Download parenteral routes of administration

PARENTERAL ROUTES OF ADMINISTRATION
The three primary routes of parental administration
1. IV
2. IM
3. SC
*Elimination is always the same rate; it is dependent on the drug and not the route of administration
* Consider plasma drug concentration profiles for IV, IM, and SC: elimination portion of the curves are parallel
Secondary routes of parental administration
 Intracutaneous
 Intradermal
 Intra-thecal
 Peridural
 Intra-cisternal
 Intra-articular
 Intra-synovial
 Intra-arterial
 Intra-cardial
 Intra-peritoneal
 Intra-ocular
 Intrapleural
 Intraventricular: lateral ventricles of brain
Advantages of parental route over oral route
 Rapid action
 Entire dose is bioavailable
 Bypasses first pass metabolism
 Can give irritating drugs IV: avoide GI irritation
 Predictable blood concentration
 May give smaller doses
 Can treat difficult patients (e.g. nausea and vomiting)
Disadvantages of parental route
 Once injected, there is no retreat (recourse)
 Rapid action does not allow for antidote to be given
 More expensive $$$
 Difficult to administer or requires trained personnel to administer
 Requires sterile equipment and aseptic techniques
 Increases risk of infection
 Need to puncture patient (↓ compliance)
Physico-chemical factors affecting drug absorption by an extravascular route (e.g. IM)
 Drug solubility: if more soluble in oil, then slower absorption in the body
 Drug osmolarity or osmolality: needs to be isotonic; if hypertonic then slow absorption, if hypotonic then fast
 Partition coefficient: lipophilicity, solubility in oil vs. water
 Degree of ionization: when pH=pKa, then 50% of the drug is unionized, so 50% of drug is absorbed
 Binding to macromolecules: if bound to proteins, then drug cannot be absorbed
 Volume of injection: the smaller the volume, the quicker the absorption
 Physical form of the drug: solution, solid tablet, or implantable rod

Concentration gradient: the higher, the better; constant tonicity
Physiological factors affecting drug absorption by an extravascular route
 Muscle movement
 Body temperature
 Anatomical site: muscle vs. fat tissue
 Disease states: CV disease has impaired circulation, kidney disease has impaired excretion
 Tissue conditions: e.g. scar tissue from insulin injection, high fat tissue, etc.
 Presence of vasoactive agents: e.g. epinephrine & steroids cause vasoconstriction
 Presence of enzyme mediators: hyaluronidase makes hyaline tissue more porous, opens up fissure more
 Patient age: affects drug absorption, decrease in fatty tissue and muscle mass
Common diluents used to reconstitute powder drugs
 SWFI: sterile water for injection
 Sterile N.S.
 Bacteriostatic water for injection
 Bacteriostatic N.S. for injection
Commonly used IV fluids
 N.S.
 D5W
 D5/N.S.
 D5/0.45% N.S.
 D5/0.2% N.S.