BNF for Children 2011-2012

BNFC 2011–2012 13.1.1 Vehicles 551menstrual age, may also require special measures tomaintain skin hydration.13.1.1 VehiclesThe vehicle in topical preparations for the skin affectsthe degree of hydration, has a mild anti-inflammatoryeffect, and aids the penetration of the active drug.Therefore, the vehicle, as well as the active drug, shouldbe chosen on the basis of their suitability for the child’sskin condition.Applications are usually viscous solutions, emulsions,or suspensions for application to the skin (including thescalp) or nails.Collodions are painted on the skin and allowed to dry toleave a flexible film over the site of application.Creams are emulsions of oil and water and are generallywell absorbed into the skin. They may contain an antimicrobialpreservative unless the active ingredient orbasis is intrinsically bactericidal and fungicidal. Generally,creams are cosmetically more acceptable thanointments because they are less greasy and easier toapply.Gels consist of active ingredients in suitable hydrophilicor hydrophobic bases; they generally have a high watercontent. Gels are particularly suitable for application tothe face and scalp.Lotions have a cooling effect and may be preferred toointments or creams for application over a hairy area.Lotions in alcoholic basis can sting if used on brokenskin. Shake lotions (such as calamine lotion) containinsoluble powders which leave a deposit on the skinsurface.Ointments are greasy preparations which are normallyanhydrous and insoluble in water, and are more occlusivethan creams. They are particularly suitable forchronic, dry lesions. The most commonly used ointmentbases consist of soft paraffin or a combination of soft,liquid and hard paraffin. Some ointment bases have bothhydrophilic and lipophilic properties; they may haveocclusive properties on the skin surface, encouragehydration, and also be miscible with water; they oftenhave a mild anti-inflammatory effect. Water-solubleointments contain macrogols which are freely solublein water and are therefore readily washed off; they havea limited but useful role where ready removal is desirable.Pastes are stiff preparations containing a high proportionof finely powdered solids such as zinc oxide andstarch suspended in an ointment. They are used forcircumscribed lesions such as those which occur inlichen simplex, chronic eczema, or psoriasis. They areless occlusive than ointments and can be used to protectinflamed, lichenified, or excoriated skin.Dusting powders are used only rarely. They reducefriction between opposing skin surfaces. Dusting powdersshould not be applied to moist areas because theycan cake and abrade the skin. Talc is a lubricant but itdoes not absorb moisture; it can cause respiratoryirritation. Starch is less lubricant but absorbs water.Dilution The BP directs that creams and ointmentsshould not normally be diluted but that should dilutionbe necessary care should be taken, in particular, toprevent microbial contamination. The appropriate diluentshould be used and heating should be avoidedduring mixing; excessive dilution may affect the stabilityof some creams. Diluted creams should normally beused within 2 weeks of their preparation.13.1.2 Suitable quantities forprescribingSuitable quantities of dermatological preparationsto be prescribed for specific areasof the bodyArea of the bodyCreams andOintments LotionsFace 15–30 g 100 mLBoth hands 25–50 g 200 mLScalp 50–100 g 200 mLBoth arms or both legs 100–200 g 200 mLTrunk 400 g 500 mLGroins and genitalia 15–25 g 100 mLThe amounts shown above are usually suitable forchildren 12–18 years for twice daily application for 1week; smaller quantities will be required for childrenunder 12 years. These recommendations do not applyto corticosteroid preparations.13.1.3 Excipients andsensitisationExcipients in topical products rarely cause problems. If apatch test indicates allergy to an excipient, then productscontaining the substance should be avoided (seealso Anaphylaxis, p. 159). The following excipients intopical preparations may rarely be associated withsensitisation; the presence of these excipients is indicatedin the entries for topical products. See also Excipients,under General Guidance, p. 2.BeeswaxImidureaBenzyl alcoholIsopropyl palmitateButylated hydroxyanisole N-(3-Chloroallyl)hexaminiumchloride (quater-Butylated hydroxytolueneCetostearyl alcohol (includingcetyl and stearyl Polysorbatesnium 15)alcohol)Propylene glycolChlorocresolSodium metabisulphiteEdetic acid (EDTA)Sorbic acidEthylenediamineWool fat and related substancesincludingFragrancesHydroxybenzoates (parabens)lanolin 11. Purified versions of wool fat have reduced the problem13 Skin