Astringents and Lotions BITS-Pilani, Hyderabad Campus

Astringents  The word "astringent" derives from Latin adstringere, meaning "to bind fast".  Definition: Astringent is a drug that reacts chemically with cellular proteins producing limited coagulation which is accompanied with shrinkage of body tissues.  Astringent protects from external irritation and reduces cellular permeability  It also possesses local styptic and local antiseptic actions

Astringents “Nearly all astringents coagulate albumin, tone up relaxed or debilitated condition of muscular fiber, contract both arterioles and capillaries, restrain peristalsis, contract gland ducts, and repress excessive secretions.” Dr. Edward Shook, 1978

Astringents  Astringent medicines cause shrinkage of mucous membranes or exposed tissues and are often used internally to check discharge of blood serum or mucous secretions  This can happen with a sore throat, hemorrhages, diarrhea, or with peptic ulcers. Externally applied astringents, which cause mild coagulation of skin proteins, dry, harden, and protect the skin  Acne sufferers are often advised to use astringents if they have oily skin

Astringents  Therapeutic Uses of astringents:  Cleaning the face and preventing Acne Breakouts  Stopping bleeding  Relieving the discomfort and itching of insect bites, minor abrasions and Athlete’s foot  Haemorrhoids

Astringents  Examples:  very cold water,  rubbing alcohol  zinc oxide  Tannic acid/Tannins

Astringents  Tannins and their source They are phenolic substances found in many plant species. Examples: ▫Geranium maculatum/robertianum ▫Cinnamomum verum ▫Quaercus spp ▫Capsella bursa-pastoris

Emulsions: Lotions and Creams What is a lotion ? ▫It is a biphasic system of immiscible phases stabilized by a surface active agent What is the difference between creams and lotions? If emulsions are liquid, they are called lotions Creams are semisolids and do not flow through an orifice freely under gravitational force Creams show a thixotropic behaviour

Emulsions: Lotions and Creams Emulsions may be formulated of water in oil (w/o), oil in water (o/w), aqueous gel, and silicone in water O/W emulsions are the most commonly formulated. These types of emulsions tend to feel less greasy and have a lower cost formulation because of a higher water content. W/O emulsions have historically been less popular because of a characteristic greasy, oily feel on application to skin

Emulsions: Lotions and Creams Silicone formulation aids may also be used to form stable water-in-silicone (w/Si) or w/o emulsions. These are polymeric surface-active agents with long bond lengths and wide bond angles. This provides for free rotation of functional groups permitting formulations of w/o and w/Si emulsions with exceptional elegance and good coverage when applied to skin

Emulsions: Lotions and Creams Examples of Vehicle Types

Emulsions: Lotions and Creams Factors to be considered while formulation cosmetic emulsions: To what part of the body will the formulation be applied ? At what time of the day, morning or overnight? Will makeup be applied over the product; will clothing come into contact with the product? Will the targeted consumer apply a fragrance to the body after application of the product, and if so, will the fragrances conflict?

Emulsions: Lotions and Creams Selection of emulsifier: The HLB Scale ▫For nonionic detergents of the ester type:

Emulsions: Lotions and Creams Selection of emulsifier: The HLB Scale ▫For ethoxylated esters and ethers, when the saponification value is not known:

Emulsions: Lotions and Creams Selection of emulsifier: The HLB Scale ▫When the hydrophobic portion contains phenols and mono-alcohols without polyalcohols, the equation can be simplified to: ▫Most nonionics fall into this category; manufacturers who provide HLB values in their product specifications most frequently use this formula

Emulsions: Lotions and Creams Selection of emulsifier: The General Rule ▫Mixtures of anionic and nonionic agents obtain the best emulsion ▫Mixtures of cationic and nonionic emulsifiers is not elegant and they do not form stable emulsions ▫Examples of nonionic emulsifiers used in creams/lotions :  Alcohol ethoxylates, Alkylphenol ethoxylates, Block polymers, Ethoxylated fatty acids, Sorbitan esters, Ethoxylated sorbitan esters and Ethoxylated castor oil

Emulsions: Lotions and Creams Relationship between HLB value and water solubility

