A Drug Therapy Smorgasbord Practical Issues for Dietitians. Presented by David B. Goldwater R.Ph Clinical Consultant Pharmacist. Objectives. Review Practical Pharmacokinetic principals to create a deeper understanding of absorption, distribution and excretion of drugs.
David B. Goldwater R.Ph
Clinical Consultant Pharmacist
Basic Concepts of Pharmacokinetics
Concentration in plasma
RATE of elimination
Clearance x Concentration in the blood.
Elimination HALF LIFE (t1/2)
Time taken for plasma conc. to reduce by 50%.
100% Elimination After 5 HALF-LIVES
(Symbol for Half-life is t ½)
E.g. DIGOXIN ……t ½ = 40hrs
Q. Why does a patient wake up after 5 minutes after an injection of Thiopentone, when we know that it takes several hours to eliminate this drug from the body?
A. Initially the drug is ALL in the blood and this blood goes to "vessel rich" organs; principally the brain.
Rapid distribution phaseα
Equilibrium phase (Plateau)
(for a drug given orally)
BIOAVAILABILITY is the AREA UNDER THE CURVE
The strategy for ADMINISTRATION DOSING is to administer ONLY, sufficient amounts of drug to attain therapeutic effect, but not enough to produces toxicity!
THEREFORE WE APPLY THESE PRINCIPLES……
This is why we give a higher dose of ORAL morphine, for the equipotent INTRAVENOUS dose
30 MGORAL Morphine is EQIPOTENT TO
1 MGIV Morphine.
ORAL: PARENTERAL RATIO =3 : 1
FACTORS THAT EFFECT WHERE THE DRUG ENDS UP:
Why is this important?
RESULTS in a 50% increase in FREE DRUG-A concentration from 3% to 6%
RESULTS in a NEGLIGIBLE increase of FREE DRUG-X concentration from 30% to 33%
The HIGHLY BOUND drugs that we really need to focus on are: warfarin, diazepam, propranolol,phenytoin.
Warfarin Resistance & Enteral feeding: New understanding of An Old Problem
NOT LIKELY !
in healthy adult men :
In healthy adult women:
TheGRAND TOTALofdietary vitamin K intake was 205 mcg /day
for patients receiving INTERMITTENT tube feedings.
Other Drug-Enteral feeding interactions
Roland N. Dickerson, George O. Maish III, Gayle Minard and Rex O. Brown.
Clinical Relevancy of the Levothyroxine − Continuous Enteral Nutrition Interaction
Nutr Clin Pract 2010 25: 646
patients receiving concurrent levothyroxine and
EN therapy is recommended.
NON-FDA-APPROVED INDICATION †
† For the treatment of anorexia, cachexia, or unexplained weight loss in the elderly.
IS EQUIVALENT UNDER FED CONDITIONS
EFFECTIVE SERUM LEVELin UNFED Condition
The fed condition is achieved by subjects eating a high-calorie & high-fat meal.
HIGH-CALORIE (800-1000 calories)
*** Plus ***
HIGH-FAT (aprox 50% of total calories)
Could a resident who is not eating actually ingest 100% of this mealprior to admin of Regular Megacesuspension?
* D. Rudolph : Appetite Stimulants in Long Term Care: A Literature Review. The Internet Journal of Advanced Nursing Practice. 2010 Volume 11 Number 1
Newest ORAL Anticoagulant Since The Approval of Warfarin (Over 50 Years Ago)
D a – bee – g´a t t – t r a n
Approved October 2010
USA INDICATIONS AT THIS TIME !
ADDITIONAL INDICATION (Approved in Canada and Europe (Only!)
Warfarin has a long history of SUCCESSFUL clinical use but also has many limitations to its use.
Particularly Dangerous Drug (Over 50 Years Ago)Interactions In Long Term CareCompiled by AMDA American Medical Directors Association & ASCP American Society of Consultant Pharmacists
Cmax = Maximum Concentration
DABIGATRAN is NOT APPROPRIATE in the following situations:
Metabolic Effects of Atypical Antipsychotics
+ LOW+++ MODERATE-HIGH++++HIGH
[+]increased effect[D]discrepant results[─]no effect[ ** ]Newer Drugs w/ limited long term data
American Diabetes Assoc; American Psychiatric Assoc; American Assoc of Clinical Endocrinologists; North American Assoc for the Study of Obesity. Diabetes Care.2004; 27:596
Body Mass Index17,26
= BMI (kg/m2)
Overweight BMI =25-29
Obesity BMI> 30
Abdominal obesity waist circumference17
MEN > 102 cm (40 in)
Women >88 cm (35 in)
Selected References (Over 50 Years Ago)
6. Lahaman AF et al: Working Group on Schizophrenia. American Psychiatric Association. Practice Guidelines for the treatment of patients with schizophrenia, 2nd edition. Am J Psychiatry 2004;161 (suppl-2):1-56
30. Lelter LA et.al. Diabetes Screening in Canada. DAIASCAN Study:Prevelence of undiagnosed diabetes and glucose intolerance in family physician offices. DIABETES CARE 2001 24(6) 1038-43
American Diabetes Association: American Psychiatric Association: American society of Clinical Endocrinologists: North American Association for the Study of Obesity. Diabetes Care 2004: 27: 596. Gangul R. J Clin Psychiatry: 1999; 60 (Suppl 21): 20-24.
The CATIE TRIAL (Clinical Antipsychotic Trials of Intervention Effectiveness) N Eng J Med 2005;353:1209-1223 * Data for Clozapine & Aripiprazole are from separate sources