- t.i.d. (or tid or TID) is three times a day ; t.i.d. stands for “ter in die” (in Latin, 3 times a day).
- q.i.d. (or qid or QID) is four times a day; q.i.d. stands for “quater in die” (in Latin, 4 times a day).
- q_h: If a medicine is to be taken every so-many hours, it is written “q_h”; the “q” standing for “quaque” and the “h” indicating the number of hours. So, for example, “2 caps q4h” means “Take 2 capsules every 4 hours
New trends in Covid 19 shows that most of the countries are witnessing a continuously reduction in the positivity but on the other hand, there are a good number of countries experiencing high positivity rate,
SHOULD WE REMOVE THE MASKS, FOLD OUR SHIRT’S SLEEVES AND GO OUT TO WORK FREELY WITHOUT OBSERVING THE SOPs?
Absolutely no. Remember, presence of a single individual with covid on the surface of the earth is very dangerous NOT UNLESS, Proper Medication is prescribed, otherwise we would be in for several waves.
The general distribution globally is as follows:
Ointment (unguents) are soft semisolid preparations meant for external application to the skin or mucous membrane. They usually contain medicament that is dissolved, suspended or emulsified in an ointment base. They may contain suitable antimicrobial preservatives. Ointments have emollient and protective action on the skin. They are also used to deliver drugs into eye, nose, vagina, and rectum.
Ointments intended for ophthalmic purposes are required to be sterile.
Characteristics of an Ideal Ointment
- It should have high physicochemical stability.
- It should be smooth and not gritty.
- It should melt or soften at body temperature.
- It should be easy to apply.
- Base(s) should be non-irritant and should have no therapeutic action.
- It should be thixotropic in nature.
Advantages of Ointments
- Handling is comparatively easier than bulky liquid dosage forms.
- Chemical stability is more than liquid dosage forms.
- They promote direct application to the affected body part and avoids unnecessary exposure of
other parts to the medication.
- They are suitable for patients sensitive to parenteral and oral routes.
- They prolong the contact time between the medicament and affected region.
- Drugs with extensive first-pass metabolism by oral route can be formulated as topical dosage
Disadvantages of Ointments
- They are bulkier compared to solid dosage forms.
- They have less stability than solid dosage forms.
Classification of Ointments
Ointments are classified on the basis of several factors:
- According to their therapeutic properties with penetration of skin
- According to their therapeutic uses
Based on Therapeutic Properties with Penetration
- Epidermic ointments
- Endodermic ointments
- Diadermic ointments
- Epidermic Ointments: These ointments are intended to produce localized effect on the skin surface. They are not absorbed completely. They are used as protectives, antiseptics, and parasiticides.
- Endodermic Ointments: These ointments are intended to release the medicaments that penetrate into the layers of the skin to produce local action. They act as emollients, stimulants, local irritants and are anti-inflammatory in nature.
- Diadermic Ointments: These ointments when applied to the skin penetrate deeply through the layers of the skin and mix with the blood circulation to produce systemic effect. The ointments
used in the treatment of hemorrhoids are diadermic ointments.
Based on Therapeutic Uses
- Acne treatment—resorcinol, sulphurs
- Antibiotic—bacitracin, neomycin
- Anti-eczematous—hydrocortisone, ichthamol, salicylic acid
- Antifungal—benzoic acid, nystatin, clotrimazole
- Anti-inflammatory—betamethasone valerate, hydrocortisone
- Antipruritic—benzocaine, coal tar
- Antiseptic—ammoniated mercury, zinc oxide
- Astringent—calamine, zinc oxide, tannic acid
- Counterirritant—capsicium oleoresin, methyl salicylate
- Dandruff treatment—salicylic acid, cetrimide
- Emollient—soft paraffin
- Keratolytic—resorcinol, salicylic acid, sulphurs
- Keratoplastic—coal tar
- Parasiticide—benzyl benzoate, gamma-benzene hexachloride (GBH), sulphurs
- Protective—silicones, titanium dioxide, calamine, zinc oxide, petrolatum
The ointment base is an integral part of an ointment preparation and serves as a carrier or vehicle for the medicament.
