Post on 23-Jun-2015
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Patient Related Factors
Affecting drug absorption
Presented by,Presented by,Hinglajia Hetal RatilalHinglajia Hetal Ratilal
Patient Related Factors
Age
Age
Infants• Gastric pH high
• Intestinal surface low
• Blood flow to GIT low
Elderly persons Altered gastric emptying
Decreased intestinal surface area & GI blood flow
Higher incidents of achlorhydria
Bacterial overgrowth
Altered Absorption pattern
Gastric Gastric emptyingemptying
Gastric emptying
Apart from dissolution of a drug & its permeation through
the bio membrane, the passage from stomach to the small
intestine, called as gastric emptying.
Rate limiting step, because the major site of drug absorption
is intestine.
It increases bioavailability of a drug.
It is first order process.
Rapid gastric emptying Rapid gastric emptying advisable where,advisable where,
Delay gastric emptying advisable where,
Gastric acid quantifying parameters
• Gastric emptying rate is the speed at which the
stomach contents empty into the intestine.
• Gastric emptying time is the time required for the gastric content to empty into the small intestine.• Longer the gastric emptying time , lesser the gastric
emptying rate.
• Gastric emptying t1/2 is the time taken for half the stomach contents to empty.
Factors affecting on gastric emptying
Intestinal transitIntestinal transit
Intestinal transitIntestinal transitSmall intestine- major site for drug absorption, long
intestinal transit is desirable for complete drug
absorption
The residence time depends on the intestine that
occurs due to peristaltic contractions..
It promotes drug absorption by,
Increasing drug intestinal membrane contact,
Enhancing dissolution especially poorly soluble drugs,
through induced agitation.
Delayed intestinal transit is desirable for,
Intestinal transitIntestinal transit
Promotes..
Diarrhea
Laxatives
Drugs like metoclopramide
Demotes..
Food
Pregnancy
Anticholinergics
Gastrointestinal pHGastrointestinal pH
107 fold difference in the H+ ion concentration is observed between the gastric & colon fluids.
Blood Flow To The GIT
The GIT is extensively supplied by blood capillary network & the
lymphatic system.
The blood flow rate to the GIT is 500 to 1000 times (28% of
cardiac output) more than the lymph flow.
GI perfusion rate could be a rate limiting step in the absorption of
lipid soluble drugs.
The perfusion rate increases after meals but absorption is not
influenced significantly.
Disease States
Classes of diseases states, can affect on Bioavailability of drug
Gastrointestinal diseases
Cardiovascular diseases
Hepatic diseases
Gastrointestinal diseasesAltered GI motility
GI diseases & infectionsAchlorhydria – decreased gastric acid secretion &
increased stomach pHMalabsorption syndrome
Celiac diseaseCrohn’s disease
Infections like gastroenteritis, cholera, colitis, amoeviasis & constipation
GI surgery
Cardiovascular diseases:
CHF influence bioavailability of drug viz.
oedema of intestine,
Decreased blood flow to the GIT & gastric
emptying rate,
Altered GI pH, secretion & microbial flora
Hepatic diseases:
Such as hepatic cirrhosis.
Presynaptic metabolism
(First-pass effects)
Before a drug reaches blood circulation, it has to pass for
the first time through organs of elimination namely the
GIT & liver.
The loss of drug through biotransformation by such
eliminating organs during its passage to systemic
circulation is called as FIRST-PASS METABOLISM
Following system affect on FIRST-PASS METABOLISM
Luminal enzymes
Digestive enzymes
Bacterial enzymes
Mucosal / Gut wall enzymes
Hepatic enzymes
What is gastric emptying? Describe its role in drug absorption
Write a note on factors affecting drug absorption.
QUESTIONS QUESTIONS ASKEDASKED
For further reading regarding this topic, please refer the books like Brahmankar, Remington, Alton and another related books…..!