Principles and Methods of Drug Administration CHAPTER 3 -2 Dr. Dipa Brahmbhatt VMD MpH

Route of Administration Parenteral drugsParenteral drugs: ‘excluding the SI’route other than the GI tract: IV,IM,SQ Nonparenteral/oral: through GI tractLocally: Where action requires

Route of Administration DRUG FACTORS – Effect parenterally vs. nonparenterally – Water-insoluble drugs IM vs. IV – Stomach pH can destroy some drugs Solubility Environment Effect

Route of Administration Temperament Clinical signs Status of debilitation ANIMAL FACTORS

Injectable Routes of Administration Injectable routes are parenteral Most common injectable administration routes are intravenous IV, intramuscular IM, and subcutaneous SQ/SC Drugs given by injectable administration routes may be aqueous solutions or emulsions (mixtures of two immiscible liquids)

IV 25 degrees

Alexander Wood ( ) Dr Wood first injected a patient with morphine in His wife became the first IV morphine addict. The first recorded fatality from a hypodermic-syringe induced overdose was Dr Wood's wife.

Designed by Francis Rynd ( ), this instrument was used for deep injections. It is made of steel with an ivory handle, and was manufactured by Weiss. Rynd, an Irish physician, invented the hollow needle in 1844.

Vehicle of Administration End of the barrel where the needle is attached Slip–lok or Luer-lok TIP Holds medication Calibrations BARREL End of a barrel Support FLANGE Tight fitting seal Aspirate and dispense medication PLUNGER

Figure 3-5 to 3-7 Various size disposable syringes Safety syringes Various lengths and sizes of needles Parts of a needle

Trypanophobia TRYPANOPHOBIA is the extreme and irrational fear of medical procedures involving injections or hypodermic needlesirrational fearmedical proceduresinjections hypodermic needles

Prefixes Intra – within Inter – between Sub – under Epi – above Trans - across

Intravenous (IV) – Rapid onset of action – Predictable concentration of drug levels in body – Immediate response – Initially higher levels than other routes initially – Shorter duration of action – Facilitates administration of an irritating drug – Most are aqueous solutions, few emulsions

Intravenous (IV) BOLUS: injecting a concentrated mass of a drug in a minute amount of fluid with only a needle and syringe. Used to achieve immediate high concentrations of drugs. INTERMITTENT: diluting a drug dose in a small volume of fluid and administering it during a minute period via an indwelling catheter. Used to maintain blood levels of antibiotics. INFUSION: administration of large volumes of fluid continuously over extended periods of time

Intravenous (IV) RISKS Drug could be administered too rapidly Injection not performed in a sterile manner Drugs not properly mixed Risk of air or foreign particles causing an embolus Perivascular necrosis and inflammation

Intramuscular Onset of action within ~30 minutes Provides reliable blood levels Longer duration of action than IV, shorter duration of action than oral No irritating solutions Option for fractious animals Absorption depends on vehicle, rate depends on formulation

Intramuscular Rate of absorption depends on formulation (solution vs. suspension) and vehicle Aqueous solution – clear liquid preparation that contains one or more solvents and one or more solutes. Blood levels within 5 minutes. Aqueous suspension, oily suspension and injectable – liquid preparation that contains solid drug particles suspended in a suitable medium. Absorbed more slowly – prolonged introduction into the bloodstream. Repository / Depot preparation – Placing an injectable drug in a substance (such as an oil) that delays absorption (ex: Depo-Medrol). Depo = long acting

Intramuscular RISKS – Always pull back on the plunger to be sure that you are not in a blood vessel before you inject – Don’t give the injection too shallow; you risk not getting the drugs into the muscle – IM injections can be painful

Subcutaneous Placing a drug into the connective tissue underneath the dermis of the skin Faster onset than oral, slower than IM (fewer blood vessels) Longer duration of action than IM No irritating solutions Can inject large volumes (SC fluids) Blood levels are similar to oral administration Temperature affects absorption

Onset of actionDuration of activity SuspensionBenefitsRisks IV Rapid Short Re dosed more often Mostly aqueous Few emulsions Give large volumes Immediate response Sterile Give slowly Properly mixed Bubbles - emboli IM Relatively rapid (5-30 mins) Longer than IV Shorter than oral Aqueous solutions Aqueous/ oily suspension Injectable pellets Can dose less frequently Fractious animals No irritating substances SQ Slower than IM Faster than oral Longer than IM Water soluble solution For large vol. non irritating water soluble solution Injectable pellet Increase absorption by temp No irritating substances

Intramammary Injections Typically have fast and even distribution and a low degree of binding to udder tissue Results in lower concentrations of drug residues in the milk Particle size important: small in non-lactating cattle

Other Injectable Routes Intraperitoneal –R–Risk of peritonitis and penetrating organs –L–Large surface area for blood absorption Epidural/Subdural/Intrathecal –D–Diagnostic procedures and administering anesthetic agents –R–Risks of spinal injections or drugs traveling cranially

Other Injectable Routes Intra-arterial –U–Used to treat a specific organ (very high levels at a certain site) –C–Can be done accidentally Intradermal –B–Between dermis and epidermis –L–Low blood levels, slow absorption –L–Local treatments or allergy testing

Other Injectable Routes Intracardiac – Rapid blood levels – Emergencies and euthanasias Intra-articular – Must use aseptic technique Intramedullary/Intraosseous – Rapid blood levels – Not common, painful – Rapid fluid administration (femur/humerus)