Ideal Properties of a Base
- Physically, chemically, and pharmacologically inert
- No irritating and nonsensitizing
- Compatible with skin pH and drug
- Good solvent and/or emulsifying property
- Emollient, protective, nongreasy, easily spreadable and removable
- Able to release medicament readily at the site of action
- Pharmaceutically elegant and should possess good stability
- Easily available and economical
Classification of Ointment Bases
Ointment bases are classified into the following categories:
- Oleaginous (hydrocarbon) bases
- Absorption bases
- Water-miscible bases
- Water-soluble bases
Oleaginous (Hydrocarbon) bases: These bases consist of oils and fats and, hence, are hydrophobic in nature, with the least water absorption capacity. Oleaginous bases provide emollient and protective properties by restricting the loss of moisture from the skin and remaining on the skin for prolonged periods. They are occlusive in nature. Removal of hydrocarbon bases from the skin is difficult.
They undergo no action with the skin and are economical. The following are the different types of oleaginous bases:
- Petrolatum (Soft paraffin): It is a purified mixture of semisolid hydrocarbons obtained from petroleum or heavy lubricating oil. It is available in the form of white soft paraffin and yellow soft paraffin.
- Hard paraffin (Paraffin): It is a chemical mixture of solid hydrocarbons obtained from petroleum. It is a colorless or white, odorless, translucent and wax like substance, which solidifies between 50°C and 57°C. It can be used to stiffen ointment bases.
- Liquid paraffin (Liquid petrolatum or white mineral oil): It comprises liquid hydrocarbons
obtained from petroleum. It is a transparent, colorless, odorless and viscous liquid. Practically, it is used along with hard paraffin and soft paraffin to get desired consistency of ointment for easy extrudability from the collapsible tubes and spreadability on the affected part.
The advantages of hydrocarbons bases are as follows:
- They maintain the skin soft by remaining on the surface as an occlusive layer and preventing the
loss of moisture.
- They ensure prolonged contact between skin and medicament due to their stickiness.
- They are almost physicochemically inert, with little tendency of rancidity.
- They can withstand heat sterilization. Hence, they can be employed in the formulation of sterile
- They are easily available and very cheap.
The following are the disadvantages of hydrocarbon bases:
- Prolonged use may result in water logging with maceration of the skin.
- They retain body heat, thereby producing an uncomfortable feeling of warmth.
- They are immiscible with water. Both application and removal after treatment are difficult.
- They are sticky, making the application unpleasant, and might cause staining of clothes.
- They are poor in absorbing exudate from moist lesions as their water absorption capacity is very low.
Absorption (Emulsifiable) ointment bases: The term “absorption base” signifiesthe water-absorbing or emulsifying property of these bases and does not describe their action on the skin. They contain relatively less emollient properties than hydrocarbon bases. They are hydrophilic in nature and have a tendency to absorb large quantities of water and aqueous solutions. Such preparations normally do not contain water as a component of their basic formula, but if water is incorporated, it results in a water-in-oil (w/o) emulsion.
- Wool fat (Anhydrous lanolin): This is obtained from the wool of sheep as a purified anhydrous fat. It is practically insoluble in water but can absorb water up to 50% of its own weight. It is
used along with other bases in the preparation of a number of ointments. For example, simple
ointment I.P. contains 5% and eye ointment base B.P. contains 10% of wool fat.
- Hydrous wool fat (Lanolin):This is a mixture of 70% w/w of wool fat and 30% w/w of purified water. It is a w/o type of emulsion. Hence, aqueous liquids can be emulsified with it. Examples
are hydrous wool fat ointment B.P.C. and calamine coal tar ointment.
- Wool alcohol: This is an emulsifying fraction of wool fat. Wool alcohol is obtained by treating wool fat with alkali, with the separation of the fraction containing cholesterol and other alcohols. Normally, it contains not less than 30% of cholesterol. It is pharmaceutically employed as
an emulsifying agent and to improve texture, stability and emollient properties in the preparation of w/o emulsions and absorb water in ointment bases. For example, wool alcohol ointment B.P. contains 6% wool alcohol.
- Beeswax: This is obtained from the honey comb of bees as a purified wax, which is available as yellow beeswax and white beeswax. It is used in ointment preparations as a stiffening agent. For example, paraffin ointment B.P.C. contains beeswax.
- Cholesterol: Animals are the main source for cholesterol as it is extensively distributed in
them. Wool fat is also used as an alternative source of cholesterol. It is mainly used to increase the water-absorbing capacity of an ointment base. For example, hydrophilic petroleum U.S.P.
contains 3% cholesterol, 3% stearyl alcohol, 8% white beeswax and 86% white soft paraffin.
