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Pharmokinetics/ Pharmacodynamics

Pharmokinetics/ Pharmacodynamics. CHAPTER 4 - 1 Dr. Dipa Brahmbhatt VMD MpH dbrahmbh@yahoo.com. Objectives. Factors that affect movement of drug molecules throughout the body Route of drug administration Physiologic factors that change the way drugs move in the body. PHARMACOLOGY TERMS.

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Pharmokinetics/ Pharmacodynamics

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  1. Pharmokinetics/ Pharmacodynamics CHAPTER 4 - 1 Dr. DipaBrahmbhatt VMD MpH dbrahmbh@yahoo.com

  2. Objectives • Factors that affect movement of drug molecules throughout the body • Route of drug administration • Physiologic factors that change the way drugs move in the body

  3. PHARMACOLOGY TERMS

  4. Therapeutic Range/ Therapeutic window • Ideal range of drug concentration within the body • Maximum effective concentration • Border btw beneficial and toxic conc. • Toxic conc. • Minimum effective concentration • below this concentration there is no benefit • Subtherapeutic conc.

  5. 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

  6. Therapeutic Range/ Therapeutic window • Perfect balance • Drug in = drug out • Drug dose, elimination/ metabolism of drug and therapeutic range • Liver and Kidney failure • Reduce dose as metabolism/ elimination compromised • PU/PD • Increase dose as rate of elimination increased .

  7. Dosage Regimen • Therapeutic administration: Balance between dose, dosage interval and route of administration • Dose: drug at one time: mg, g, grains, mg/ml • Loading dose: Higher, once esp. emergency: shock dose fluids, tapering dose steroids, Albon • Maintenance dose: smaller amount more frequent

  8. Dosage Regimen • Dosage interval: s.i.d; b.i.d, t..i.d (Table 3-1) • Error: q.i.d and qd (4 times more) • Total daily dose: 100 mg T given 4 times/day = 400mg • Adjust dosage interval based on client compliance • Reduce drug interval: wider swing of conc. • Can lead to above max. effective conc. And under the minimum effective concentration = subtherapeutic conc.

  9. Trypanophobia • TRYPANOPHOBIA is the extreme and irrational fear of medical procedures involving injections or hypodermic needles

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

  11. Routes of Administration Non-Parenteral • Oral (per os) • Sublingual • Via feeding tube • Topical: lotion/liniment • Transdermal • Intranasal • Inhalation • Nebulized or volatilized • Rectal (PR) • Aural • Topical ophthalmic • Parenteral: beside/beyond/apart from GI • Intradermal (ID) • Subcutaneous (SC or SQ) • Intramuscular (IM) • Intravascular/intravenous (IV) • Intraosseous/Intramedullary • Intraperitoneal (IP) • Lab animals when IV/IM not accessible • Administer large vol. of fluids • Intra-arterial (IA)*** • Intra-articular • Epidural/subdural/intrathecal • Intracardiac (IC) • Intramammary

  12. Parenteral Administration

  13. Intravenous (IV): towards the heart • 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 • Oxytet. • IV bolus: large vol. at one time > pour • IV infusion steady state/ plateau > dribble • Extra vascular or perivascular injection: propofol! • Most are aqueous solutions, few emulsions (filter needle/ hub) • No air bubbles

  14. Routes of Administration • Intra – arterial: high conc. directly to tissues and can led to local toxicosis

  15. References • Romich, J.A. Pharmacology for Veterinary Technicians, 2nd edition. 2010. • Bill, R.L. Clinical Pharmacology and Therapeutics for the Veterinary Technician, 3rd edition. 2006.

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