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Review Article | DOI: https://doi.org/10.31579/2639-4162/254
Department of Pharmaceutics, RBVRR Women’s college of Pharmacy, Hyderabad.
*Corresponding Author: A. Krishna Sailaja, Bayya Hrushitha, Department of Pharmaceutics, RBVRR Women’s college of Pharmacy, Hyderabad.
Citation: A. Krishna Sailaja, Bayya Hrushitha, Bandra Ausha, Chinthakunta Deepika Reddy, Kommireddy Tejaswini., (2025), Study of Natural Excipients in Liquid Dosage Forms, J. General Medicine and Clinical Practice, 8(3); DOI:10.31579/2639-4162/254
Copyright: © 2025, A. Krishna Sailaja. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Received: 07 February 2025 | Accepted: 21 February 2025 | Published: 28 February 2025
Keywords: sportswomen/female athletes; single combats; freestyle wrestling; classical wrestling; sexual somatotypes; masculinization
Liquid dosage forms can be administered by oral and parenteral (injectable, inhalation, ophthalmic, optical, nasal, and topical) routes. Oral liquids are nonsterile, whereas liquids administered by the parenteral route are both sterile and nonsterile mixtures. The liquid formulations may be provided as reconstitute powders or as ready-to-use liquids. This article describes manufacturing procedures, quality assurance and control, physicochemical parameters that affect liquid formulation characteristics, and regulatory requirements for the production of both sterile and nonsterile liquids.
Liquids are pourable dosage forms and can be solutions or dispersions. In contrast to liquid dispersions, which can be two-phase or multi-phase systems made up of one phase dispersed through another phase or phases, pharmaceutical solutions are transparent, uniform, single-phase systems that contain one or more drug ingredients dissolved in one or more solvents. Micelles (surfactant solutions), lipid vesicles (liposomes), solid particles (suspensions), and oil droplets (emulsions) can all make up the dispersed phase.
Figure 1: Liquid dosage forms
Advantages of liquid dosage forms
| Formulation | Description |
| Syrups | Syrups are concentrated, aqueous preparations of sugar or sugar substitutes intended for oral administration of bitter-tasting drug substances |
| Oral solutions | Oral solutions are liquid preparations intended for oral administration. Oral solutions contain one or more active substances and inactive excipients |
| Elixirs | Elixirs are clear, sweetened, hydroalcoholic (5@%) solutions intended for oral use. Nonmedicated elixirs are employed as vehicles for medicated elixirs. |
| Ophthalmic solutions | Ophthalmic liquid products are sterile preparations intended for application to the conjunctiva, conjunctival sac, or eyelids. |
| Nasal solutions | Most nasal solutions are administered as nasal drops or sprays for local and systemic purposes. |
| Enemas | Enemas are oily or aqueous solutions that are administered rectally. |
| Suspensions | Suspension is a liquid dosage form of poorly water-soluble drug(s) dispersed in a liquid medium |
| Emulsions | Emulsions are liquid disperse systems consisting of two immiscible phases, one of which is dispersed as globules in the other liquid phase.[37] |
Table: -1 Different types of dosage forms
SYRUPS: Syrups are concentrated, aqueous preparations of p0370 sugar or sugar substitutes intended for oral administration of bitter-tasting drug substances. Nonmedicated or flavoured vehicles (syrups) are syrups that contain flavouring compounds without the use of drugs. When making medicated syrups or impromptu compounding prescriptions, these syrups act as tasty carriers for medicinal ingredients that will be added later. The taste of pharmacological compounds is covered up by syrup carriers with the right amount of sweetness and viscosity.
