Revision Questions

Question 1

Explain the effects of a receptor mediated drug within the body

Answer 1

The drug is known as an AGONIST (or receptor mediated)

as it mimics the action of the body’s own chemicals at appropriate receptor sites.

Question 2

Explain the effects of a non-receptor mediated drug within the body

Answer 2

A Non receptor mediated drug (antagonist) combines with receptor sites, but fails to initiate a response

Question 3

Explain how a drug is distributed to its destination site

Answer 3

After a drug is absorbed it passes through various body fluids.

It passes to the blood plasma, into interstitial fluid where some molecules attach to the cell membrane, trans-cellular fluid and then into the intracellular fluid

Question 4

Explain how amoxicillin is metabolised by the liver.

Answer 4

The liver produces enzymes that transform drugs into water-soluble metabolites that can be passed in the urine.

Some highly lipid soluble drugs are incorporated into bile and eliminated via the biliary system.

Biotransformation (metabolism) usually occurs in two phases:

Phase 1: The original molecule is transformed by a process of oxidation,
reduction or hydrolysis.

Phase 2: The enzymes, conjugate the phase 1 metabolite with another molecule e.g. glucuronic acid, sulphate or glycine to produce a hydrophilic molecule.

The liver excretes drugs by first incorporating them into the bile, which is then passed into the small intestine. Once it reaches the small intestine, it will either be passed in the faeces or in some cases it can be reabsorbed into the blood stream.

Question 5

Biotransformation (metabolism) Phases

Answer 5

Phase 1: The original molecule is transformed by a process of oxidation,
reduction or hydrolysis.

Phase 2: The enzymes, conjugate the phase 1 metabolite with another molecule e.g. glucuronic acid, sulphate or glycine to produce a hydrophilic molecule.

Question 6

Why is asprin toxic to cats

Answer 6

Cats have a decreased ability to metabolise drugs like aspirin as they have a reduced ability to form glucuronic acid. This is why it is so toxic to cats.

Question 7

Explain the role of the kidney in the process of metabolism and excretion of Frusemide.

Answer 7

Frusemide is a loop diuretic and exerts its effect on the Loop of Henle in the kidney.

It causes diuresis by inhibiting the re-absorption of sodium from the Loop of Henle.

As sodium is retained in the urine, water is also retained.

At the level of the distal convoluted tubule potassium is exchanged for sodium so some sodium is absorbed back into the body while potassium is excreted.

Because osmotic pressure of urine stays the same, the water stays in the urine and is excreted from the body along with the potassium. It works by decreasing oedema.

There are two ways in which the kidneys excrete drugs:

Glomerular filtration: The glomerulus in the kidney filters drug molecules out of the blood into the glomerular filtrate, which is then eliminated as urine.

Tubular secretion: The kidney tubule cells secrete metabolites out of the capillaries surrounding the tubule and into the glomerular filtrate, which then becomes urine.

Question 8

Explain the two ways in which the kidneys excrete drugs

Answer 8

Glomerular filtration: The glomerulus in the kidney filters drug molecules out of the blood into the glomerular filtrate, which is then eliminated as urine.

Tubular secretion: The kidney tubule cells secrete metabolites out of the capillaries surrounding the tubule and into the glomerular filtrate, which then becomes urine.

Question 9

Describe how phenobarbital acts on the body in the case of epilepsy.

Answer 9

It acts by decreasing the spontaneous depolarisation of brain cells or preventing the spread of depolarisation resulting in a milder fit than would normally occur without the treatment.

Question 10

Describe the formulation of a capsule

Answer 10

Contain granules or powders contained in a hard outer case made of gelatine.

The case comes in two halves that slot together. Some have different size granules so they can dissolve at different rates

Question 11

What precautions should be taken when handling and administering a cytotoxic drug?

Answer 11

Preparing and administering the drug in a well ventilated area away from human traffic

Wearing protective clothing ie: goggles, high efficiency filter mask, a non porous long sleeve gown with tight cuffs and a double pair of latex gloves.

Pregnant women must not handle cytotoxic drugs.

Question 12

Explain the mode of action of meloxicam.

Answer 12

Meloxicam is a non steroidal anti inflammatory drug for use in dogs.

It is used to alleviate inflammation and pain in both acute and chronic musculo-skeletal disorders

Question 13

Explain the mode of action of amoxicillin.

Answer 13

It is a broad spectrum antimicrobial drug which is bacteriocidal in action,
which means that it kills the bacteria.

The mode of action is that they prevent cross-linking of bacterial cell walls.

Question 14

Explain how a dead (killed) vaccine elicits a response in the animals body.

Answer 14

The organisms are unable to reproduce and are therefore incapable of
causing disease.

They provide a weak immune response of shorter duration
and often require large doses to give protection.

Question 15

Describe the characteristics of ivermectin.

Answer 15

Ivermectin acts by enhancing the actions of certain compounds in the body, which inhibits nervous transmission.

NOTE: Ivermectin can produce adverse reactions in collies and collie cross dogs. Can be fatal.

Question 16

Explain the terms bacteriocidal and bacteriostatic.

Answer 16

Bacteriocidal means that the drug kills the bacteria and bacteriostatic means that it stops the bacteria from multiplying.

