Principles and Methods of Drug Administration CHAPTER 3 L. VanValkenburg, RVT, BAS

Safe Drug Use All drugs are potential poisons. Veterinarian and RVT are accountable for safe drug administration Know components of drug order and question anything that is not complete, is unclear, or does not make sense. Verbal drug orders should be documented ASAP. When preparing and administering meds: Gather supplies first!  Clean hands, clean supplies, etc. Well-lit work area with minimal distractions

The Six “Rights” of Proper Drug Administration Right Drug Right Dose Right Time Right Route & Technique Right Patient Right Documentation

The Right Drug “The right drug” means the patient received the drug that was prescribed. When filling a prescription or preparing to administer a drug, read label on the container 3 times! Never give a medication from a container that is unlabeled It is important to understand why the patient is receiving the drug Convenia vs. Cerenia Prednisone vs. Prednisolone

The Right Dose The right dose is the dose prescribed for a particular patient DVMs and RVTs must calculate each drug dose accurately. Before calculating a drug dose, an estimate of the answer based on prior knowledge should be predicted. When in doubt, have the dose recalculated by another DVM or RVT.

The Right Time The right time is the time at which the prescribed dose should be administered Daily drug doses are given at specific times during the day to keep plasma levels within desirable concentrations. Do you know what SID, BID, TID, and QID mean? What about q24H, q12H, q8H, and q6H? PRN?

The Right Route and Technique The right route is the proper route of administration, so that the patient takes the whole dose at one time Drugs should also be administered at the appropriate site in order to obtain the desired effect. Some routes of administration are not feasible for some animals.

The Right Patient The right patient means the RVT or DVM makes certain that the medication is given to the proper patient If patient is in a cage check the cage card and ID band. If the patient is in the exam room, identify the patient by name. When dispensing medication, read the patient’s name to the owner to ensure the right animal gets the right medication.

The Right Documentation The right documentation requires the person administering the drugs must immediately record the appropriate information about the drug given Name of drug Dosage administered Time and date administered The route and site of administration Patient response DVM signature or initials

The Right Documentation The right documentation is a legal and safety obligation “If it was not documented, it was not done.” Legally, controlled substances must also be recorded in a drug log. It should also be documented if an owner refuses drug treatment for his/her animal including the reason for refusal

Informed Consent Without the client’s consent, the medication cannot be given! Clients refuse because of: Lack of knowledge Misconceptions Past problems with drug Inability to ‘cure’ patient Inability to medicate pet themselves Financial limitations

Our Therapeutic Goal is to: Achieve drug concentrations at the site of action (target tissue)… that are sufficiently high enough to produce the intended effect… without producing adverse drug reactions. Just right Too little Too much

Drug Concentrations in the Plasma 50 40 30 20 10 But what’s missing here that is needed for this info to be of any use? Drug Concentration in Plasma (Cp) mcg/mL 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Time since administration of drug (hours)

Drug Concentrations in the Plasma Toxic Concentrations 50 40 30 20 10 Drug Concentration in Plasma (Cp) mcg/mL Therapeutic Concentrations (Therapeutic Range) Subtherapeutic Concentrations 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time since administration of drug (hours)

Route of administration Therapeutic Range The therapeutic range of a drug is the drug concentration in the body that produces the desired effect in the animal with minimal or no signs of toxicity. Three major drug factors keep drugs in their therapeutic range: Route of administration Drug dose Dosage interval

Therapeutic Range Other factors that play a role in getting and keeping drugs within the therapeutic range include: Drug properties Health and physiology of the animal Maintaining drugs within range involves maintaining a balance among: Rate of drug entry into body Absorption of drug Distribution of drug Metabolism of drug Excretion of drug YOU WILL LEARN MORE ABOUT THESE THINGS IN THE NEXT CHAPTER 