The following are the advantages of absorption bases:
- The base is easily spreadable and less occlusive in nature
- They assist in permeation of oil-soluble medicaments into the skin.
- They possess good emollient property.
- They are compatible with most of the medicaments.
- They are relatively thermostable or heat stable.
- They may be used in their anhydrous form or in an emulsified form.
- They absorb a large quantity of water or aqueous substances.
Water-miscible bases: These bases are miscible with large amounts of water. Ointments made from such bases are easily removable after use. The three anhydrous water-miscible ointment bases are as
- Emulsifying ointment B.P. (contains anionic emulsifier).
- Cetrimide emulsifying ointment B.P. (contains cationic emulsifier)
- Cetomacrogol emulsifying ointment B.P. (contains nonionic emulsifier)
An example of an ointment containing water-miscible base is compound benzoic acid ointment (Whitfield’s ointment), which is an antifungal ointment.
The following are the advantages of water-miscible bases:
- Ready miscibility with the exudates from lesions
- Reduced interference with normal skin function
- Good adherence to the skin because of their surfactant content
- Easy removal from the skin and hair
- High cosmetic acceptability
Water-soluble bases: These bases primarily consist of water-soluble ingredientssuch as polyethylene glycol (PEG), which are popularly known as “carbowaxes” and commercially known as “macrogols.”
Solids can be easily incorporated into these bases without much difficulty. Their water solubility promotes complete removal from the skin. Water-soluble bases are a range of compounds with the general formula CH2OH(CH2OCH2)nCH2OH. The PEGs are mixtures of polycondensation products of ethylene oxide and water and are exemplified by numbers representing their average molecular weights. They vary in consistency from viscous liquids to waxy solids. For example,
macrogols 200, 300, and 400 are viscous liquids, macrogols 1500 are greasy semisolids and macrogols 3000, 4000, and 6000 are waxy solids. Different grades of PEGs are mixed to get an ointment of desired consistency.
The advantages of PEGs as ointment bases are as follows:
- They are readily water soluble and, hence, are freely miscible with tissue exudates; they can be
easily removed from the skin.
- They promote good percutaneous absorption.
- They possess good solvent properties. Some water-soluble dermatological drugs such as salicylic acid, sulphonamides and sulphur are easily soluble in this base.
- They are nongreasy with good aging property.
- They neither hydrolysed nor undergo rancidity and hardly support microbial growth.
- They are compatible with many dermatological medicaments.
- They can be sterilized by heat and, hence, are preferred for ophthalmic ointments.
The following are their disadvantages:
- Packaging in plastic containers is difficult due to its remarkable solvent property.
- There is a reduction in the potency of activity of certain antibacterial agents, such as phenols,
hydroxybenzoates and quaternary compounds, when used in PEGs bases.
Methods of Manufacture of Ointments
The following are the various methods of manufacturing ointments:
- Fusion method
- Trituration method
- Chemical reaction method
- Emulsification method
This method is applicable to melt multiple ingredients, especially when an ointment base contains a number of solid ingredients such as white beeswax, cetyl alcohol, stearyl alcohol, stearic acid, and hard paraffin. The components of the formula are melted in the decreasing order of their melting point in the grated form. That is, the substance with the highest melting point should be melted first
followed by the substance with the next-highest melting point and so on. The medicament is added slowly into the melted base with intense stirring until the mass cools down and a homogeneous product is formed at the room temperature.
This method is applicable for the preparation of most of the medicated ointments containing insoluble drug substances. Finely powdered solids are passed through sieve #85. The medicament is taken on an
ointment slab and triturated lightly with a small amount of the base. A steel spatula with long, broad blade is used for this purpose. To this, additional quantities of the base are incorporated and triturated until the medicament is fully mixed with the base. Finally, liquid ingredients are incorporated to this semisolid mass.
Chemical Reaction Method
Several famous ointments of the past were prepared by chemical reactions. An example is the strong iodine ointment B. Vet. C. (British Veterinary Pharmacopoeia), which is used to treat ringworm in cattle. It contains free iodine. Earlier, these types of ointments were used as counterirritants in the treatment of human rheumatic diseases. A limitation is that these ointments stain the skin with a deep red color. The water dries up due to improper storage and the iodine crystals irritate the skin. Hence,
instead of water, glycerol is sometimes added to dissolve the iodine–potassium iodide complex.
