Pharmacokinetics

Question 1

What are the 4 pharmacokinetics processes ?

Answer 1

• absorption
• distribution
• metabolism
• elimination

Question 2

What factors affect drug absorption?

Answer 2

• food
  -formulation
• pH of blood
• site of absorption
• GI motility
• pre-existing medical conditions

Question 3

If the route of administration is oral, where is the site of absorption?

Answer 3

mouth & GI tract

Question 4

If the route of administration is sublingual, where is the site of absorption ?

Answer 4

under tongue

Question 5

If the route of administration is buccal, where is the site of absorption ?

Answer 5

oral mucosa

Question 6

If the route of administration is intra-ocular , where is the site of absorption ?

Answer 6

eyes

Question 7

What factors affect drug distribution ?

Answer 7

• plasma protein binding
• specific drug receptor sites in tissues
• regional blood flow
• lipid solubility
• disease

Question 8

What are drugs are 95% bound ?

Answer 8

• thyroxine
• warfarin
• diazepam
• heparin

Question 9

What drugs are between 90-95% bound ?

Answer 9

• phenytoin
• propanolol

Question 10

What are some factors which can increase the fraction of unbound drug?

Answer 10

• renal impairment
• low plasma albumin levels
• late pregnancy
• displacement from binding site by other drugs

Question 11

What factors affect drug metabolism ?

Answer 11

• ‘First pass’ effect
• hepatic blood flow
• liver disease
• genetics
• other drugs
• age

Question 12

Where is the main site of drug metabolism ?

Answer 12

the liver

Question 13

Describe the ‘first pass; metabolism

Answer 13

• drugs absorbed from GI tract into blood stream
• blood travels immediately to liver
• some drugs are inactive 1st time they pass through liver

Question 14

What ages results with impaired hepatic enzyme activity ?

Answer 14

• elderly
• children <6 months - especially premies

Question 15

Describe enzyme inducing drugs

Answer 15

• enhance the production of liver enzymes which break down drugs
• faster rate of drug breakdown
• larger dose of affected drug needed to get same clinical effect

Question 16

What are some examples of enzyme inducing drugs ?

Answer 16

• phenytoin
• phenobarbitone
• rifampicin
• smoking & chronic alcohol intake

Question 17

Describe the enzyme inhibiting drugs

Answer 17

• inhibit the enzymes which break down drugs
• decreased rate of drug breakdown
• smaller dose of affected drug needed to be produced the same clinical effect

Question 18

What are some examples with enzyme inhibitors ?

Answer 18

• erythromycin
• oral contraceptives
• omeprazole

Question 19

What facts affect drug excretion ?

Answer 19

impaired renal function = impaired drug excretion

Question 20

Where is the main site of drug excretion ?

Answer 20

kidneys
but drugs can also be excreted via bile, sweat, lungs, breast milk, saliva

Question 21

What does renal drug elimination depend on?

Answer 21

• blood flow to kidney
• glomerular filtration rate
• urine flow rate & pH which indirectly alter passive reabsorption & active tubular secretion

Question 22

Define half life

Answer 22

= time required to reduce the plasma conc. of a drug to half of its original value & is usually measured in hours