Dosage Form I Lab notes

Creams

Creams are semi-solid emulsions containing solutions or suspensions of the medicinal agent designated for application to skin or to wounds. They are less viscous than ointments and may be either o/w or w/o. Creams are usually preferred to ointments because they are not as greasy and are easily applied.

Emollient, cold or night cream

Emollient creams conserve the water of the horny layer of the skin against the environment. The fatty film introduced by this cream occludes the water and so it is also called an occluding agent. Emollient creams are used at night for nourishing the skin and as soothing agents for chapped skin. These creams are usually greasy, which is why theyre used at night.

These creams may be o/w or w/o, but w/o is recommended to produce better emolliency. W/o creams may contain 45 80% oil content. To ensure good spreadability, the melting point of the oil-phase should not be more than 37C. Cold creams produce a soothing and cooling effect when applied to the skin. The cooling effect is produced by the slow evaporation of the water content of the cream which takes its latent heat of evaporation from the skin. Glycerol is not needed in creams with very high oil content.

Beeswax borax cold cream:

Beeswax borax cold cream is self emulsifying, i.e. the emulgent is a product of reaction between borax and the free fatty acids of oil and beeswax. Borax can be calculated as follows:

Rx

Purified water24gBorax?gOlive oil50gWhite beeswax12.5gWhite soft paraffin12.5g

Mol. Wt. of Borax = 381.43 g/molMol. Wt. of KOH = 56.11 g/mol

Acid value of olive oil 2Acid value of beeswax20

Acid value is the amount of KOH (in mg) required to neutralize 1g of oil or fat.

Since we have 50g of Olive oil in our master formula, and an acid value of 2, well need 50 X 2 = 100mg of KOH to neutralize the olive oil. And since we have 12.5g of beeswax and an acid value of 20, well need 12.5 X 20 = 250mg of KOH to neutralize the beeswax.So, well need a total of 100mg + 250mg = 350mg of KOH.

NaB4O7 + 3H2O 2H3BO3 + 2NaBO22NaBO2 + 4H2O 2H3BO3 + 2NaOH

As we can see by the hydrolysis of borax, each mole of borax produces two moles of NaOH.And since NaOH is equivalent to KOH, we can calculate borax as follows:One mole of borax 2 mol NaOH = 2 mol KOH

381.43 g/mol --------- 2 X 56.11 mg KOHX--------- 350mg KOH

X = 1190mgIn other words, 1.19g of Borax is required to neutralize the olive oil and beeswax.

Uses of each ingredient:

Borax is a self emulsifying agent.Olive oil is a softening agentWhite beeswax is a stiffening agent. It adds rigidity to the preparation.White soft paraffin is an emollient and is a base to the cream.

Vanishing or day creams

Vanishing creams are an o/w emulsion with 15 30% fat content. The emulsifying agent is a soap formed by the neutralization of 25% of the stearic acid by potassium hydroxide. They are called vanishing creams because they seem to disappear when rubbed into the skin; which makes them appropriate for use during the day.

Uses of each ingredient:

Stearic acid is an emollient. 25% is saponified by the potassium hydroxide; most of the rest is emulsified by the soap formed.Glycerol is a humectant. Humectants help improve the spreading properties of the cream and preserve its consistency. They minimize the drying out of the cream on exposure to the air.Potassium hydroxide saponifies 25% of the stearic acid.

Amount of KOH can be calculated as follows:

RxPurified water79 g Stearic acid15 gGlycerol5 gPotassium hydroxide?gPerfume and preservativeq.s.

Mol. Wt. of stearic acid = 284.5 g/molMol. Wt. of potassium hydroxide= 56.11 g/mol

Amount of KOH required to neutralize 25% of stearic acid:25% stearic acid = 15g x 25/100= 3.75 g CH(CH)CHCOOH + KOH CH(CH)CHCOOK+ HO1 mole stearic acid ........... 1 mole KOH 1 x 284.5 g/mol ............ 1 x 56.11 g/mol3.75 g .............. XX (amt of KOH) = 3.75g x 56.11 / 284.5 X = 0.74 g

All purpose cream

All purpose creams are suitable for hand, face and body, as an emollient, cleansing and foundation base. All purpose creams can be either w/o or o/w but most products are w/o emulsion systems. The w/o creams have an emollient oil phase with a melting point of 35 - 45C. These creams are based on lanolin adsorption bases.

RxLiquid paraffin 23 gLanolin 10 g Beeswax 2 g Stearic acid 15 gGlycerin 12.2 gTween 80 1.5 gWater 36.8 g

Uses of each ingredient:

Liquid paraffin is used as an emollient and a cleanser.Lanolin is used as an adsorption base.Beeswax is a stiffening agent.Glycerin is a humectant. Its also an emollient and a softening agent.Stearic acid is an emulsifying and softening agent.Tween 80 is a solubilising agent.Water is a solvent.

Shaving cream

There are two types of shaving creams: Brush shaving creams, which have to lather, and brushless shaving creams, which do not lather. In our DF1 lab, we prepared a brushless shaving cream.

Shaving creams are o/w emulsions. O/w means it can be easily removed by water. They usually consist of mineral oil emulsified in water with a stearic soap. We use KOH because potassium soaps are more soluble in water than sodium soaps. More soluble in water means that it more readily comes in contact with hair and becomes effective more quickly. Potassium soaps produce a finer, denser lather than the corresponding sodium soaps.