Strong iodine ointment B. Vet. C.
Yellow soft paraffin
Dissolve iodine in aqueous potassium iodide solution. Melt the wool fat and yellow soft paraffin together and maintain the temperature to about 40°C. Slowly add iodine solution with stirring and continue until room temperature attained. The product is stored in a wide-mouthed amber-coloured glass jar. It is used to treat ringworm in cattle.
Alternative method of preparation: Iodine is effectively reacted with unsaturated jelly acids of the fixed oils. The free iodine gets complexed with the double bonds of the unsaturated constituents.
Oleic acid (unsaturated fatty acid) Diiodostearic acid (saturated fatty acid)
Nonstaining iodine ointment B.P.C. 1968
Yellow soft paraffin
Iodine is finely powdered in a glass mortar and the required amount is added to a glass-stoppered
conical flask containing arachis oil and stirred well. The mixture is cautiously heated at 50°C in a water bath in a closed condition, preventing the sublimation of iodine. Heating is continued until the initial brown color is changed to greenish-black, which concludes the chemical reaction process.
From this preparation, 0.1g of the substance is weighed and the amount of iodine is determined by B.P.C. method. The amount of soft paraffin base is calculated suitably to give the product the required strength. Soft paraffin is warmed to 40°C. The iodized oil is added and mixed well. The final preparation is packed in a warm, wide-mouthed, and amber-coloured glass bottle. It should be allowed to cool without further stirring.
An emulsion system contains an oily phase, an aqueous phase, and an emulsifying agent, complying with the basic requirements for the formation of a stable emulsion. For oil-in-water (o/w) emulsion systems, the following emulsifying agents are used:
- Water-soluble soap
- Cetyl alcohol
- Glyceryl monostearate
- Combination of emulsifiers, for example: triethanolamine stearate and cetyl alcohol
- Nonionic emulsifiers, for example: glyceryl monostearate, glyceryl monooelate, propylene glycol stearate
For w/o emulsion system, the following emulsifiers are used:
- Polyvalent ions, for example: magnesium, calcium, and aluminium
- Combination of emulsifiers, for example: beeswax and divalent calcium ion
Evaluation Tests for Ointments
The formulated ointments should be subjected to the following evaluation tests before being considered for the batch process.
- Penetration test: This test is carried out by the following methods:
(a) A weighed quantity of ointment under test is rubbed on a particular area of skin. After a
particulate time period, the ointment is scrapped and weighed. The difference between the initial and final weights will give the rate of penetration of ointment. However, this is a crude method and the results obtained may not be reproducible.
(b) It can be tested by using a semipermeable cellulose membrane as diffusion membrane.
(c) The Keshery–Chien cell or Franz diffusion cell method is a widely used in vitro instrument for the study of drug penetration. The diffusion membrane used can be a synthetic semipermeable membrane, animal skin membrane or cadaver skin. The study simulates the physiological conditions of human and the results obtained are reproducible.
(d) The cup plate method is also used. If the ointment contains any antimicrobial substance, then 2% w/v agar culture media with susceptible microorganism is taken in a petri dish. Bores are made and a preweighed sample of the ointment is introduced aseptically and incubated at 37°C. At frequent intervals of time, the petri dish is taken out and the zone of inhibition is measured, using which the rate of penetration can be calculated.
- Absorption of a drug: This test is performed for diadermic ointments (systemic circulation).A weighed quantity of ointment is applied to the skin (or mucous membrane). At frequent intervals of times, either the blood or the urine samples are collected and analyzed for drug content, from which the rate of absorption of drug is estimated.
- Test for sensitivity or irritability: A known amount of ointment is applied to the skin of a rabbit or human and checked for any lesions, patches, redness or any other allergic manifestations for a period of 2–3 weeks. The ointment passes the test if it does not produce any allergy or sensitivity.
Poultice, which is also known as cataplasms, is a soft, viscous, and wet or moist mass to be heated and medicated. This has to be spread on cloth over the skin for the treatment of an aching, inflamed, or painful part of the body. It can be used on wounds such as cuts. It can also be a porous solid filled with solvent used to remove stains from porous stones such as marble or granite.
The word “poultice” comes from the Latin puls or pultes, meaning “porridge.”
Many ready-made commercial poultices are also available. Some of these may be labelled as “drawing salves.” Poultices may also be heated and placed on an area where extra circulation is desired.
