Pharmaceutical aids: Organoleptic agents (Colouring, flavouring, and sweetening), Preservatives: Definition, types with examples and uses

Pharmaceutical Aids

Pharmaceutical aids are therapeutically inactive ingredients in the pharmaceutical formulations form added for pharmaceutical purposes. Pharmaceutical aids are also called excipients, or additives or adjuvants. They are used in pharmaceutical formulations (dosage forms) for any one of the following purposes

• To deliver medications to the body in a controlled and efficient manner.

• To ensure they are convenient for the administration

• To improve the stability, taste, preservation, appearance, bioavailability, and overall performance of the dosage forms.

Examples of pharmaceutical aids are preservatives, coloring agents, flavoring agents, sweetening agents, binders, fillers, disintegrants, and etc.

Preservatives

Preservatives are added in the pharmaceutical formulation to prevent or stop the growth of microorganisms throughout the shelf life of the preparation. Normally liquid dosage form contains water and emulsifying agent or suspending agent. Some ingredients of the dosage forms (pharmaceutical formulation) support the microorganism growth. Thus these formulations require preservatives.

For example, Liquid dosage forms contain water and carbohydrate ingredients. They promote the growth of microorganisms. Multi-dose injectable containers require preservatives. Microorganisms may enter into multi-dose containers during the withdrawal of the drug. Preservatives in ophthalmic solution must be gentle and well tolerated because eye tissues are very delicate.

Preservatives are essential in the formulation for the following purposes

• i. Microbial control

• ii. Prolong the shelf life of the formulation

• iii. Patient safety.

The most common preservatives for pharmaceutical preparations are

• Alcohol 15 to 20%

• Benzalkonium chloride 0.004 to o.o2%,

• Chlorhexidine 0.,

• Methyl paraben and Propyl paraben 0.1 to 0.2%,

• Sodium benzoate and Benzoic acids 0.1 to 0.2%,

• Phenol 0.2 to 0.5%,

• Chlorocresol 0.05 to 0.1%,

• Scorbic acid 0.05 TO 0.2%,

• salicylic acid 0.1% , etc.

Not a single preservative is efficient enough to prevent the growth of microorganisms in pharmaceutical preparations. Thus, a combination of preservatives is used to prevent the growth of microorganisms.

Choice of preservatives: Preservatives should be carefully selected and used in appropriate concentration. This ensures the effectiveness of preservatives and minimizes adverse effects of the preservatives on the human body. The preservatives should have the following characteristics:

• i. Non-toxic

• ii. Free from odor and taste

• iii. Remain stable during the shelf life of the drug,

• iv. Effective against a wide range of microorganisms,

• v. Compatible with other ingredients of the formulation

• vi. Soluble in the aqueous phase of the emulsion formulation.

Stabilizer: Stabilizer maintains the physical and chemical stability of the formulation during its shelf life period. They perform the following functions to improve the stability of the liquid formulation. They Prevent Chemical Degradation in the formulation during their shelf life such as oxidation, dehydration, photolysis, hydrolysis, etc. Among them, oxidation and decomposition under light are the most common.

Stabilizers act as antioxidants or chelating agents. Antioxidants have a great affinity with oxygen. They compete with formulation ingredients to combine with oxygen. All oxygen will be utilized by the antioxidant. This action of antioxidants protects formulation ingredients from oxidation.

Stabilizers should be colorless, non-toxic, non-irritant, thermostable, compatible with ingredients and packaging materials, and effective against a wide range of pH and temperature.

Some of the commonly used antioxidants are ascorbic acid, tocopherol, sodium metabisulphite, sodium bisulfate, sodium thiosulfate, etc. Sometimes combination of chelating agents and antioxidants is used as a stabilizer. This combination has a synergistic effect to protect the formulation from degradation. These properties inhibit chemical reactions and protect against formulation degradation.

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Organoleptic Agents

Organoleptic agents affect the sensory properties of a pharmaceutical formulation. These sensory properties include taste, smell, texture, and appearance. Organoleptic agents influence a patient's perception and acceptance of a product. They are carefully selected. They mask undesirable tastes or odors in the pharmaceutical formulations. They make medications more palatable and easier to administer. Three types of Organoleptic agents are used for pharmaceutical preparations. These are flavoring agents, coloring agents, and sweetening agents. 