Routes of Administration Oral (PO) (Non-parenteral) Parenteral routes: Sublingual Intradermal (ID) Via feeding tube Subcutaneous (SC or SQ) Intramuscular (IM) Topical Intravascular/intravenous (IV) Transdermal Intraosseous/Intramedullary Intranasal Intraperitoneal (IP) Inhalation Intra-arterial (IA)*** Nebulized or volatilized Intra-articular Rectal (PR) Epidural/subdural/intrathecal Aural Intracardiac (IC) Topical ophthalmic Intramammary

Routes of Administration Parenteral drugs are given by a route other than the GI tract Nonparenteral drugs are given through the GI tract (orally) Factors that affect the route of drug administration include: Drug factors Patient factors

Drug Factors Some drugs cause one effect when given parenterally and another effect when given non-parenterally. magnesium sulfate causes muscle relaxation when given IV and diarrhea when given orally Some drugs are insoluble in water and can be given IM but cannot be injected IV – Always be aware of label! Some drugs are destroyed by stomach acid and cannot be given orally. Some injectable drugs must be given very slowly; while others must be given in a bolus. Cost and availability of drug must also be considered.

Patient Factors Animals that are actively vomiting cannot absorb drugs given orally. Critically ill patients need to get therapeutic levels of drug into their bodies rapidly. The animal’s temperament must be considered. Can/will the owner medicate their animal at home properly with the medication as prescribed?

Other Factors to Consider Is restraint going to be an issue? Are systemic effects expected or is just a local effect preferred? What is your time frame? Does this medication require that special precautions be followed during administration (i.e. gloves, mask)? Potential side effects? What is the most convenient route of administration for the owner?

Parenteral Administration

Designed by Francis Rynd (1801-1861), 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. Dr Wood first injected a patient with morphine in 1853. His wife became the first IV morphine addict. The first recorded fatality from a hypodermic-syringe induced overdose was Dr Wood's wife. History: Lagniappe

Anatomy of a Syringe Bevel Needle Cap Needle hub Luer-lock tip Barrel Rubber stopper Scale Plunger Flange Thumb rest

Comparison of Common Parenteral Routes of Drug Administration Intramuscular 90° Subcutaneous 45° Intravenous 25° Intradermal 10°–15° Epidermis Dermis Subcutaneous tissue Muscle

Parenteral Drug Forms Sterilized solutions Prepackaged syringes with needles Powders that must be reconstituted with a sterile diluent Vials (single or multi-dose) Ampules

Intravenous (IV) RAPID onset of action, HIGHER initial body levels of drug, and SHORTER duration of activity Drug concentration is predictable. Injection techniques include: BOLUS administration, INTERMITTENT therapy, and INFUSION of fluid In most cases, IV drugs should be given slowly Remove air bubbles! Usually water soluble drugs; rarely emulsions Avoid perivascular injection of IV drugs.

Intramuscular (IM) RELATIVELY RAPID onset of action and LONGER duration of activity than IV drugs Blood levels reliable and typically significant in ~30 minutes. Absorption rate depends on drug formulation Repository or depot preparations delay absorption Ex: Procaine penicillin G and Depo-Medrol (methylprednisolone) IM drugs can be in aqueous solutions or suspensions. Solutions are clear liquids that contain one or more solvents and one or more solutes. Suspensions are liquid preparations that contain solid drug particles suspended in a suitable medium.

Subcutaneous (SC) SLOWER onset of action and LONGER duration of activity than IV and IM drugs; FASTER onset than PO admin. Blood levels LESS RELIABLE than IV or IM Absorption rate affected by the vehicle in the preparation and temperature. Larger amounts of solutions can be given SQ Cannot use irritating solutions! Pellets can also be implanted into the subcutaneous space

Intramammary 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 In what instance do you think would we use this route of administration?

Other parenteral administration routes are listed in Table 3-1 in your textbook. READ IT…IT IS TESTABLE MATERIAL!!!