Types of Poultice for Boils
- Bran poultice: It is useful to reduce inflammations in boils. The poultice consists of mixing of bran with hot water and applying it on the boil head warm to the extent of tolerance.
- Bread and milk: It is used to develop heads in pus-filled boils so that the pus can easily flowout from the boil leading it to dry up soon. Bread soaked with milk is smashed and then applied on the head as poultice.
- Cabbage poultice: This poultice consists of a paste made by smashing raw or cooked cabbage.
A thick coating of the cabbage poultice on a boil is to be covered with a warm towel. This poultice is highly effective as a detoxification agent and is to be applied for 10 minutes at a stretch.
- Carrot poultice: It is highly beneficial for acne, cysts, and boils. The poultice is made up of boiled carrot. The carrot is first boiled until it becomes soft and then turned into a pulp. The pulp of the carrot is then applied on the boil head to allow the pus to flow out.
- Clay poultice: It is a very effective way to get rid of inflammations that are related to the development of boils. The clay is at first cleaned by removing impurities and then is converted into a paste by adding water or cider vinegar (Kaolin Poultice B.P.C.).
Creams are homogeneous, semisolid preparations consisting of opaque emulsion systems. Their consistency and rheological properties depend on the type of emulsion, either w/o or o/w, and on the nature of the solids in the internal phase. Creams are intended for application to the skin or certain
mucous membranes for protective, therapeutic or prophylactic purposes, especially where an occlusive effect is not necessary. The term “cream” is most frequently used to describe soft, cosmetically
acceptable types of preparations.
Definition: Pharmaceutical creams are semisolid preparations containing one or more active agents dissolved or dispersed in either a w/o emulsion or an o/w emulsion or in other types of water-washable base. Creams find primary application in topical skin products and are also used rectally and vaginally.
Advantages of Creams
- They promote prolonged contact at the site of application than any other semisolid dosage forms.
- They are nonsticky in nature and are easily washable.
- Creams can dry the injured area quickly than any other semisolid preparations.
- They have distinct three-dimensional thixotropic properties.
- They are no irritating on application to the skin.
- They are not expensive.
Disadvantages of Creams
- They are less hydrophobic than other semisolid preparation; hence, the risk of contamination is
- They are less viscous than other semisolid preparations.
Criteria of a Good Quality Cream
- It should have high affectivity.
- It should show rapid onset of action.
- It should be biocompatible and biomiscible.
- It should be free from grittiness.
- It should be smooth.
- It should be readily washable.
- It should be non-irritant.
- It should be nonallergic.
- It should be nontoxic.
- It should be physically and chemically stable.
Classification of Creams
- Cleansing creams: These are semisolid o/w emulsion preparations containing mineral oil,
which imparts cleansing action.
- Cold creams: These are semisolid w/o emulsion preparations; when applied to the skin surface,water gets evaporated and phase inversion occurs.
- Foundation creams: The main ingredient of these creams is humectants such as lanolin and mineral oil, which help in forming an invisible film.
- Night and massaging creams: These creams prevent drying of the skin by providing nourish-ment and proteins.
- Vanishing creams: These are o/w semisolid emulsions.
- All-purpose creams: These are for outdoor purposes and are more oily preparations.
Cold cream is a semisolid white w/o emulsion prepared with cetyl ester wax, white bees wax, mineral oil, sodium borate, and purified water. Sodium borate combines with the free unsaturated fatty acids present in the waxes to form sodium salts of fatty acids (soaps), which act as emulsifiers.
Cold cream is employed as an emollient and ointment base. For example, eucerin cream is a w/o emulsion ofpetrolatum, mineral oil, mineral wax, wool wax, alcohol, and bronopol. It contains urea as an active ingredient and is used to help rehydrate dry and scaly skin.
W/o emulsion base formula
White wax 12%
Cetyl ester max 12%
Mineral oil 56%
Sodium borate 0.5%
Purified water 19%
White bees wax 15.5%
Cetyl ester wax 6.05%
Mineral oil 42.5%
Sodium borate 1%
Vanishing creams are also called as stearate creams. Chemically, they are o/w emulsions consisting of a stearic acid, an alkali, a polyol and water. The alkali forms a soap with stearic acid, forming an in situ emulgent during the preparation, thereby producing a stable emulsion. The polyol (e.g., glycerin) makes the cream more spreadable and acts as a humectant to prevent the cream from drying out and cracking during storage in its container. Packaging the cream in an airtight screw-top jar or collapsible tube is also important in maintaining its water content. The product is noted for its smooth, dry feel
on the skin and its pearly appearance.
