Elderly Patients

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DRUG DOSAGE IN ELDERLY PATIENTS By Asif Mahmood :

DRUG DOSAGE IN ELDERLY PATIENTS By Asif Mahmood

Contents:

Contents Elderly/Geriatrics patients Classification of elderly 3. Factors to be considered in Geriatric drug therapy. 4. Physiologic Factors

Contents………:

Contents……… 5. Pharmacodynamic Factors 6. Pharmacokinetic Factors i.e. LADMER System 7. Dosage Regimen 8. Equations/Formulas

Elderly/Geriatrics patients :

Elderly/Geriatrics patients Definition Defining "elderly'' is difficult. The geriatric population is often arbitrarily defined as; “Patients who are older than 65 years” “Older Elderly'' is defined as; “People who are living more than 85 years”

Geriatric Patients :

Geriatric Patients The term "elderly" is subject to varying definitions with regard to chronologic age. The functional capacities of most organ systems decline throughout adulthood and important changes in drug response occur with advancing age .

Geriatric Patients……..:

Geriatric Patients…….. Geriatric medicine or geriatrics is the field that encompasses the management of illness disability in the elderly.

Geriatric patients……:

Geriatric patients…… Many elderly patients have coexisting pathologies that require multiple-drug therapies . Medications in the elderly are prescribed not only to relieve symptoms and manage diseases but also to improve bodily function, enhance the quality of life , and prolong survival.

Classification of Elderly:

Classification of Elderly Chronologically, the elderly have been arbitrarily classified as Y oung old (ages 65–75 years) O ld (ages 75–85 years) O ld old (age > 85 years)

Factors to be considered in Geriatric drug therapy:

Factors to be considered in Geriatric drug therapy Physiological Factors Pharmacodynamic Factors Pharmacokinetic Factors

1- PHYSIOLOGIC FACTORS:

1- PHYSIOLOGIC FACTORS Overall decrease in vital physiological functions from 10% to 30% in elderly subjects as compared to young adults.

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Continue….. Decline in neurological functions Decline in Renal function Decline in GI Function Decrease in Cardiovascular functions Decline in Pulmonary functions Alteration in stratum corneum Decrease in hepatic reserves Decrease in serum albumin Concentrations

2- PHARMACODYNAMIC FACTORS:

2- PHARMACODYNAMIC FACTORS The quantity of receptors The quality of receptors Homeostasis

Quantitative Alterations:

Quantitative Alterations No. of drug receptors are decreased. For example: Muscarinic, Parathyroid Hormone, β - Adrenergic, α 1 - Adrenergic and µ - Opioid Receptors are decreased with increasing age.

Qualitative Alterations:

Qualitative Alterations Alteration in receptor sensitivity Benzodiazepines, Opioid Analgesic, Warfarin and heparin have increased response in elderly as compared to Adults. While in contrast certain drugs such as β – agonist/antagonist have decreased response.

Homeostasis:

Homeostasis “The existence of the stable internal Enviroment of the body”. Inefficient homeostatic adjustments in elderly e.g. Impaired baroreceptor function result in orthostatic hypotension. orthostatic hypotension is aggravated with drugs such as TCA’s and diuretics

3- PHARMACOKINETIC FACTORS:

3- PHARMACOKINETIC F ACTORS LADMER System It deals with the complex dynamic process of liberation of an active ingredient from dosage form, its absorption into systemic circulation, its distribution and metabolism in the body, the excretion of the drug from the body and the achievement of response.

