Objectives
1. Describe the physical properties of ointment bases and determine the purposes for which they are best suited.
2. Extemporaneously prepare each type of ointment base and incorporate a solid drug into it.
3. Relate the composition and type of ointment base to the release of a drug contained therein.
Introduction:
Ointments are semi-solid preparations rubbed over the skin to aid in healing, to relieve symptoms like itching and to soothe aches and pains. There is evidence that ointments, creams and balms have been used for many centuries. Modern ointments fall into the category of prescription medications or over-the-counter products. There are four types of ointment, which are hydrocarbon bases or Oleaginous bases, absorption bases, emulsion bases or Water removable bases and last but not least water soluble bases
Ointments are applied topically for several purposes such as protectants, antiseptics, emollients, kerotolytics and astringents. The vehicle or base of an ointment is of prime importance if the finished product is expected to function as any one of the above categories. In the case of a protective ointment for example, the base serves to protect the skin against moisture, air, sun rays and other external factors. An ointment must not penetrate the human skin barriers and also facilitates the absorption of substances through this barrier. An antiseptic ointment is used to destroy or inhibit the growth of bacteria. Frequently bacterial infections are deeply seated thus a base which has the capacity to either penetrate or dissolve and release the medication effectively is therefore desired. Ointments used for their emollient effect should be easy to apply, be non-greasy and effectively penetrate the skin.
Calculation and formulation
| Salicylic acid | 6%, 1.8g (To be incorporated in 30g of base prepared) | ||
| Sodium lauryl sulfate | 1.0% | 1/100 x30g=0.3g | |
| Propylene glycol (Sp gr. = 1.035) | 12.0% | 12.0/100x30g=3.6g | 3.6g/1.035 gml-1 =3.48ml |
| Stearyl alcohol | 23.0% | 23.0/100x 30g=6.9g | |
| White petrolatum | 24.0% | 24.0/100x30g=7.2g | |
| Purified water | 34.0% | 34.0/100 x30g=10.2g | 10.2g/1.000 gml-1=10.2ml |
| Salicylic acid | 6.0%, 1.8g (To be incorporated in 30g of base prepared) | |
| White wax | 5.0% | (5.0/100)x30g=1.5g |
| White petrolatum | 89.0% | (89.0/100)x30=26.7g |
Result and Discussion:
Evaluation of ointment bases
| | O/W Emulsion Base (Hydrophilic Ointment) | Oleaginous Bases |
| Appearance and consistency | White colour and opaque. In semisolid form. Dry and rough, non -greasy .Fine consistency. | Creamy white colour, translucent and shiny. In semisolid form. Non-granules, very greasy. Fine consistency. |
| Spreadability | More smooth and more easy to spread. | Firm and viscous. Less easy to spread . |
| Washability | Easy to be washed by water. | Difficult to be washed by water. |
Salicylic acid is used for skin treatment. It sheds off the outer layer of skin and so can be used to treat acne, dandruff, corns and warts. It is a fine, water soluble white powder. In our formulations here, it is used externally and is not to be taken orally. In this experiment, salicylic acid is incorporated into both hydrophilic ointment and oleaginous ointment base preparation seperately. It is grounded to fine consistency, so that it can be completely incorporated into the ointment base forming a quality ointment. In part I, the hydrophilic ointment consists of oil-in-water base and thus it is easier to be washed away with water. This is because the external phase is hydrophilic and the internal phase is hydrophobic . It is also easier to be spread on skin, this is due to the presence of sodium lauryl sulfate which reduces the viscosity of our ointment ((lighter consistency, as viscousity is proportional to consistency)). As hydrophilic ointment contains higher water content, it can evaporates quickly and thus when applied onto skin, the cream dry up faster. Therefore, hydrophilic ointment is more preferred for greasy and oily skin. Oil in water emulsion also can penetrate more easily into the skin, so it is better absorbed into the skin. Since it is dryer it is less suitable to be used as emollient. In this hydrophilic ointment, propylene glycol is added in and it works as a humectant, which help to maintain the moisture of our ointment by reducing the escape of water. The white petrolatum added will form an oily film on our skin ,trapping water presence in the skin and so maintaining the moisture of skin. In addition to that, stearyl alcohol acts as a lubricant on the skin surface, softening the skin and giving the skin a smooth appearance. The water soluble components in this ointment are salicylic acid ,sodium lauryl acid, and propylene glycol. The oil soluble components are stearyl alcohol and white petrolatum.
In part II, the oleaginous base is actually an oil base .This oil base of ointment does not spread easily and it stays longer on the surface of skin ,this is because oleaginous base contains very little amount of water in it (anhydrous). It is water insoluble instead. Thus it is not easily being washed away by water. Besides that , it does not get absorbed into the skin, so it is usually prescribed for dry skin and not intended for penetration of drug into skin. It also promotes healing as it keeps the skin moist for longer period of time, slowering the rate of evaporation of skin water. White wax is added as a thickening agent which enhances the viscosity of our skin. It has emollient, soothing and softening properties as well ,helping the skin to retain moisture. It is also water insoluble and thus it is used to produce hydrophobic ointment. Since the base is immiscible with salicylic acid, white petrolatum is added to wet the salicylic acid powder in order for it to be easily incorporation into the oil base .
Conclusion:
Hydrophilic (oil in water emulsion) ointment is smoother and has higher spreadability compared to oleaginous base, this is due to the lighter consistency of it. Hydrophilic ointment is water washable while oleaginous base is water non-washable.
References:
References:
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