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Vakul Aren
Vakul Aren, Doctor
Category: Medical
Satisfied Customers: 3518
Experience:  MBBS,DTM&H,34 years of experience
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briefly discuss the influence of absorption,distribution,metabolism

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briefly discuss the influence of absorption,distribution,metabolism and excretion of drugs in general of the older client
The elderly or the geriatric population constitutes about 13% of the population but consumes about 1/3 rd of all drugs prescribed in the US.The problems are compounded by the fact that multiple problems need to be treated including chronic diseases and acute complaints.Many changes occur in the elderly which may affect absorption of the drug.These include a increase in gastric emptying time,reduced saliva production,reduction in gastric acid production,reduced drug absorptive capacity by the cells of intestinal mucosa,decreased splanchnic blood flow and finally slowing of the gastric motility.This affects the timing and interference with food of the drug in the elderly.The distribution is affected by a decrease in the body weight ,decrease in total body water,decrease in serum albumin levels,increase in alpha-1 glycoprotein,increase in total body fat and altered protein binding capacity for the protein bound drugs.This will affect the water soluble drugs and there may be a narrower therapeutic window which may exhibit toxic effects at lower levels for some drugs.Fat soluble drugs and protein bound drugs are also affected by age hence their doses may need adjustment.Lower binding capacity of the albumin may lead to higher free molecules of protein bound drugs.The metabolism of the drug is affected by the reduced liver mass and decreased blood flow to the liver. There is a decrease in the first pass metabolism,hence more free drugs are available of the bioavailable drugs,there may be need to lower the doses for the elderly patient with such drugs like antiarrhythmic drugs and phenytoin.Polypharmacy,ingestion of alcohol and smoking may also affect the drug metabolism and pharmacokinetics.rug execretion is mainly through the kidneys,this may be affected due to reduced kidney mass,reduced tubular absorption/clearance and reduced renal blood flow.Reduction in glomerular filteration and creatinine clearance will also affect drug clearance from the body.
I will be happy to address any specific query you may have.
The doses used in the elderly tend to be lower,since the number of drugs required for the various ailments is on the higher side, drug interactions need to be kept in mind.Similarly albumin bound drugs and water soluble drugs need to be evaluated and started at a lower dose .Decreased renal clearance will also be a factor,as the line between therapeutic levels and serum levels when side effects are seen tend to be blurred.
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