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Topical administration is employed to deliver a drug at or immediately beneath the point of application. Although occasionally enough drug is absorbed into the systemic circulation to cause systemic effect, absorption is too erratic for the topical route to be used for systemic therapy. A large number of topical medicaments are applied to the skin, although topical drugs are also applied to the eye, nose, throat, ear, vagina etc.
In man, percutaneous absorption probably occurs mainly from surface. Absorption through the hair follicles occurs, but the follicles in man occupy too small a portion of the total integument to be primary importance. When the medicament is rubbed on vigorously, the amount of the preparation that is forced into the hair follicles and glands is increased. Since much of a drug that is absorbed through the epidermis diffuses into the circulation without reaching a high concentration in some portions of the dermis, systemic administration may be preferred in lieu of or in addition to topical administration. Briefly, topical preparations fall into the following categories:
• Protective & Absorbents
• Mechanical & Chemical Protective
• Demulcents Emollients
• Astringents & Antiperspirants
• Irritants, Rubefacients & Vesicants
• Sclerosing Agents
• Caustics & Escharotics
• Keratolytics & Cleansing Preparation
Most commonly used topical preparations are Creams, Ointments and Lotions. In the Ointment category the bases used may be Hydrocarbon Base-They are non water washable, Absorption Base-They absorb water, Emulsion Base or Creams-They may be water in oil or oil in water type and Water Soluble Base-They are non greasy, water soluble and washable.
Ointment & Cream base preparation
Oil Base
Take White Soft Paraffin, Liquid Paraffin, Cetomacrogol 1000 and Cetostearyl Alcohol in a suitable S.S vessel. Melt and maintain a temperature of 70º C - 75º C.
Aqueous Base
Dissolve Sodium Acid Phosphate, Chlorocresol and Phosphoric Acid in distilled water and maintain temperature of 65º C - 70º C.
Slurry preparation
Take distilled water and add Cetomacrogol 1000 & the medicament all in proportionate quantities. Stir well at a temperature of 45º C - 46º C.
Manufacturing Process
Charge distilled water in proportionate quantity to a jacketed S.S. kettle and heat to 65º C. Add and dissolve Sodium Acid Phosphate, Chlorocresol and Phosphoric Acid all in proportionate quantities and maintain temperature of 65º C - 70º C. Mix well till completely dissolved. Cover the batch whenever possible to avoid excessive loss due to evaporation. Do not add additional water to make up the total weight. Take White Soft Paraffin, Light Liquid Paraffin, Cetomacrogol 1000 and Cetostearyl Alcohol in a suitable S.S vessel. Melt and maintain a temperature of 70º C - 75º C. Continue heating & mixing until all the ingredients are completely melted and the mixture is uniform. Pass the melted waxes through 120mesh S.S. screen into the batch of aqueous base while maintaining the temperature of 65º C. Mix for 20-30 minutes. Continue mixing at fast speed and cool by circulation of water till the temperature is 50º C. Stop circulation of water and allow the temperature to drop at 47º C +/- 1º C. Check and adjust the pH to 5.3 +/- 0.1 with 0.1 N Phosphoric Acid solution or 0.1 N Sodium Hydroxide solution. Charge distilled water in proportionate quantity in another suitable S.S. container and heat to 65º C. Add & dissolve proportionate quantity of Cetomacrogol under stirring. Cool to 47º C. Remove proportionate quantity for rinsing. Disperse medicament in the remaining solution by using Turbo Disperser or Colloid Mill, set at 0.005`` gap. Add to the batch which is also at 47º C +/- 1º C and mix until dispersed uniformly. Rinse the container used to prepare the slurry and the Colloid Mill with the remaining proportionate quantity of rinsed solution. Continue slow mixing. Transfer the batch into clean drums lined with double polythene bags and record the weight. Check the final pH and allow to cool overnight.
Cream & Ointment tube filling
Clean the crimping blocks & hopper of the tube filling machine with a good detergent solution. Clean it twice with purified water and dry with electric hand drier. Fill the hopper with ointment/cream. Collect the ointment/cream in the stainless steel cup till confirmation of the uniform flow of the ointment/cream from the nozzle of the bulk. Check the sensitivity on the calibrated Single Pan Balance. Adjust the weight required and check the weight of the ointment/cream on butter paper which has been previously weighed on Single Pan Balance. Check the Batch No., Month & year of Expiry on the crimp of the empty collapsible tube. Collect two collapsible tubes with Batch No., Month & year of Expiry and fix the lower portion of the tube to the filling record of the product. Weight the empty collapsible tubes on calibrated Single Pan Balance. Check the weight of the filled tubes by putting previously weighed tubes in various tube holders each time every half a hour.
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