Advantages of natural syrups:
| Flavours | Orange oil, Raspberry, Neroli oil, Peppermint oil |
| Antioxidant | Peppermint, Rosemary, Cinnamon, Saffron |
| Sweeteners | Honey, Sucrose, Glycyrrhizin, Hesperidin |
| Preservatives | Clove oil, Tea tree oil, Ginger oil |
| Colourants | Carminic acid, Tyrian purple, Alizarin, Indigo [39] |
Table 2: - Excipients Used in Syrups:
.Flavours: Flavors are those agents which are used for masking the taste and also hide the unpleasant taste or Oduor of a dosage form. Flavors enhance the likelihood of medicines and make them more compatible for administration to a patient. Use of flavors in dosage forms make children take medicines without any problem. Flavoring agents used in different dosage forms are tablets, pills, pellets, capsules, pastes, syrups, emulsions, suspensions, mouth washes etc. Natural flavoring agents give the realistic flavor with good oduor and have no negative effect on human as well as environment.
Ideal properties of natural flavoring agents:
| Excipient | BS | Family | Synonym | Use | Formulation |
| Orange oil | It comes from the rind of sweet orange fruit Citrus sinensis | Rutaceae | Citrus aurantium | Flavor | Emulsions |
| Raspberry | It is obtained from the fruits of Rubusrosi folius | Rosaceae | Cane fruit | Flavor | Syrups Suspensions Serums |
| Neroli oil | It is extracted from flowers of citrus aurantium var | Rutaceae | Citrus bigaradia oil | Perfume | Oils |
| Peppermint oil | It is obtained from the flowering parts and leaves of the peppermint plant | Lamiaceae | Menta pepperita | Perfume | Oil roll on [41] |
Table 3: - Details of various natural flavoring agents as excipients in liquid dosage forms
Sweetening Agent: Sweetening agents are chemical substances that are added to either mask the unpleasant taste or enhance the perception of a sweet taste in some oral pharmaceutical preparations such as tablets, syrup, suspension etc. Also, Sweetening agents are called sweeteners. Importantly, sweetening agents are the common excipients for paediatrics
Ideal properties of natural sweetening agent:
| Excipient | BS | Family | Synonym | Use | Formulation |
| Honey | It is a secretion deposited from the honey comb by the Apis mellifera | Apidae. | Madhu | Sweetening agent | Syrups |
| Sucrose | It is a ddisaccharide sugar obtained mainly from the cane juice of saccharum officinarum | Graminae | Beet sugar, cane sugar | Sweetening agent | Syrups, lozenges, Injections |
| Glycyrrhizin | It is a penta-cyclic triterpenoid saponins glycoside obtained from root, stolon of Glycyrrhiza glabra | Leguminosae | Liquorice | Sweetening agent
| Cough mixtures |
Table 3: - Details of various natural sweetening agents as excipients in liquid dosage forms
Colorants: Colorants or coloring agents are commonly used for imparting distinctive appearance to the pharmaceutical dosage form. Colorants are agents used in the pharmaceutical preparations like cosmetics to give aesthetic appearance to the dosage forms. Dosage forms that are colored are tablets (either the core itself or the external coating) hard or soft gelatin capsules (the capsule shell or coated beads) oral liquids, toothpastes, topical creams, ointments and salves.
