Parenteral Drug Absorption and Formulation Quiz

Factors Affecting Drug Absorption and Formulation for Parenteral Products

• Intravascular injection results in immediate drug availability without absorption.
• For all other routes, drug absorption requires permeation of at least one blood vessel and tissue cell wall.
• Passive diffusion is the most common method of absorption for non-vascular injections.
• Factors affecting absorption include blood vessel size, exercise of injected tissue, and physical and chemical properties of the drug and dosage form.
• A drug's physiologic effect is influenced by its distribution, plasma protein binding, and rate of elimination.
• Intravenous and intraspinal preparations are typically aqueous solutions due to the risk of capillary blockage and nerve tissue sensitivity.
• Preparations for intramuscular, subcutaneous, and intradermal injections can be solutions, suspensions, or emulsions.
• Solid pellets may also be implanted subcutaneously or intramuscularly.
• The formulation of parenteral products must be carefully integrated with intended administration to a patient.
• Chemical and physical properties of a drug must be determined, and stability must be studied at each step of the process.
• Ophthalmic preparations require similar standards to those for internal body cavity injections due to the sensitivity of eye tissues.
• Irrigating solutions also require high standards as they can enter the bloodstream directly during a procedure.

Additionally, the intended route of administration affects the volume and isotonicity of the drug, with smaller volumes typically used for intracutaneous injections and larger volumes for IV injections with careful administration control.

Effects of Route of Administration on Parenteral Product Formulation

• The intended route of administration affects the formulation of a parenteral product.
• Intracutaneous injections use a volume of 0.2 ml or less due to small tissue volume and slow absorption.
• Subcutaneous injections use volumes of 1 ml or less, while intramuscular injections use volumes of 2 ml or less.
• Intraspinally, volumes of 10 ml or less may be given, but large volumes are safe only by the IV route with careful administration control.
• Intravenous administration is suitable for volumes greater than 20 ml, whereas infusion units are practical for 250 ml or more.
• Isotonicity is crucial for intraspinal injections due to slow cerebrospinal fluid circulation, while nonisotonic solutions may cause false signs of irritation in intracutaneous injections.
• SC and IM injections do not require isotonicity for comfort.
• Slightly hypertonic solutions given IM can increase drug absorption rate by causing local effusion of tissue fluids.
• IV fluids should be isotonic, but slow administration of a paratonic solution is safe with rapid dilution with blood.
• Only solutions of drugs in water are safe for intravenous administration; suspensions may cause blockage of small blood vessels.
• Muscle tissue tolerates oils and suspended particles well, making it the only route suitable for their administration.
• Formulation modifications can retard the rate of drug release from a depot by utilizing various esters or salts to produce stable suspensions.