1. Flavoring agents

Flavor is not just about taste. It is a combination of pleasant taste, aroma, temperature, texture, and visual sensation. Flavoring agents are volatile in nature with a prominent pleasant odor. Flavoring agents are used for the following purposes:

• i. Imparting pleasant odor

• ii. Masking unpleasant taste

• iii. Enhancing palatability

• iv. Improving user experience

Both natural and synthetic flavoring agents are available for pharmaceutical purposes. Generally, liquid dosage forms for oral administration are flavored with fruity or spicy flavoring agents. Liquid dosage forms for external application are flavored with a flowery flavoring agent.

Examples of flavoring agents are coffee, vanilla, chocolate, tolu balsam, malt extract, pineapple, cardamom, cinnamon, peppermint, menthol, volatile oil from clove, dill, lemon, orange, rose, etc. Synthetic chemicals such as certain alcohols, aldehydes, esters, fatty acids ketones, and lactones are also used as flavoring agents. They are preferred over natural flavoring agents due to the following reasons: Readily available, Economical, More stable, Constant composition, and Easy prediction of their incompatibility. Normally, A blend of flavoring agents is used to mask the odor and taste of liquid dosage forms.

Selection of flavoring agents:

• i. Cinnamon flavor followed by orange syrup, coca syrup, cherry syrup, and raspberry are suitable for the salty liquid dosage forms,

• ii. Coca syrup, raspberry syrup, and cherry syrup are used for bitter taste liquid dosage forms,

• iii. Raspberry and other fruit syrup are preferred to mask the sour taste of liquid dosage forms,

• iv. The oily taste of liquid dosage forms is masked by peppermint oil, wintergreen oil, malt extract, etc.

Flavoring agents are dissolved in a suitable solvent. Then it is added into preparation. Water is used to dissolve water-soluble flavoring agents. Poorly water-soluble flavoring agents are dissolved in alcohol or hydro-alcoholic solvent.

2. Sweetening agents

Sweetening agents are used in liquid dosage forms for oral administration. Sweetening agents perform the following functions

• i. Mask the unpleasant tastes such as bitter, sour, or/and other disagreeable tastes.

• ii. Enhance patient acceptance

• iii. Improve palatability

The commonly used sweetening agents for liquid dosage forms are sucrose, sorbitol, honey, maple syrup, and artificial sweeteners such as saccharine, aspartame, cyclamate, etc. Sorbitol, saccharine, and aspartame are sugar-free sweetening agents.

Sucrose is the most widely used sweetening agent. The simple syrup contains 66.7% w/v sucrose. Simple syrup is frequently used in liquid dosaGE GFORM. It is physically and chemically stable at pH 4 to 8. Saccharine is 300 times sweeter than sucrose. Saccharine sodium is used in toothpaste and other oral preparations for oral hygiene. It is preferred over sucrose because it does not cause dental carries. It is also used in foods for diabetics and weight-conscious persons. It is stable at pH 3 to 8.

 Sweetening agents and their concentration are selected carefully for product stability while providing a pleasant taste. Patients suffering from diabetes or on a restricted diet to control weight prefer sugar-free sweetening agents.

3. Coloring agent (Colorants)

Coloring agents are used to increase the organoleptic properties of the dosage forms (pharmaceutical products). In dosage forms, colorants serve the following purposes:

• i. Aesthetic appeal: Coloring agents are used as sensory adjuvant. It helps to increase product patient acceptability. It is especially helpful for pediatric patients and geriatric patients.

• ii. Masking unwanted color: Unwanted color develops in the preparation during their manufacturing or storage. This unwanted color is masked by using a flavoring agent. This improves the patient's confidence regarding preparation quality.

• iii. Identification: Colorants help to distinguish the formulation of different strengths of the same API.

• iv. Brand recognition: Sometimes colorants help to recognize a specific brand or specific manufacturer.

Types of colorants: The following are commonly used colorants for the liquid dosage forms

• i. Natural colorants: Sources of natural colorants are plants, animals, and minerals. Colorants obtained from minerals are also called pigments. They were used in cosmetics and preparations meant for external applications. But now they have been replaced by synthetic colorants. Examples are ferric oxide, titanium dioxide, carbon black, etc. Colorants from plants are chlorophyll, indigo, carotenoids, flavons, etc. Very colorants are from animal sources. Examples are carminic acid from the insect Coccus cacti cochineal. Natural colorants are not in use due to the easy availability of synthetic colorants.

• ii. Synthetic colorants: Coal tar is used to prepare synthetic colorants such as nitro-dyes, nitroso-dye, azo-dye, rosanilines, etc. Only colorants mentioned in the Drug and Cosmetic Acts 1940 are used in the pharmaceutical industry. Coloring agents should be used in appropriate concentration. Most colorants in dosage forms for internal administration retard the absorption of API inside GIT.

Alok Bains