Earlier, carbonates or bicarbonates were used as the alkali. These release carbon dioxide during the production process, resulting in a foamy consistency. Some of the carbon dioxide will quickly escape, but small bubbles will remain and rise to the top of the mixture causing the cream to sink. Using hydroxides as the alkali avoided this problem and potassium hydroxide became a favourite in many formulations.
O/w emulsion formula (vanishing creams)
Differences between Cold and Vanishing Creams
Cold Cream Vanishing Cream
- It is a w/o semisolid emulsion. It is an o/w semisolid emulsion.
- It is meant for cleansing, massaging and
It is used as a foundation cream before applying
- It is more oily and greasy in nature. It is less greasy and oily in nature.
- It is not readily washable by water. It is readily soluble in water.
- There is no need for preservatives. It requires preservatives.
- It gives a cooling sensation. It leaves an immiscible layer.
- It does not show any pearliness, lustre,
It shows pearliness, lustre, and shine, because
stearic acid crystals shine on incidence of light.
- It is nonocclusive. It is semiocclusive.
- Humectants are not used. Humectants are added.
Table 7.6 Differences between an Ointment and a Cream
- Ointment bases are highly hydrophobic and
so they are sticky in nature.
Cream is not so sticky
- It is not readily washable as it is sticky and
greasy in nature.
It is readily washable.
- It does not show prolonged contact at the site
It shows prolonged contact at the site of action.
- Injured area dries slowly by ointment. Injured area dries quickly by creams.
Evaluation Tests for Creams
As creams are widely used for various body parts, general tests such as qualitative and quantitative
tests should be done.
- Viscosity: Measurement of viscosity of creams during manufacturing process determines the quality of the product. Viscosity of creams is non-Newtonian in nature; so, it should remain
constant during its shelf life. It can be determined using “Brookfield viscometer.”
- Patch test or sensitivity test: The sensitivity test for the final formulated cream should be done after application to the different parts of skin surfaces. It should be observed for any skin rashes, itching, irritation, or redness for a period of 7–14 days.
- Biological testing: This test is mainly performed for products containing hormones, vitamin preparations, and antiseptics.
- Cooling time and total stirring time: These two factors are used to determine the consistency, stability and viscosity of creams.
- Peroxide stability test in creams: In this test, 1g of cream is taken in a test tube and subjected to heating at a constant temperature of 95°C for 24 h. Care should be taken to ensure that the water level in the bath meets the upper surface of the cream in the test tube. Then, the contents in the test tube are emptied into an 250ml volumetric flask and subjected to peroxide content
determination by using the formula
Percentage stability = (Final H2O2 concentration/Initial H2O2 concentration) × 100
The stability of the peroxide cream should be more than 95%.
CONSIDERATION POINTS FORBDOSAGE FORM BEFORW PREPARATION AND CRITERIA FOR CLASSIFICATION.
Before we look on the consideration points for dosage form before preparation we have to define the following concepts :
Classification: refers to systematic arrangement of pharmaceutical preparation into various groups so as to make it easy to study, remember, recognize and identify them.
Pharmaceutical preparations: refers to various pharmaceutical products processed in pharmacy into various pharmaceutical dosage form.
Pharmaceutical products: refers to drugs of various pharmaceutical drugs, medicines and all special instruments available exclusively at the pharmacy.
Pharmaceutical Dosage form: refers to the final form at which a prescribed drug can be administered.
On the other hand, drug refers to a therapeutic substance either in a prepared or in unprepared state while
Medicine refers to the final prepared dosage form.
criteria for classifications: refers to the standard methods of carrying out classification of dosage forms.
These techniques include the following:
1.Classifcation according to method of preparation: The criteria further divide dosage forms into two:
a.] Galenical classifications; are preparations that were introduced and named after Claudius Galena and generally defined as the system of drug preparation that involves extraction processes, such as;
- Maceration; it is the extraction process by which a plant substance is placed inside into a container containing solvents and is allowed to stand for about 7 days then finally filtered to obtain the active pharmaceutical product in the solution.
- Decoction; is an extraction process by which any plant substance is boiled in a solvent for specified period of time and temperature.
- Percolation; is the extraction process that involves the use of an instrument known as a percolator.