Emulsions: Lotions and Creams Other common components of emulsions ▫Emollients: Improve spreading property of emulsions on skin – E.g. IPM, Silicone oils ▫Moisturizer/Humectants: Increase and control hydration of skin E.g. Glycerol and Urea ▫Viscosity enhancing agents: increase viscosity of external phase E.g. xanthan gum, cellulose esters ▫Actives: UV absorbers, sunscreens, vitamins ▫Preservatives: For o/w emulsions E.g. Parabens ▫Perfumes and colouring agents

Emulsions: Lotions and Creams Moisturizer ingredients and their functions

Emulsions: Lotions and Creams Emulsifiers

Emulsions: Lotions and Creams Hydrophilic polymers as viscosity modifiers

Emulsions: Lotions and Creams Other polymers and viscosity modifiers

Emulsions: Lotions and Creams Other common ingredients for conditioning the skin

Emulsions: Lotions and Creams The Oil-in-Water Emulsions ▫They are light and non-greasy ▫They show good skin spreadability and penetration ▫They cause a cooling effect because of evaporation of external phase (water) ▫They do not prevent skin drying as compared to w/o emulsions

Emulsions: Lotions and Creams The Oil-in-Water Emulsions: components ▫Lipid(s) + lipophilic thickening agent (MC wax): % ▫Emulsifier with HLB 9-10: 0.5 to 5 % ▫Co-emulsifier (cetosteryl alcohol, behenyl alcohol): 2 % ▫Preservatives (antioxidants, antimicrobials) : q.s ▫Water + hydrophilic thickening agent (carbomer) ad: 100%

Emulsions: Lotions and Creams The Oil-in-Water Emulsions ▫Selection of surfactants ▫To be most effective, surfactants are used in combination ▫E.g.: Steareth-21 (HLB 15.5) + PEG-5-glyceryl stearate (HLB 8.7)

Emulsions: Lotions and Creams The Oil-in-Water Emulsions ▫Selection of co-emulsifier ▫For same fatty acid residue, viscosity decreases if degree of ethoxylation increases ▫For the same degree of ethoxylation, viscosity increases if fatty acid carbon chain length increases

Emulsions: Lotions and Creams The Oil-in-Water Emulsions ▫Viscosity of o/w emulsions depends on: ▫Volume ratio of internal to external phase ▫Type of lipid used : high m.p. lipophilic compounds increase viscosity – from soft semisolid to solid (E.g. petrolatum or liquid paraffin) ▫Presence of thickening agents in lipid phase (E.g. cetosteryl alcohol) ▫Presence of thickening agents in external phase: E.g. carbomer, hydroxypropyl gaur – ultimate means to increase viscosity, may affect spreadability and make the emulsion more tacky in higher amounts

Emulsions: Lotions and Creams The Water-in-Oil Emulsions ▫Advantages ▫Close resemblance to natural lipid layer in stratum corneum ▫Effective skin protection due to lipid layer formation ▫Sustained moisturization because of occlusion ▫Improved penetration into st.corneum ▫Lower risk of microbial growth ▫Liquid at low temperatures (winter sports)

Emulsions: Lotions and Creams The Water-in-Oil Emulsions ▫Typical composition ▫Lipid component : 20 % ▫Lipophilic thickening agent (e.g.: wax) : 1 % ▫Emulsifier system with HLB (3-8): 7 % - 10 % ▫Preservatives (antimicrobials, antioxidants): q.s ▫MgSO4.7H2O  0.5 % ▫Water (+ hydrophilic thickening agent): ad 100 %

Emulsions: Lotions and Creams The Water-in-Oil Emulsions ▫Newer emollients ▫emollient such as esters, Guerbet alcohols, and silicones ▫Selection of a suitable emollient depends on ability of the material to spread on skin with low tack, dermal compatibility, and perceived elegance by the user

Emulsions: Lotions and Creams The Water-in-Oil Emulsions ▫Newer emollients ▫Researchers suggest a correlation of emollient and molecular weight of the emollients. ▫Viscosity of w/o creams has correlated with molecular weight of the emollients used in test formulations ▫High molecular weight co-emulsifiers formulated with high molecular weight emollients gave more stable w/o emulsions

Emulsions: Lotions and Creams The Water-in-Oil Emulsions ▫Newer emollients ▫Anionic emulsifiers are generally inefficient w/o emulsion stabilizers, because more surface active agents are often needed to stabilize these emulsions ▫Sorbitan stearates and oleates are effective emulsifiers when used at 0.5% to 5.0% ▫Sorbitan iso stearates, being branched chain materials, give a very uniform particle size for w/o emulsions

Emulsions: Lotions and Creams The Multiple Emulsions ▫Multiple emulsions are of interest to the skin care formulator because of the elegant appearance and less greasy feel of these formulation types. ▫Benefits of these types of formulations are the claimed sustained release of entrapped materials in the internal phase and separation of various incompatible ingredients in the same formulation.

