Parenteral Formulations: Solutions Quiz

Solutions

• A solution is a homogeneous mixture with uniform composition throughout.
• Examples: salt-water solution, NaCl solution.
• A solution can contain more than one solute.
• Types of solutions:
  • Aqueous solution: water as solvent.
  • Non-aqueous solution: water is not the solvent.
  • Solid solution: solid as solvent.

Solubility

• Solubility is the ability of a solvent to dissolve a solute.
• Defined as the maximum amount of a substance that will dissolve in a given amount of solvent at a specified temperature.
• Solubility depends on various factors:
  • Solute-solvent interactions.
  • Temperature.
  • Pressure.
  • Polymorphic form of the solid.

Parenteral Formulations

• Introducing a drug into the body through a route other than the digestive system.
• Parenteral preparations:
  • Sterile, pyrogen-free liquids (e.g., solutions, emulsions, suspensions).
  • Solid dosage forms packaged in single-dose or multidose containers.
• Administered through the skin or mucus membranes into internal body compartments.

Rational and Advantages

• Rational: drug is not absorbed orally, unstable in GIT, or undergoes extensive first-pass metabolism.
• Advantages:
  • 100% drug bioavailability is possible.
  • Prolonged drug action is possible.
  • Correcting serious disturbances of fluid and electrolyte balances.
  • Supplying total nutritional requirements when food cannot be taken orally.
  • Patient compliance problems can be largely avoided.

Disadvantages

• Most inconvenient route of administration.
• Pain upon injection.
• Requires trained professional for administration.
• Higher chances of improper dosing, adverse effects, and blood clot formation.
• Expensive manufacturing and packaging requirements.

Parenteral Routes of Administration

• Common injections: IV, IM, SC.
• IV: directly into a patient's vein.
• IM: into the muscles.
• SC: just under the skin.
• Common injection sites: abdominal wall, thigh, deltoid area.

Requirements for Parenteral Formulations

• Sterility.
• Particulate material-free.
• Pyrogen-free.
• Stability.
• pH.
• Osmotic pressure.

pH Requirements

• Normally close to physiological pH (7.4).
• pH 2-12 can be tolerated for IV (SVP, rapid bolus).
• pH 3-11 for IM administration.
• pH 3-6 for SC administration.
• pH > 9 – necrosis.
• pH < 3 – pain, phlebitis.

Added Substances (Excipients)

• Added only if they increase stability or usefulness.
• Not harmless in the amounts administered.
• Do not interfere with the therapeutic efficacy of the preparation or with specified assays and tests.
• Examples: antibacterial preservatives, buffers, solubilizers, antioxidants.

Sterility

• Parenteral preparations must be sterile or free of microorganisms.
• Ensured through:
  • Aseptic techniques.
  • Special clothing (gowns, masks, hair net, gloves).
  • Laminar flow hoods placed in special rooms.

Sterilization

• Means destruction of all living organisms and their spores or their complete removal from the preparation.
• Methods:
  • Steam.
  • Dry heat.
  • Filtration.
  • Chemical sterilization.
  • Radiation (gamma radiation).

Osmolality and Osmolarity

• Osmolality: concentration as number of solute particles per kilogram of solvent.
• Osmolarity: concentration as number of solute particles per litre of solvent.
• Isosmotic: two solutions with the same number of solutes or osmolality.
• Isotonic: when a solution has the same salt concentration as the blood and cells of the human body.
• Hypertonic: higher solute concentration.
• Hypotonic: lower solute concentration.

Tonicity

• Refers to the ability of a solution to change the volume of a cell.
• Isotonic solution: does not change the volume of a cell.
• Hypotonic solution: causes a cell to swell.
• Hypertonic solution: causes a cell to shrink.
• Tonicity takes into consideration the ability of the solute to cross the cell membrane.

Test your knowledge about solutions, homogeneous mixtures, heterogeneous mixtures, solvents, and more in the context of parenteral formulations. Understand the concept of well-mixed compositions and differentiating between types of mixtures.