Shaving creams should have the following properties:

1. They must keep the beard moist during the shave.2. They must lubricate the movement of the razor over the beard.3. They must spread easily over the face.4. They must be easily rinsed from the face.

RxLiquid paraffin 4 gLanolin 2 g Potassium hydroxide 1 gStearic acid 15 gGlycerin 4 gPerfume and preservative q.s.Water ad. 100 g

Use of each ingredient:

Purified water is the solvent.Stearic acid is a surfactant.Glycerol is a humectant.Potassium hydroxide is an emulsifying agent and is used in neutralization of stearic acid.Liquid paraffin is an emollient.Lanolin is an emollient and a self-emulsifying agent.

Glycero-Gelatin Suppository:Drug administered by rectal or vaginal route and can be used for local or systemic action. Suppositories and pessaries are drug delivery systems where the drug is incorporated into an inert vehicle. This vehicle is referred to as the base. They are formed by melting the base, incorporating the drug and then allowing them to set in a suitable mould (metal or plastic).Criteria of ideal base: Melt at or just below body temperature or dissolved in body fluids. Solidify quickly after melting. Be easily moulded and removed from the mould. Be chemically stable even when molten. Release the active ingredients readily. Be easy to handle. Be bland, i.e. non-toxic and non-irritant.There are two groups, the fatty bases which melt around body temperature (theobroma oil and synthetic fats) and the water-soluble or water-miscible bases (glycerol-gelatin bases and macrogols).Glycerol-gelatin base are a mixture of glycerol and water stiffened with gelatin. The commonest is Glycerol Suppositories Base BP, which has 14% w/w gelatin, and 70% w/w glycerol. In hot climates the gelatin content can be increased to 18% w/w.There are two types of gelatin: Type A, which is prepared by acid hydrolysis, is cationic and is compatible with substances such as boric acid and lactic acid. Type B, (which was used in the lab) is prepared by alkaline hydrolysis and is anionic and is compatible with substances like icthamol and zinc oxide.Because of the water content, microbial contamination is more likely than with the fatty bases, so preservatives may be added to the product.

Calculations for suppositories:Mould calibration:The capacity of the mould is confirmed by filling the mould with the chosen base. The total weight of the perfect suppositories is taken and a mean weight calculated. This value is the calibration value of the mould for that particular base.Displacement value:The volume of a suppository from a particular mould is uniform but its weight can vary when a drug is present because the density of the drug may be different from that of the base. For example, a drug which has twice the density of the base will occupy half the volume which the same weight of base occupies. Allowance must be made for this by using displacement values (DVs).The displacement value of a drug is a number of parts by weight of drug which displaces 1 part by weight of the base.Example 1:To calculate the DV of a drug, a batch of unmedicated suppositories is prepared and the product weighed. A batch of suppositories containing a known concentration of the required drug is prepared and the product is weighed.Weight of six unmedicated suppositories = 6gWeight of six suppositories containing 40% drug = 8.8gWeight of base is then =60% =60/100*8.8=5.28g.Weight of drug in suppositories = 40/100*8.8=3.52g.Weight of base displaced by drug = 6-5.28=0.72g.If 0.72g of base is displaced by 3.52g of drug, then1g of base will displaced by X.X=3.52g/0.72g=4.88g.Therefore displacement value of drug = 4.9

Example 2:Prepare six suppositories each containing 250g bismuth subgallate.Not all material can be removed from the evaporating basin (porcelain dish) so quantities are calculated for an excess of two suppositories. Therefore calculate for eight suppositories. DV of bismuth subgallate = 2.7 , i.e. 2.7g of bismuth subgallate displaces 1g of base.A 1g mould will be used with mould calibration = 0.94To calculate the amount of base required, a simple equation is used: amount of base = (N*Y) - N*D/DVwhere N is the number of suppositories to be made, Y is the mould calibration, D is the dose of drug in one suppository, DV is the displacement value.Using the terms in the equation for this example: N = 8 ; Y = 0.94 ; D = 250mg = 0.25g ; DV = 2.7 Using the equation: Amount of base required = (8*0.94) - 8*0.25/2.7 = 7.52 - 0.741 = 6.779 g 6.8 gExample 3:Calculate the quantities required to make 15 supp., each containing 300 mg of bismuth subgallate. 2 g mould is to be used. DV of bismuth subgallate is 2.7.

Calculate for 17 suppositories (2 excess)Amount of drug = 0.3g*17 = 5.1gD.V=C/A-D 2.7= 5.1g/34g-D 34g-D= 5.1g/2.7 34g-D = 1.88gD = 34g - 1.88gD = 32.12gOr use a simple equation, amount of base = (N*Y) N*D/DVLet Y =2 ; amount of base = (17*2) 17*0.3/2.7Amount of base = 34 1.88 = 32.12g

Labeling for suppositories:Adequate information should appear on the label so that the patient knows how to use the product. In addition the following information should appear:store in a cool place and for rectal use only or for vaginal use only, whichever is appropriate.do not swallow can be put on the label but do not use for external use only. The preparation is being inserted into a body cavity and this instruction is therefore incorrect.1