A complete Liquid Dosage Form Notes | B pharm



The liquid form of a drug dose for administration or consumption. Route of administration may be oral, intravenous, intramuscular, cutaneous, subcutaneous, etc.

 Advantages of Liquid Dosage Form

  1. Most suitable dosage form for patients who have difficulty taking tablets or capsules, as might be the case with pediatric or geriatric patients.
  2. Attractive in appearance gives beneficial psychological effects.
  3. Drugs with bitter unpleasant taste can be given in sweetened, colored, flavored vehicles.
  4. Measuring flexibility as needed.
  5. If given orally, the liquid dosage is rapidly absorbed than tablets and capsules.
  6. Hygroscopic and deliquescent medicaments can easily be given in liquid dosage form.
  7. Products like adsorbents and antacids are more effective in this form.
  8. The liquid dosage form is expected for products like cough medicaments.

Disadvantages of Liquid Dosage Form

  1. Liquid dosage forms are usually more susceptible to chemical degradation when compared to solid dosage forms.
  2. Inconvenient to transport and store.
  3. Accidental breakage of the container results in loss of whole dosage form.
  4. The shelf-life of a liquid dosage form is often much shorter than that of solid preparation due to low stability.
  5. A solution often provides suitable media for microbial growth.
  6. Liquid dosage forms e.g. vaccines may require special storage conditions
  7. The taste of a drug that is usually unpleasant is more prominent in solution form.
  8. There is a higher chance of dose variability since the delivery of the dose depends upon the patient measuring the proper volume. This can be a significant issue for patients with vision-impaired, arthritis, unable to read the numbers on measuring cups.

Excipients used in formulation-

  1. Vehicles= vehicles are major components used as a base in which drugs and other excipients are dissolved or dispersed.
  2. Aqueous– (e.g. Water, polyhydric alcohols, hydro-alcoholic solutions, and buffers)
  3. Oily– (e.g. Vegetable or mineral oils, organic oily bases, emulsified bases, etc.),
  4. Buffers= Buffers are added to regulate the pH when an acid or alkali is added to the liquid dosage form. (e.g. Monobasic sodium acetate, sodium citrate, potassium phosphate, etc)
  5. Tonicity modifier= to make the solution iso-osmotic with tissue fluid to avoid pain and irritation (e.g. dextrose, NaCl)
  6. Preservatives= preservatives are added for fungistatic action to avoid microbial growth in the formulation. (E.g. benzoic acid, sod. Benzoate, alcohol, propylparaben, methylparaben)
  7. Antioxidant= Antioxidants are used to prevent oxidation which may lead to unpleasant taste, odor, taste, precipitation, discoloration, or even loss of activity. (E.g. sod. Sulfite, sod. Bisulfite, ascorbic acid, citric acid)
  8. Viscosity modifier= Used to minimize interparticle attraction and aggregation by functioning as energy barrier thus retarding particle settling. (e.g.  methylcellulose, microcrystalline cellulose, carboxymethylcellulose, etc)
  9. Sweetening agent= Used to mask the bitter taste of the formulation (e.g. sucrose, sorbitol, mannitol, glycerol)
  10. Flavors & perfumes = Used to give a specific flavor to improve patient compatibility. (e.g. cinnamon oil, lemon oil, peppermint oil)
  11. Colours= Used to improve the attractiveness of the product and easy identification of the formulation. (e.g. Amaranth sol.-RED, tartrazine sol.- YELLOW,)


Solubility enhancement Techniques:-

Strongly ionized drugs are freely soluble in water over a wide pH range, for unionized drugs/weak electrolytes at pH that are unfavorable for extensive ionization some techniques can be used to improve aq. Solubility,

  1. Cosolvency = Solubility of poorly soluble drugs can be improved by using cosolvents, cosolvents are a mixture of water and one or more water-miscible solvents.
  2. pH control= The solubility of the weak base can be increased by lowering pH & the solubility of a weak acid is increased by increasing pH.
  3. Solubilization=By addition of surface-active agents micelle is formed. Non-polar molecules will dissolve in lipophilic moiety and hydrophilic surfactant HLB value above 15 is valuable as solubilizing agents.
  4. Hydrotropy= Addition of large amt. of a second solute increase aq. Solubility of existing solute.
  5. Particle size reduction=As a particle size is reduced using micronization technique the surface area increases and that allows greater interaction with a solvent which causes increase insolubility.
  6. Nanonization= It improves the dissolution and bioavailability of numerous drugs which are poorly soluble in water. The technique used is wet milling, homogenization, spray drying, etc.
  7. Solid dispersion= It increases dissolution, absorption & therapeutic efficacy of a drug. Solid dispersion is a group of solid products consisting of at least 2 diffs. components as hydrophilic matrix and hydrophobic drugs.
  8. Complexation= Complexation of drugs with cyclodextrins has been used to enhance aq. Solubility and drug stability. It relies on relatively weak forces such as London forces, hydrogen bonding & hydrophobic interactions.

Pharmaceutical Calculations Notes