JELLIES

Jellies are transparent or translucent, non-greasy, semisolid preparation generally applied externally.

They are used for medication, lubrication and some miscellaneous applications.

Types of jellies:

Medicated jellies

(i)     Water soluble drugs like local anaesthetics, spermicides and antiseptics are suitable for incorporation in the jellies.

(ii)   They are easy to apply and evaporation of the water content produces a pleasant cooling effect. The medicinal film usually adheres well and gives protection but is easily removed by washing when the treatment is complete.

e.g.       ephedrine sulfate jelly - used to arrest bleeding from nose.

            pramoxine HCl , a local anaesthetic - relieves discomfort of pruritis and haemorrhoids.

            phenylmercuric nitrate - as spermicidal contraceptive.

Lubricant jelly

Catheters, items of eletrodiagnostic equipment, such as cystoscopes, and rubber gloves or finger stalls used for rectal and other examinations require lubrication before use.

The lubricants must be sterile for articles inserted into sterile regions of the body, such as urinary bladder.

For painful investigations a local anaesthetic may be included as in Lignocaine Gel B.P.C.

Miscellaneous uses

The following are more specialized jellies -

(a) Patch testing

Here the jelly is the vehicle for allergens applied to the skin to detect sensitivity. Several allergens may be applied on one person. The viscosity of the jelly and it leaves on drying help to keep the particles separate.

(b) Electrocardiography

to reduce electrical resistance between the patients skin and electrodes of the cardiograph, an electrode jelly may be applied. This contains NaCl to provide good conductivity and often pumice powder which, when applied onto the skin, removes part of the horny layer of the epidermis, the main layer of electrical resistance.

FORMULATION

Pharmaceutical jellies are usually prepared by adding a thickening agent such as tragacanth or carboxy methylcellulose (CMC) to an aqueous solution in which drug has been dissolved.

The mass is triturated in a mortar until a uniform product is obtained.

For the preparation of jellies whole gum is preferred  rather than powdered gum because the former gives a clear preparation of uniform consistency.

The following gelling agents are used for the preparation of jellies.

(i) Tragacanth

the main hydrophilic component of tragacanth that gels in water has been named bassorin - hence, tragacanth jellies are sometimes called bassorin paste.

The amount of gum required for a preparation varies with its use:

(a)    For lubricating jelly 2 to 3%.

(b)   Fro dermatological vehicles about 5%.

(c)    For incorporation of ichthamol, resorcinol, salicylic acid and other medicaments, about 5% is generally used. All formulations contain alcohol and/or glycerol and/or a volatile oil to disperse the gum and prevent lumpiness when water is added.

(d)   They vary in viscosity, due to the natural origin of the gum and variations in milling and storage.

(e)    The film left on the skin tends to flake.

(f)    Viscosity is rapidly lost outside the pH range of 4.5 to 7.0; for example if benzoic acid is used as the preservative.

(g)    They are susceptible to microbial growth.

Example:

Formula           Ichthamol                                1.0 g

                        Tragacanth                               2.5 g

                        Alcohol 90%                           5.0 g

                        Glycerin                                   1.0 g

                        Purified water q.s.                    50.0g

Procedure:

(i)     Alcohol is taken in a 100 ml, wide mouthed jar; and then tragacanth is added to it. (The reverse order may lead to lump formation). Mixed well.

(ii)   Water is added as quickly as possible and mixed.

(iii) Separately ichthamol, glycerin and 10 ml water is mixed. Final weight is adjusted by adding more of water.

2. Sodium alginate

Uses:- As lubricant - 1.5 to 2 % is used.

            As dermatological vehicle - 5 to 10 % is used.

A trace of Ca - salt (CaCl₂) may be added to increase the viscosity and most formulations contain glycerol as a dispersing agent.

Advantage: Sodium alginate has an advantage over tragacanth that is available in several grade or standardized viscosity.

3. Pectin

·         Pectin is a very good gelling agent and is used in the preparation of many types of jellies including edible jellies.

·         Glycerin is used as a dispersing agent and humectant in dermatological jellies.

·         Jellies must be packed in well-closed containers because they lose water rapidly by evaporation and this lose water rapidly by evaporation and this is increased by the susceptibility of pectin gels to syneresis (i.e. exudation of the aqueous phase as a result of contraction of the gel).

4. Starch

Starch in combination with gelatin and glycerin is commonly used for preparations of jellies.

Glycerin in 50% may act as preservative.

Medicaments are incorporated in the cold jelly by trituration.

5. Gelatin

Insoluble in cold water but swell and softens in it. It is soluble  in hot water.

Hot solution contain 2% gelatin forms a jelly on cooling.

Very stiff  (15%) jellies are melted before used  and after cooling to desired temperature are applied with a brush to the affected area. The area is covered with bandage and the dressing may be left in place for several weeks.

Zinc-gelatin jelly (Unna’s paste) is such an example.

Formula:         Zinc oxide                   15g

                        Gelatin                         15g

                        Glycerin                       35g

                        Water                           35g

Procedure:

(i)     Gelatin soaked in water until softened.

(ii)   Glycerin is added and heated over bath until the glycerin is dissolved.

(iii) Adjust the weight to 85 g if necessary by adding more amount of water.

(iv) ZnO is passed through sieve (#120). Required amount is added in small amounts to the molten base with gentle stirring. Stirring is continued until a viscous product is obtained.

(v)   The product so obtained is poured in a tray to a depth of about 1 cm with continuous trituration throughout the operation. When the  mass is set, carefully the mass is cut into pieces of about 1.5cm²  with a blade or sharp knife.

6. Cellulose derivative

Methyl cellulose and sodium carboxy methyl cellulose

1.      produce neutral jellies of stable viscosity.

2.      Have good resistance against microbial  growth.

3.      Clear due to freedom from insoluble impurities.

4.      Produce strong film after drying on the skin.

Use: Sodium carboxy methyl cellulose can be used to prepare lubricating jellies and sterile jellies.

                                    e.g.  lignocine gel - because it can withstand autoclaving temperature.

N.B. Other cellulose derivatives are

                                                            Hydroxy propyl methyl cellulose (Hypermellose)

                                                            Carbomer

                                                            Polyvinyl alcohols.

7. Clays

Gels containing 7 to 20 % of bentonite can be used as dermatological bases.

Disadvantages:

1.      They are opalescent and lack attractiveness.

2.      Their pH is about 9.0 i.e. not suitable for application on the skin.

3.      Residue on the skin is powdery and rather silky.

Preservation of jellies:

Although some bases like clays and cellulose derivative(s) resist microbial contamination but since all the jellies contain large amount of water, therefore must be suitably preserved.

e.g. Methyl paraben 0.1 to 0.2 % is commonly used.

Loss of water can quickly lead to skin formation on jellies and to prevent the hygroscopic substances, e.g. glycerol, propylene glycol or sorbitol solution may be added.

Bases and medicaments sensitive to heavy metals are sometimes protected by a chelating agent e.g. ethylene diamine tetra acetic acid (EDTA)