PHARMACOKINETICS Flashcards
protein binding
Main plasma protein for binding alkaline drugs?
Main for acidic drugs?
- Alkaline- glycoprotein
- Albumin- acidic
what is transported easily across BBB
higher the lipid-water partition coefficient,,,
unionised molecules that are freely available and less protein bound
,,, greater the ability to cross the barrier
what are circumventricular organs that lack BBB
- subfornical organ
- area postrema of medulla
- median eminance
For a drug to reach steady state it typically takes
5-6 half lives.
CYp enzymes act in endoplasmic reticulum of..
hepatocytes and cells in intestine (why if hepatitis or cirrhosis then affects metabolism)
CYP and …
1. SSRIS -
2 Carbamazepine
3. TCA + haloperidol
- inducers
- inhibiters
- SSRIS - inhibit CYP. fluoxetine increases plasma TCA, fluvoxammine increases plasma clozapine 10X
2 Carbamazepine - decreases plasma conc of drugs eg contraceoptive pills - TCA + haloperidol - compete with each other
- inducers - alcohol, smoking
- inhibiters grapefruit juice, caffeine
what enzymes does smoking and caffeine affect
CYP1A2 + UGT enzyme (glucuronidation reaction)
e.g. clozapine and olanzapine affected
Which enzyme is involved in the aetiology of alcoholic brain damage?
Transketolase - it requires thiamine (vitamin B1) as a co-factor. Chronic alcohol misuse can lead to thiamine deficiency
the least cardiotoxic TCA
Lofeprmaine
BEST antipsychotic in .iver disease
amisulphride
volume of distribution
Vd = amount of drug in the body/concentration in the plasma
antidepressants is associated with a relatively lower incidence of sexual dysfunction?
Reboxetine
weight gain caused by antipsychotic drugs is thought to be mediated, in part, via what mechanism?
Histamine receptor antagonism.
which amtidementia drug is broken down cholinesterase but NO HEPATIC involvement?
Rivastigmine
rivastigmane (it STIG ITS SO fast round the body it misses the liver)
Varenicline MOA
Partial nicotine agonist
alleviates symptoms of nicotine craving and withdrawal
rate limiting step in dopamine metabolis?
Tyrosine hydroxylase
how to swap from MAOI to SSRI?
withdraw and wait 2 weeks before starting
what does carbamazepine increase concentration of?
Phenytoin + clomipramine
alpha 2 agonist medications given to help opiate withdrawal?
Clonidine (more hypotension associated)
Lofexidine
Which antipsyychotic best for hyponatrameia?
clozapine (think salivate lots so reduce vol water = high Na conc)