LADMER System…….:

LADMER System……. L iberation A bsorption D istribution M etabolism E xcretion R esponse

Liberation :

Liberation It is the release of an active ingredient from the dosage form in vivo. Onset of action R ate of absorption Availability

Factors affecting drug liberation in aged Pt’s:

Factors affecting drug liberation in aged Pt’s Route of Drug administration Factors altered Possible Consequences PO Gastric Secretion Gastric PH Gastric Motility Delayed Dissolution Change in Deg. Of Ionization Delayed Dissolution IM Tissue perfusion rate Delayed Dissolution of solid particles Topical Skin Hydration Delayed release

Age-Dependent Alterations in Drug Absorption:

Age-Dependent Alterations in Drug Absorption Rate of drug absorption Extent of drug absorption First Pass effect e.g. Morphine and Propranolol

Age-Dependent Alterations in Drug Distribution:

Age-Dependent Alterations in Drug Distribution Systemic flow rate, cardiac output and TBF TBF in males = 0.37% Females = 0.27% Drug PPB may decrease as a result of decrease in the albumin concentration The apparent Vd is changed due to a decrease in muscle mass and an increase in body fat. High Drug Conc.

PowerPoint Presentation:

Age-Dependent Alterations in Drug Metabolism Decrease in liver size with increasing age Decrease in hepatic blood flow The activity of the enzymes responsible for drug biotransformation may decrease with age, leading to a decline in hepatic drug clearance . Examples: Morphine, Propranolol and Verapamil

Age-Dependent Alterations in Drug Excretion:

Age-Dependent Alterations in Drug Excretion Half Life of Renaly excreted drugs is increased. GFR and Renal Blood Flow. Renal excretion is decreased with the increasing age.

Continue….:

Continue…. Active tubular secretion GFR decreases at a mean rate of 1% per year after 40 years of age . EXAMPLE: Digoxin and Aminoglycosides

Age-Dependent Alterations in Drug Excretion…..:

Age-Dependent Alterations in Drug Excretion….. Decreased Vd Decreased Rate of Elimination Higher Drug Accumulation Higher Steady state Blood Levels Incidence of Higher Side Effects & Toxicity in Aged Patients

Cockroft- Gault Equation:

Cockroft- Gault Equation Males: Crcl (ml/min) = [(140-age) x IBW] / ser.cr x 72 if TBW< IBW than use TBW for Crcl measurement If TBW>IBW than use IBW for Crcl measurement

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Continue…. IBW for males IBW = 50kg + 2.3kg for each inch over 5 ft. IBW for females IBW= 45.5kg + 2.3kg for each inch over 5 ft.

Dosage Regimen:

Dosage Regimen “It is a systematized dosage schedule for therapy” i.e. Proper dose size at proper dose interval for clinical effectiveness. It should be I ndividualized for elderly

PowerPoint Presentation:

Individualization of Drug Dosage Regimens The application of pharmacokinetic principles to dosage regimen design while considering Individual variation in pharmacokinetics and pharmacodynamics profile. Narrow therapeutic index drugs Example: Digoxin, Phenytoin and carboplatin

Reasons for Drug Dosage Adjustment in Elderly :

Reasons for Drug Dosage Adjustment in Elderly Vital Physiologic Functions Tend to Change with Aging Pharmacodynamic Hypothesis Age-Dependent Alterations in Drug Absorption

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Continue…… Age-Dependent Alterations in Drug Distribution Age-Dependent Alterations in Drug Metabolism Age-Dependent Alterations in Drug Excretion

Considerations for Drug Dosage in Elderly:

Considerations for Drug Dosage in Elderly Dose adjustment may be based on the therapeutic response . The patient's physical condition may determine the drug dose and the route of administration employed . The dose may be determined, in part, on the patient's weight , body surface area, health and disease status and pharmacokinetic factors.

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Continue….. Concomitant drug therapy may affect drug/dose effectiveness. A drug's dose may produce undesired adverse effects and may affect patient compliance . Complex dosage regimens of multiple drug therapy may affect patient compliance.

Dose Calculation:

Dose Calculation Pt’s Dose = (Weight in Kg) 0.7 (140-age) x Adult dose 1660

Loading Dose:

Loading Dose LD = Vd (L/Kg) x IBW (Kg) x Desired Cp (mg/L)

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