Appropriate excipients selection: Liquid dosage forms (oral)(a) Solutions (b) Suspension (c) Elixirs (d) Concentrates. -Better compliance in case of pediatric and geriatric patients. - No dissolution time -Faster absorption through stomach/intestine - Achievement of peak plasma rapidly. Various excipients employed in theseformulation are: vehicles, solubilizers, viscosity builders, preservatives, sweetness, colors and flavors, antioxidants. Challenges such as stability of drug solubility of drug at required level and an acceptable taste can be achieved with proper and judicious use of these excipients. Drugs physicochemical characterization such as solubility, pH stability, pKa values of reactive functional groups is essential in order to choose the proper excipients.
Aqueous: water, hydro-alcoholic, polyhydric alcohols, buffers. Oily: Vegetable oils, mineral oils, organic oily base or emulsified bases.
Solubilizers: Wetting agents, and surfactants, tweens, spans, poloxamers.
pH modifiers: buffering agents
Suspending agents and viscosity modifiers: sodium alginate, methyl cellulose, HPMC, Na-CMC, MCC, tragacanth, xanthum gums, bentonite, guar gum, colloidal silicone dioxide.
Preservatives: Phenol, chloro-cresol, alkyl esters of p-hydroxy benzoic acid, boric acid, sorbic acid and their respective salts, chlorobutanol, benzyl alcohol, beta-phenyl ethyl alcohol.
Stabilizers: alpha-tocopherol, acetate, ascorbic acid, BHT, monothioglycerol, sodium bisulfite, sodium sulfite, ascorbyl palmitate, cysteine, sodium thiosulfate, BHA, propyl gallate, sodium meta-bisufite, thiourea.
Excipients are considered as indispensable components of drug products. Mostly they remain in greater proportion in comparison to active pharmaceutical ingradien, as it forms the bulk of the formulation.
Excipients selection generally focused on the following desirable characteristics: Functionality, material consistency, regulatory acceptance cost, availability and sources. Material properties such as micomeritics, chemical, thermal, rheological, mechanical, etc. also play an important role in development of drug formulation.
Other factors such as physico-chemical properties, stability and compatibility, pharmacokinetic attributes, permeation characteristics, absorption behaviors,, drug delivery, intellectual property issues also matter while selecting an excipients.
The quality by design excipients help in studying excipients normal behaviours and their impact on the processes related with formulation development. Excipients stability test allows a formulator to determine drug-excipient interaction which can be either avoided or can be modified to utilize in an efficient manner which helps in minimizing the risk associated with the excipients. Excipients selection also depends on the route of administration.
Excipients used in solid oral dosage forms: Diluent, binders, adhesive, lubricant, glidant, disintegrants, super disintegrants, coloring agents, flavors, sweeteners,, sorbents, wetting materials, plasticizer.
Excipients are also used in aerosol formulation are known as propellant. Excipients used in semi-solid dosage forms are structure forming excipients, preservatives, antioxidants, solubilizers, gelling agents, emollients, suppository bases.
Therefore it may be concluded that excipients are indispensable part of the drug products, must be evaluated for their expected performance, safety and stability. Excipients may interact with the drug , with other excipients and also with packaging material which render them harmful. Therefore their safety and stability are tested by subjecting them to extreme conditions of temperature and humidity. If stability testing data favor the use of excipients in the formulation, they are further tested for assuring safety for humans or animal use. Many new excipients are introduced in the market along with co-processing techniques. Therefore it is important to test their use in various complex delivery systems, and as per IPEC norms new excipients utilised for human use need to be investigated to a thorough safety assessment