Local Routes of Administration Inhalation administration introduces drug to the animal by having it breathe the drug into the lungs RAPID ABSORPTION; particles diffuse across the alveolar membrane and enter blood capillaries. Must be AEROSOLIZED, VOLATILIZED, or NEBULIZED

Topical medication goes on the surface of skin or mucous membrane GELS TINCTURES OINTMENTS LOTIONS CREAMS POWDERS PASTES AEROSOLS LINIMENTS Topical medication goes on the surface of skin or mucous membrane SLOWEST systemic absorption rate Used for LOCALIZED treatment Fur and feathers inhibit good skin contact. Includes OPHTHALMIC and OTIC medications.

Rectal ALTERNATIVE for delivering drugs to animals that present dangers to the vet staff or animals in very poor condition where other methods of admin. are not practical. Anticonvulsants, analgesics, antiemetics Local irritation is a potential side effect of rectal drug therapy. Suppositories are designed for PR admin., however, other drug forms can be successfully admin. PR.

Transdermal Delivered SYSTEMICALLY through a patch on the skin Through the patch, drug passes from skin to bloodstream allowing it to be delivered slowly and continuously (hours, days, or longer) Plasma levels = relatively CONSTANT Skin irritation is one side effect Useful for drugs that are normally eliminated rapidly from the body Only drugs needed in relatively small daily doses can be given through patches Typically mixed with chemical to enhance skin penetration Ex: Fentanyl and Niroglycerin

Enteral Administration: Oral Route (PO) Delivers drug directly to the GI tract Most CONVENIENT route of admin.; LEAST LIKELY to cause adverse reactions SLOWER onset of action; LONGER duration of activity Absorption is not always predictable. Affected by GI disease, A&P of digestive tract Before entering the bloodstream, an oral drug must be: released from the dose form transported across the GI tract passed through the liver

Solid Dose Forms TABLETS CAPLETS CAPSULES LOZENGES BOLUSES POWDERS Enteric-coated Sustained-release (SR) Scored MOLDED TABLETS CAPLETS CAPSULES LOZENGES BOLUSES Via “balling gun” POWDERS

Liquid Dose Forms Given via dropper, syringe, or drench or mixed with food. SOLUTIONS Syrups (85% sucrose) Elixirs (sweetened alcohol) Tinctures (alcohol) SUSPENSIONS EMULSIONS Can you think of any contraindications here? Advantages/disadvantages of giving with food?

Absorption of Oral Drug Forms Transport across the GI tract determines how long it takes for a drug to enter the bloodstream. LONGER length of time in ruminants and herbivores (horses, rabbits, etc.) The more COMPLEX the digestive tract, the LONGER it takes to attain therapeutic blood levels. Drug passage through liver affects drug concentration in the blood. “First-Pass Effect” Liver alters drug and makes it less (or more) active

Drug Dose The dose of a drug is the amount of drug administered at one time to achieve the desired effect (can be in mL, cc, mg, g, tablets, etc.) Loading dose: initial dose of drug given to get the drug concentration up to the therapeutic range in a very short period of time Maintenance dose: dose of drug that maintains or keeps the drug in the therapeutic range Total daily dose: total amount of drug delivered in 24 hours

Drug Dosage The dosage of a drug is the amount of drug per animal species’ body weight or measure Examples include mg/kg or g/lb Dosage interval: how frequently the dosage is given Examples include BID or TID Dosage regimen: dosage interval and the dosage together Examples include 30 mg/kg TID and 5 g/lb BID

Drug Toxicity Drug toxicity may be due to human error or be related to side effects of the drug Examples of drug toxicities: Outright overdose Relative overdose Side effects Accidental exposure Interaction with other drugs Incorrect treatment

Counteracting Drug Toxicity Veterinary staff must act quickly to counteract any problems caused by drug treatment. Some ways to treat drug toxicities: Removal of the offending drug Enhancing drug removal by the animal (inducing emesis, administering fluids, etc.) Counteracting with an antidote Providing symptomatic care or nursing care until the toxicity signs have diminished