pharmacokinetics

Question 1

PROCESS INVOLVED IN PHARMACOKINETICS

Answer 1

absorption
distribution
biotransformation (metabolism)
Excretion

Question 2

Factors affecting drug absorption?

Answer 2

1)Drug Characteristics- Drug formulation
Drug Conc (direct relation), Lipophilic (non-ionized) and hydrophilic (ionized), acidic/alkaline;
2)Routes of administration
3)Blood flow
4)Cell membrane characteristics-passive diffusion/ active transport

Question 3

drug absorption in the blood is reduced in which medical conditions?

Answer 3

patients suffering from Chronic Heart Failure or any heart condition that affects blood flow

Question 4

Routes of administration, site, and the time required -

Answer 4

Oral-30 mins-duodenum
IV-BLOOD-instant-(100% BIOAVAILABILITY;titrated)
IM-5 mins-upper lateral quadrant of gluteal muscle; young children-anterior thigh
Inhalation-5 mins;titrated
SC-15 mins
Patch- abt 15mins

Question 5

Emergency drug? and its dosage in IV and SC

Answer 5

Epinephrine
IV- 1/10,000
SC- 1/1000

Question 6

Factors that affect bioavailability?

Answer 6

1)Route of admin
2)drug degradation before absorption
3)drug formulation
4)GI Perfusion and ph
5)binders and dispersing agents in the GI tract
6)GI absorption
7)Solubility-hydrophobic(plasma membrane);hydrophilic(kidney excretion)
8) Hepatic first-pass effect

Question 7

is oral bioavailability in geriatric pts affected? why?

Answer 7

acidic for absorption; as we age stomach alkaline ph > hence difficulty in absorption

Question 8

what is the Hepatic first-pass effect?

Answer 8

drug absorption-partly-portal vein-liver -metabolized-circulation-kidney-excreted

Question 9

types of passive transfer

Answer 9

Simple passive diffusion-lipid soluble only-no energy-no carrier-down conc gradient…

Question 10

properties that influence the passage of drugs across membranes

Answer 10

Lipid solubility
degree of ionization
molecular shape and size

Question 11

criteria to cross BBB

Answer 11

Only lipid-soluble,
non-ionized compounds

Question 12

eg of drug easily crossing BBB and inducing sleep

Answer 12

thiopental - IV

Question 13

which factors affect the drug distribution?

Answer 13

Rate of blood flow to the tissue
protein binding
permeability-cross bbb
Gastric emptying time

Question 14

which plasma protein has the highest ability to bind to drugs?

Answer 14

Albumin

Question 15

what is biotransformation

Answer 15

catalytic chemical alteration of nonpolar(lipid soluble)drug to polar(lipid insoluble) or water-soluble compound to be easily excreted out through the kidney

Question 16

effects of biotransformation on drugs

Answer 16

inactivation of the drug or its metabolite
formation of active metabolite from active drugs
activation of inactive drug

Question 17

_ drug is metabolized to an active drug/metabolite?

Answer 17

codeine (inactive drug) to morphine (active metabolite)

Question 18

eg of active metabolite to active drug

Answer 18

diazepam( desmethyldiazepam also known as nordazepam or nordiazepam), codeine - morphine, Imipramine - desipramine

Question 19

Activation of inactive drugs

Answer 19

prodrugs

Question 20

examples of prodrugs

Answer 20

Levodopa (inactive ) to Dopamine (active)
Prednisone (inactive) to Prednisolone (active) - corticosteroids in autoimmune condition

Question 21

levodopa is the drug of choice in

Answer 21

management of Parkinson

Question 22

which enzyme is responsible for the phase 1 reaction of metabolism, Located in? and state types of reaction in Phase 1?

Answer 22

CY P-450 - liver microsomal enzyme -liver hepatocytes
Oxidation->hydroxylation, reduction and hydrolysis

Question 23

CY P-450 dependant and independent oxidation includes which process with examples of each

Answer 23

CY P450 DEPENDANT
*Aromatic hydroxylation -
R R
⏣ -> ⏣
OH
Phenobarbitone (pheno
propranolol proposed
phenytoin pheny
amphetamine amid
warfarin war)

*Oxidative N-dealkylation - morphine
RNHCH3 -> RNH2

CY P450 INDEPENDENT
RCH2NH2 -> RCHO
*amineoxidase
*adrenaline

Question 24

phase I reduction- EG AND REACTION

Answer 24

Reduction
RCR’ RCHR’
II -> I
O OH
methadone
naloxone

Question 25

HYDROLYSIS REACTION AND COMPOUND

Answer 25

HYDROLYSIS
R1COOR2 -> R1COOH + R2OH

Question 26

phase II PROCESS and important reactions

Answer 26

Conjugation - responsible for making drug hydrophilic
types
Glucuronide
acetyl
glutathione
glycine
sulphate
methyl

Glucuronidation,acetylation or sulfation

Question 27

P450 inducers- causes and examples

Answer 27

lower drug efficacy
-rifampicin
-Phenytoin
-Phenobarbitol
-St. John Wort
-Carbamazepine
-Chronic alcohol abuse

Question 27

P450 inhibitors- causes and examples

Answer 27

higher drug efficacy and risk of toxicity
-cimetidine
-ketoconazole
-Grapefruit juice
-Macrolide antibiotics
-Acute alcohol intake

Question 27

Drugs completely metabolized by the liver

Answer 27

lignocaine, glyceryl trinitrate

Question 28

Factors affecting hepatic first-pass metabolism

Answer 28

1. Microsomal enzyme inhibition
2. Microsomal enzyme inducer
3. plasma protein binding
4. genetic factors
5. liver disease

Question 29

——– Genetic decreases the efficacy of codeine and its effects

Answer 29

CYP2D6 genetic polymorphism-rapid metabolization of codeine to morphine leading to toxicity and respiratory depression
contraindicated in children below 12

Question 30

which drug decreases the clearance of warfarin by —- and causes —-

Answer 30

metronidazole; 40%

Question 31

what kind of compounds are excreted by lungs and eg

Answer 31

Volatile:-
N2O ,
hurane,
isoflurane
halothane

Question 32

Zero-order elimination and eg

Answer 32

elimination of drugs in a linear constant
eg alcohol, phenytoin and aspirin -at high or toxic doses

Question 33

first-order elimination with eg

Answer 33

elimination of drugs in proportion to drug conc
eg Drug half-life -takes 4 half-lives to eliminate drugs