Ideal properties of natural coloring agent:
It occurs as red crystals in pure state when recrystallized from light petroleum.[5]
| Excipient | BS | Color | Synonym | Use | Formulation |
| Carminic acid | It is obtained from insect Coccus cacti | Bright red | Carmin | Coloring agent | Emulsions |
| Tyrian purple | It occurs by air oxidation of Murex brandaris(snail) | Bluish purple | Royal purple | Coloring agent | Emulsions Oils |
| Alizarin | It comes from the roots of madder plant, Rubia tinctorum | Red | Mordent red 11 Turkey red | Coloring agent | Emulsions |
| Indigo | It comes from the leaves of Indigofera tinctoria plant | Dark blue | Coloring agent | Tinctures [44]
|
Table 4: - Details of various natural coloring agents as excipients in liquid dosage forms
Preservatives: Preservatives are usually used to minimize the shelf life of several food products and pharmaceuticals. Preservatives are vital to avoid the alteration and degradation of microorganisms during storage. Particularly in those with greater water content [6]
Ideal properties of natural Preservatives:
| Excipient | BS | Family | Synonym | Use | Formulation |
| Clove oil | Buds of myrtaceous syzygium | Myrataceae | Eugenol | Preservative | Mouthwashes Oils |
| Tea tree oil | Derived from the leaves of the melaleuce alternifolia plant | Myrtaceae | Melaleuca | Preservative | Essential oils |
| Ginger oil | It consists of dried rhizomes of Zingiber officinale | Zingiberacae | Zingiber | Preservative | Syrups[8] |
Table 5: - Details of various natural flavoring agents as excipients in liquid dosage forms
Suspensions: A liquid dosage form of a medicine or drugs that are poorly soluble in water and distributed in a liquid medium is called a suspension. Particles in an ideal suspension are evenly distributed and do not aggregate. Particles should be gently stirred to resuspend them even if sedimentation takes place. Aqueous suspensions are intended for oral, ophthalmic, inhalation, and topical applications, while oil-based suspensions have parenteral applications (e.g., sustained-release depot formulations). Oral and topical suspensions contain a high concentration of solids in the range of 5P% solid particles, while parenteral suspensions incorporate 0.5%% solid particles. Based on particle size, suspensions are classified as coarse or colloidal dispersions, with the former containing particles of mean diameter in the range of 125 μM, and the latter containing particles with a mean diameter less than 1 μM [7]
Flocculated suspension: n flocculated suspensions, the particles organise into loose aggregates that resemble networks. These suspensions exhibit a rapid rate of sedimentation, yet no hard cake forms because the particles are loosely packed. Re-dispersing such flocs is not difficult.
Deflocculated suspension: Deflocculated suspension: Suspensions consist of uniformly scattered particles in the aqueous phase. In deflocculated suspensions particles exist as separate entities and exhibit a slow rate of sedimentation. Sediments tend to form a hard cake which is difficult to re-disperse.
Advantages of natural suspensions:
1. Drug compounds that are insoluble in water can be made into suspensions.
2.they prolong drug release rates;
3. they reduce the rate at which hydrolytic drug molecules degrade; · medications with extremely poor solubility are effectively prepared as suspensions.
4. suspension for patients with swallowing difficulties can be formulated as palatable suspensions. Some of the disadvantages include (a) aggregation of particles; (b) complex manufacturing processes.[8]
| Wetting agent | Lecithin, Sorbitan monolaurate, Sorbitan monooleate, Ceto stearyl alcohol |
| Suspending agent | Kaolin, Sesame oil, Hectorite, Ceratonia |
| Preservatives | Clove oil, Neem oil, Ginger oil, Tea tree oil |
| Antioxidant | Peppermint, Rosemerry, Cinnamon, Saffron [9] |
Table 6: - Excipients used in suspensions:
Suspending Agent: A suspension is a colloidal dispersion in which a solid is dispersed in a continuous liquid phase. The continuous phase is frequently referred to as the exterior phase, and the scattered solid phase as the interior (disperse) phase. In a suspension, the solute particles are fairly large in size.
Ideal properties of natural suspending agent:
| Excipient | BS | Family | Synonym | Use | Formulation |
| Kaolin | Kaolin is a hydrated aluminum silicate obtained by mining naturally occurring mineral deposits | - | Argilla bolus alba China clay | suspending agent | mixtures |
| Sesame oil | Sesame oil is obtained from the ripe seeds of the sesamum indicum plant | Pedaliaceae | Benne oil, gingelly oil | suspending agent | solutions, emulsions, suspensions |
| Hectorite | Natural deposits it is further processed to remove grit and impurities | - | Astratone40 Bentone CT |
suspending agent | Creams lotions |
| Ceratonia | It is obtained from the ground endosperms from the seeds of the locust bean tree Ceratonia siliqua and belonging to the family Leguminosae | Leguminosae | Algaroba, | suspending agent |
Emulsions [41] |
Table 7: - Details of various natural suspending agents as excipients in liquid dosage forms
Antioxidant: Antioxidants are compounds that inhibit oxidation (usually occurring as autoxidation), a chemical reaction that can produce free radicals. Antioxidants are frequently added to industrial products, such as polymers, fuels, and lubricants, to extend their usable lifetime.
