersed

what are ointments

• greasy, single phase semi-solids (solid at rest, low stress applied = flows)

• non-irritant and non-sensitising

use of non-medicated ointments

hydration of dry skin

• occlusivity = traps moisture on skin surface and hydrates

when to choose an ointment

• when occlusion required in very dry skin

• if deep drug penetration required

• smaller area of application than creams

advantages of ointments

• high levels of occlusion (prevents water loss - only if required)

• prolonged contact time with required site = time for drug release

• reduced water content

  • longer shelf life, reduces need for preservatives = reduced allergic reactions

  • chemical stability (for drugs prone to hydrolysis)

• easily spread (self administered, adherence)

disadvantages

• greasy, difficult to remove (cosmetically unacceptable)

• stains clothing

• cannot apply to sites that are actively bleeding/discharge

• erratic drug release (if poor drug solubility in base)

four classifications of ointments bases

• oleaginous (hydrocarbon) base

• absorption base

• emulsifying base

• water soluble base

properties of oleaginous bases

• oily = emollient

• occlusive

• highly lipophilic (cannot absorb water = water insoluble)

• non-washable/ irritating / reacting

types of oleaginous (hydrocarbon) bases

• hydrocarbons

• vegetable oils and animal fats

• hydrogenated and sulphated oils

• alcohols, acids, esters

• silicones

oleaginous bases - hydrocarbons

• mix of hydrocarbons from petroleum

  • C₁₆-C₃₀ fluid hydrocarbons entrapped in C₃₀-C₅₀ matrix

• petrolatum = purified mix (yellow, white)

• paraffin wax = solid derived from petrolatum, melts at body temp

• liquid paraffin = mineral oil of hydrocarbons (lubricant)

oleaginous bases - veg oils, animal fats

• consists of mono-, di-, triglycerides of mixtures of saturated and unsaturated FAs

• uses

  • emollient, softening agent, lower MP of base

• decompose after air, light, high temp exposure (rancidity)

• trace metal contaminants (antioxidants - BHA, chelators - EDTA)

• patient sensitivity

properties of absorption bases

• anhydrous, absorb large amounts of water

• occlusive

• hydrophilic

• non-washable

• emollient

• poor chemical stability, likely for microbial contamination

components of absorption bases

• made from hydrocarbon base with miscible polar substance (w/o emulsifier)

  • hydrophilic petrolatum - aquaphor

  • anhydrous lanolin (wool fat)

function of the polar substance (w/o emulsifier) in absorption base

facilitates soaking up of water/skin secretion

if too much water added to absorption base, it becomes

a w/o emulsifying ointment

emulsifying base

• semi-solid emulsion

• more amounts of water than oleaginous/absorption bases

• types

  • w/o, o/w

w/o emulsifying base

• anhydrous base + w/o emulsifier (like absorption)

• higher water content = hydrous but poorly washable (w/o nature)

• incorporate solids, oily solutions and aqueous solutions of drug

examples of w/o emulsifying base

hydrous lanolin, cold cream, eucerin

emulsifiers of w/o emulsifying bases

long chain fatty alcohols/ sorbitan monooleate (low HLB, <8)

• cetyl/steryl/cetostearyl alcohol, sorbitan monooleate

o/w emulsifying base

• anhydrous bases + o/w emulsifiers = hydrous, water miscible ointment

• readily washable

• non-occlusive

• incorporate solids and aqueous solutions of drug

examples of o/w emulsifying base

hydrophilic ointment, dermabase

emulsifying agents for o/w emulsifying bases

ionic and non-ionic surfactants (high HLB >9)

• SLS, cetrimide, cetomacrogol

water soluble base

• no oleaginous base component

• non-occlusive, non-greasy

• washable

• incorporate some water, solids of drug

• formulated using polyethylene glycol blends

hydrophobic antioxidants

• butylated hydroxy-, toluene, anisole (BHT,BHA - 0.005-0.2%)

• ethyl/propyl/dodecyl- gallate (<1%)

• alpha-tocopherol

hydrophilic antioxidants

• sodium sulphite (0.1%)

• sodium metabisulphite (0.01-0.1%)

what can be added to hydrophobic bases

non- polar solvents

types of non-polar solvents

• liquid silicone (PMDS) - barrier ointments, protects skin from water soluble irritants

• veg oil - replace mineral oils, improves properties of absorption bases (coconut/arachis oil)

• propylene glycol - disperse drug through base