Emulsions: Lotions and Creams The Multiple Emulsions ▫A suggested technique for forming a w/o/w emulsion is to first create a w/o primary emulsion by combining water as one phase with oil and a lipophilic emulsifier as the second phase in the traditional method. ▫Next, water and a hydrophilic emulsifier is combined with the w/o primary emulsion at room or warm (i.e., 40 0 C) temperature with mixing forming a w/o/w multiple emulsion.

Emulsions: Lotions and Creams The Multiple Emulsions ▫These emulsions typically contain about 18% to 23% oil and 3% to 8% lipophilic emulsifier. The continuous oily phase is stabilized with about 0.5% to 0.8% magnesium sulfate ▫W/O emulsifiers have an HLB less than 6 and are frequently nonionic or polymeric. ▫O/W emulsifiers have an HLB greater than 15 and are ionic with high interfacial activity. ▫For o/w/o multiple emulsions, w/o emulsifiers have an HLB less than 6 with similar properties as a w/o/w w/o emulsifier.

Emulsions: Lotions and Creams Water-in-silicone Emulsions ▫Polydimethylsiloxane is a hydrophobic polymer ▫It is combined with polyethylene-oxide bases to make it hydrophilic E.g.: dimethicone copolyol emulsifiers ▫Newer additions include hydrocarbon chains added to silicone polyether polymers ▫This results in improved aesthetics to oil in silicone emulsions as well.

Emulsions: Lotions and Creams Water-in-silicone Emulsions ▫Silicone co-polyols exhibit high surface activity and function similarly to traditional emulsifiers. ▫Unlike hydrocarbon emulsifiers with higher molecular weights, high molecular weight silicone emulsifiers can remain fluid. ▫This gives very stable viscoelastic films at the water/oil interface

Emulsions: Lotions and Creams Water-Soluble Ointment Bases ▫PEG polymers are available in a variety of molecular weights ▫These materials are water-soluble and do not hydrolyze or support mold growth ▫PEGs make good bases for washable ointments and can be formulated to have a soft-to-hard consistency. ▫PEGs dissolve in water to form clear solutions; they are also soluble in organic solvents

Emulsions: Lotions and Creams Absorption Bases and Petrolatum ▫Absorption bases can serve as concentrates for w/o emollients; water may be added to anhydrous absorption bases to form a cream-like consistency ▫Petrolatum, a component of some absorption bases, has been shown to be absorbed into de-lipidized skin and to accelerate barrier recovery ▫Bases can be made washable by addition of a hydrophilic emulsifier ▫W/O petrolatum creams can be formulated by mixing 50% to 55% petrolatum with a sorbitan sesquioleate at 5% to 10% having an HLB of about 3 to 7 in one phase and water in a second phase. Both phases are blended at 67 0 C to 70 0 C with mixing

Emulsions: Lotions and Creams

Preservatives in creams and lotions ▫Microbial contamination with pathogenic microorganisms can pose a health risk to the consumer, especially from Pseudomonas infection in the eyes or from an existing illness ▫Microbial contamination may cause an emulsion to separate and/or form off-odors. ▫Contaminated products are also subject to recall, which is undesirable from a commercial viewpoint.

Emulsions: Lotions and Creams Preservatives in creams and lotions ▫Preservatives can be divided into two groups:  Formaldehyde donors  those that cannot produce Formaldehyde

Emulsions: Lotions and Creams Preservatives in creams and lotions ▫Formaldehyde donors  DMDM hydantoin,  Diazolidinyl urea  Imidazolidinyl urea  Quaternium 15  The parabens (esters of p-hydroxybenzoic acid)

Emulsions: Lotions and Creams Preservatives in creams and lotions ▫Non Formaldehyde preservatives  Kathon GC  Phenoxyethanol  Iodopropunyl butylcarbamat