Fundamentals of Pharmacology for Veterinary Technicians

1. Fundamentals of Pharmacology for Veterinary Technicians Chapter 3 Therapeutic Range and Routes of Administration © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

2. The Therapeutic Range • All drugs should be considered potential poisons and should be dispensed and given with great care • 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 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

3. Keeping Drugs in the Therapeutic Range • Three major drug factors keep drugs in their therapeutic range: • Route of administration • Drug dose • Dosage interval © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

4. Route of Administration • Parenteral drugs are given by a route other than the gastrointestinal tract • Nonparenteral drugs are given through the gastrointestinal tract • Factors that affect the route of drug administration include: • Drug causes one effect when given parenterally and another nonparenterally • Water-insoluble drugs can be given IM,but not IV • Some drugs are destroyed by stomach acid and cannot be given orally © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

5. Injectable Routes of Administration • Injectable routes are parenteral • Most common injectable administration routes are IV, IM, and SQ • Drugs given by injectable administration routes may be aqueous solutions or emulsions (mixtures of two immiscible liquids) © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

6. Injectable Routes of Administration (IV) • Drugs given IV have rapid onset of action, higher initial body levels of drug, and shorter duration of activity • IV injection techniques include bolus administration, intermittent therapy, and infusion of fluid • In most cases, IV drugs should be given slowly • All air bubbles must be removed from the drug before administration to avoid causing air emboli and tissue damage © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

7. Injectable Routes of Administration (IM) • Drugs given IM have relatively rapid onset of action and longer duration of activity than IV drugs • Absorption rate depends on drug formulation • IM-injectable drugs may be in a substance that delays absorption; these are referred to as repository or depot preparations • 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 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

8. Injectable Routes of Administration (SQ) • Drugs given SQ have slower onset of action and longer duration of activity than IV and IM drugs • Absorption rate may be altered by the vehicle in the preparation • Larger amounts of solutions can be given SQ; amount given should be based on animal species involved • Pellets can also be implanted into the subcutaneous space • The rate of absorption of SQ fluid can be manipulated by temperature • Applying heat to the area increases the rate of absorption • Applying cold to the area decreases the rate of absorption © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

9. Other Parenteral Administration Routes • Inhalation administration introduces drug to the animal by having it breathe the drug into the lungs • Particles diffuse across the alveolar membrane • Topical medication goes on the surface of skin or mucous membrane • Forms of topical medication are summarized in Table 3-2 • Other parenteral administration routes are listed in Table 3-1 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

10. Nonparenteral Administration Routes • Oral administration delivers the drug directly to the animal’s gastrointestinal tract • Before entering the bloodstream, an oral drug must be released from the dose form, transported across the GI tract, and passed through the liver • Oral drugs usually have slower onset of action, longer duration of activity, and absorption rates that may be affected by the type of digestive tract and/or GI disease • Oral drugs may be tablets, capsules, boluses, powders, solutions, suspensions, or emulsions © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

11. 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 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

12. 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 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

13. Drug Toxicity • Drug toxicity may be due to human error and/or accident • Drug toxicity may 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 © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.

14. Counteracting Drug Toxicities • 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 • Counteracting with an antidote • Providing symptomatic care or nursing care until the toxicity signs have diminished © 2004 by Thomson Delmar Learning, a part of the Thomson Corporation.