Question 17

Describe the two ways in which an orally administered drug reaches the site of action.

Answer 17

Selective: Substances, which the body particularly wants, for example amino acids, are carried across the membrane by an energy consuming mechanism.

This can occur against a concentration gradient i.e. from an area of low concentration of substance within the bowel to an area of high concentration within the cells. Some drugs, because of their resemblance to naturally occurring substances, use these existing transport mechanisms.

Non Selective: The substances pass through the membrane from an area of high concentration within the bowel to an area of low concentration within the cells.

Question 18

Describe 6 factors that affect absorption of a drug.

Answer 18

Chemical nature: The acid in the stomach breaks down some drugs, whilst intestinal enzymes digest others. Such drugs can only be given by injection.

Solubility: Drugs given in solution are more rapidly absorbed than those in solid forms. Also local conditions at the site of absorption can alter drug solubility. For example, stomach acid can cause precipitation of the drug, which will slow the rate of absorption.

Concentration: High concentrations of drugs are absorbed more rapidly than low concentrations.

Bowel Movement: Most drugs are absorbed from the upper part of the small intestine and alteration of the gut motility can influence drug absorption e.g. diarrhoea.

Food: Dilution of the drug by food and drink can lead to slowing of absorption.
Formulation: A liquid will be more rapidly absorbed than a solid medicine

Question 19

Intramuscular Injection

Answer 19

Route: An injection into the muscle eg: quadriceps, lumbar, neck muscles

Technique: Prepare injection as prescribed by the veterinary surgeon. Make sure any air bubbles are expelled. Isolate the area for injection (for example the lumbar muscles in the dog) Insert the needle into the muscle at a right angle to the muscle and pull back on the plunger slightly. If no blood appears, administer the injection. Remove the needle and rub the site gently to aid distribution and reduce the stinging sensation.

Advantage: Can be used for relatively irritant drugs. Drugs that are not true solutions i.e. are suspensions can be given this way.

Drugs that cannot be administered subcutaneously because the absorption rate would be too slow. Rapid onset of action 20-30 minutes. Good for injecting a cat if you can’t access a vein.

Disadvantage: Can be painful. Can only administer a certain amount of
drug into one muscle, may have to use two sites. May damage a nerve or
inject into a vein by accident.

Question 20

Non-steroidal anti-inflammatory drugs (NSAIDs)

Answer 20

These inhibit the formation of prostoglandins which are mediators of acute inflammation

Use:

They reduce pain and swelling after surgery
or in joint conditions such as osteoarthritis

Question 21

Tranquilisers

Answer 21

Generally reduces anxiety and produces mental relaxation. They are used to calm the patient down prior to handling or transport.

Question 22

Opioid analgesics

Answer 22

Analgesic drugs reduce the sensations of pain without a reduction in other sensations

potent analgesics

often used with a pre-anaesthetic agent or GA to reduce need for other anaesthetic agents

Mode of action: bring about effects by attaching to opiod receptors in the CNS, GI tract, urinary tract and smooth muscle

Question 23

Opioid analgesic mode of action

Answer 23

Mode of action: bring about effects by attaching to opiod receptors in the CNS, GI tract, urinary tract and smooth muscle

Three main receptors:

Mu receptors - found in the brain responsible for analgesia and euphoria (but also resp depression, hypothermia)

Kappa receptors- analgesia and miosis without resp depression

Sigma receptors - responsible for dysphoria/hallucinations

Question 24

What receptors should a good opioid contain

Answer 24

strong kappa receptor, some mu receptor activity but very little effect on sigma receptors

Question 25

Buprenorphine

Answer 25

Vetergesic

Strong analgesic

has a 1 - 1.5 duration

less potent than morphine can be used in combination with a sedative/tranquiliser

Question 26

Diazepam

Answer 26

aka valium

Diazepam is used in emergency cases to control seizures.

Mode of action - it acts by quieting the activity of the CNS.

sometimes used as an appetite stimulant in cats

Question 27

Mydriatics and Miotics

Answer 27

Mydriatics - causes dilation of the pupil, reducing spasms of the ciliary e.g. atropine

Miotics - causes constriction of the pupil. Will increase drainage of occular fluid. Used to treat glaucoma.

Question 28

Live Vaccine

Answer 28

Consists of living organisms - a slightly different strain to those which cause the disease.

They do not cause the disease but illicit a long lasting immune response

This is because the organism multiplies inside the body after administration of the vaccine.

Question 29

Inactivated Vaccine

Answer 29

aka dead vaccine

will stimulate an immune response to the antogen but do not multiply in the hosts body.

short immune response. Can be used in pregnant animals.

Question 30

Cytotoxic drug safety

Answer 30

Prepare and administer the drug in a well ventilated area away from traffic.

PPE e.g. googles, double pair of latex gloves over a long sleeved gown, hat, high efficiency filter mask

Pregnant women, women of child bearing age should not handle.

Question 31

Explain the mode of action of anthelmintic drug fenbendazole

Answer 31

broad spectrum anthelmintic drug

kills immature larvae stages of roundworm

exerts mode of action by stopping the cells of the worm absorbing glucose this starves the worm to death