Lecture 3 - Drug absorption 1 Flashcards
give the 4 types of injection absorption
- subcutaneous
- intramuscular
- intravenous
- intrathecal
explain drug absorption at the intestine
by PASSIVE transfer rate determined by the ionisation and lipid solubility of drug molecules (pH 7 to 8)
what are the main factors that affect GI absorption of drugs?
- GI motility
- splanchnic blood flow
- particle size and formulation
- physicochemical factors
give the decresed and increased absorption of drugs for coeliac disease
v absorption- thyroxine and digoxin
^ absorption propranolol, cotrimoxazole + cephalexin absorption
few examples where food increases drug absorption
- propanolol
____ drugs (e.g., Metoclopramide) → Speed up gastric emptying, affecting absorption.
Muscarinic
give and example of drugs acting locally in gut and not getting absorbed
-vancomycin
treats c.difficile colitis by staying in gut
- mesalazine
used for crohns disease,
- olsalazine (acid dimer) activated by colonic bacteria
what do Tetracycline + Calcium do
→ Forms insoluble complex, so the drug can’t be absorbed - Cholestyramine + Warfarin/Thyroxine → Binds these drugs in the gut, blocking absorption shopuld be taken separatly
what is completely inactivated by gastric acid and proteolytic enzymes?
Benzylpenicilin
insulin
what metabolises monoamines
gut wall by MONOAMINE OXIDASES
what is the most important site for 1st past metabolism ?
th liver
give an example of low intermediate and high hepatic extraction ratio
low - cloramphenical
intemetiate - aspirin
high - chloromethiazole
define systemic avilability
amount of drug reaches systemic cirulation intact
what does the rate of sytemic avalibility depend on ?
- pharmaceutical factors
- gastronintestinal absorption
- pre-systemic metagoblism relatively unimportant
what does the extent of availibility depend on?
- extent of absorption and extent of pre-systemic metabolism
when is differences in absorption profile important for some drugs ?
analgesics
sublingual glyceryl trinitrate
what is the problem and result of transdermal drug delivery ?
- variability in drug administration through skin —–results - lack of presicion regarding real dose absorbed
Ointments containing ______ require
multiple application per day
nitroglycerine
give 2 reasons transdermal needed
- Troublesome side-effects or unreliable therapeutic action
with repetitive dosing with conventional dosage forms, - Patient compliance difficulties,
- Need for frequent dosing in conventional dosage forms
because of the drug’s short biological half-life - Gastric irritation with oral therapy
describe scoplolamine
applied to skin- drug moves slowely following CONC GRAD
no extra energy needed
steady drug release. as long as extra drug in resevoire
give an exmaple of scoploamine
- nicorette
what is the main site of absorption
small intestine