Ideal properties of natural anti-oxidants:
1.It should be stable
2.It should be effective in low concentration
3. It should be compatible
4.It should be non-toxic [11]
| Excipient | BS | Family | Synonym | Use | Formulation |
| Rosemary oil | Rosemary is obtained from the flowering tops of leafy twigs of Rosmarinus officinalis | Lamiaceae | Rosmarinus officinalis | antioxidant | Oils |
| Cinnamon | The Cinnamon consist of dried bark, freed from the outer cork and from the underlying parenchyma | Laureceae | Ceylon cinnamon, cinnamon bark | antioxidant | Gargles |
| Thyme oil | It is extracted from the flowering parts of the mint plant | Lamiaceae | Thymus vulgaris | antioxidant. | Mouth washes |
Table 8: - details of various natural antioxidants as excipients in liquid dosage forms
Emulsions: Emulsions are liquid disperse systems consisting of two immiscible phases, one of which is dispersed as globules in the other liquid phase [50]. The presence of an emulsifier stabilises the two phases of emulsions. While particle diameters as tiny as 0.01 μM and as large as 100 μM are possible, the dispersed phase's droplet diameter ranges from roughly 0.1 to 10 μM. are not uncommon. The consistency of emulsions ranges from that of a liquid (e.g., fat emulsions) to a semisolid (e.g., ointments and creams]
Advantages of emulsions:
• To solubilise hydrophobic or oil soluble drugs
• To enhance drug absorption through
• To improve medication absorption through topical application
• To cover up the unpleasant taste and smell of medications.
• To enhance palatability of nutrient oils [12]
| Antioxidant | Peppermint oil, Rosemary oil, Cinnamon oil,Thyme oil |
| Emulsifying agent | Cottonseed oil, Faba bean oil, Mustard oil, Palm oil |
| Preservatives | Clove oil,Neem oil, Cumin seeds, Cayenna pepper, Ginger oil, Tea tree oil [13] |
Table 9: -Excipients Used in Natural Emulsions:
Emulsifying Agent: Emulsions are liquid disperse systems consisting of two immiscible phases, one of which is dispersed as globules in the other liquid phase. While particle diameters as tiny as 0.01 μM and as high as 100 μM are not unusual, the dispersed phase's droplet diameter ranges from roughly 0.1 to 10 μM. While particle diameters as tiny as 0.01 μM and as high as 100 μM are not unusual, the dispersed phase's droplet diameter ranges from roughly 0.1 to 10 μM to a semisolid (e.g., ointments and creams]
Ideal properties of emulsifying agent:
| Excipient | BS | Family | Synonym | Use | Formulation |
| Cotton seed oil | It is obtained from the seed of cultivated varieties of Gossypium hirsutum linn | Malvaceae | Refined cotton seed oil | Emulsifying agent | oils |
| Faba bean protein | It comes from the Faba bean | Leguminoseae | Broad bean | Emulsifying agent | Gels |
| Mustard oil | It is obtained from the seeds of mustard plant | Brassicaceae | - | Emulsifying agent | Essential oils Creams |
| Palm oil | the oil obtained from the pulp of the fruit of the oil palm Elaeis guineensis jacq | Aceraceae | Cage soft Dynasan 60 | Emulsifying agent | Emulsions [15] |
Table 10: - Details Of Vari ous Natural Emulsifying Agents as Excipients In Liquid Dosage Forms
Conclusion:
Pharmaceutical excipients derived from natural sources have attracted a great attention in developing convectional dosage forms and novel drug delivery systems. The use of natural excipients is steadily increasing day by day due to the side effects of synthetic excipients. Hence natural excipients are being preffered over synthetic as they are cheap, biodegradable and enhance the bioavailability, stability, safety, efficacy and patient compliance. Therefore, there is going to be a great interest in natural excipients to obtain a better dosage form.
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