- Digestion; refers to maceration extraction process by which heat is introduced below the container.
- Infusion; this extraction process by inserting the finely chopped plant into boiled water.
b.] Non-galenical classification refers to that group of pharmaceutical dosage forms that are prepared by any other method that is available other than extraction process.
- Classification basing on the route of administration. These are on the basis at which drugs enter into the human body:
Oral route; taken in through the mouth.
Topical route; are those dosage forms that are applied to the skin
Nasal route; are the dosage forms inhaled through nose
Rectal / vaginal route; are those that are administered via the anus or vagina in females.
Parenteral [intramuscular, subcutaneous, intravenous and intradermal injections are its types.
- Classification basing on the physical state: this is where dosage forms are grouped on the basis of either of the following;
Semi liquid or
4.classification on the basis of physio chemical structure; this groups the drugs into;
solutions; refers to that which have a solute completely dissolved in solvent.
Dispersion; refers to that which contain lesser solute suspended in a vehicle.
Emulsions; refers to that which contains two immiscible liquids.
Suspension; refers to the one with completely insoluble particle suspended in vehicle.
Micro-emulsions; that emulsion with very small globules.
Micro-suspensions; those that are almost forming homogenous solution.
- High-technology classifications: these are classification done basing on the new technology: they are classified basing on their biological actions, convection or drug’s delivery system.
- Classification based on sterility; this criterion is divided into;
A.] sterile preparations that imply all those dosage forms that are free from living micro-organisms, their dead bodies and free from any other substance other than the intended drug constituents.
B.] Non sterile Preparations refers to the group of impure dosage forms that therapeutic value would otherwise be compromised.
Having seen the above possible criteria of classification, we are going to focus on factors that enable us to classify pharmaceutical products to various classes as shown above.
Main descriptions about formulation considerations:
- Physical character of the API: this consideration point defines the general appearance of the drug basing on the physical properties and parameters such as, melting points, porosity, viscosity, density, compatibility, packing of powders, dimensions, particle size, shape, taste, color and aroma are the major consideration regarded while undertaking classification of various dosage forms. Various drugs have different set of the above parameters hence allow various groups into which dosage forms can be grouped into.
- Physiochemical properties: this is a factor of consideration that involves classification basing on observation on how drugs react with the environment. Before any classification we need to consider on the following;
o On either our drugs are Amorphous or crystalline in nature; amorphous drugs are those that are deprive of water of crystallization.
o Amorphous products normally on coming into contact with water it forms crystalline hence changing the chemical properties of the active pharmaceutical ingredient, thus very necessary to make proper considerations;
o We consider pH of the drugs. Various drugs have different levels of alkalinity or basicity hence proper considerations should be taken when classifying.
- Ionization ability of the drug; various parts of the body have different ionization potential hence affecting the rate at which the drug crosses into the section of action;
4.Solubility of the dosage form in dosage water and in the organic solvent; we have to consider the rate at which the drug dissolve in water or in organic solvents. Some drugs are;
Some drugs are soluble in water
Other drugs are soluble in organic solvents
Some drugs are immiscible on both hence forming emulsions such as oil in water or water in oil.
5.Permeability; various drugs have different rate of dissolution in the body hence the dosages form should be designed with the concept of appropriate mechanism of administering.
- Pharmacokinetics; this is scientific study of how drugs are absorbed, distributed, metabolized and finally excreted in the human body.
These considerations should be done on people of different age, gender, route of administration and means of application for the topical forms so as to come up with appropriate drug dosage form.
- Stability of the drugs; This consideration states that the drug constituents must be very remain the same with the same therapeutic value until its expiry, furthermore, we consider;
Physical stability. It is expected that when a drug is subjected to fragmentation or sizes, the therapeutic action should be constant.
Chemical stability. It is mandatory for drugs to retain their chemical nature despite of the changes in the physical properties such as when a tablet is split into two, each tablet should equally contain similar constituents.
Biological stability. Drugs have to be protected against attack by micro-organisms that would otherwise cause deterioration.
A drug should be therapeutic stability where their action should be constant from the first drug to the last drug in a given dose.
Drug toxicity should be identified and how to counter the toxicity nature of the drug.
- Flowability; this refers to the ability of the drug to flow. Highly density particles cannot freely flow whereas some flows easily, hence, flowing ability of a drug is useful in classifying the drugs.