1.5 Drug Toxicity And Drug Interactions

Question 1

Adverse effects of drugs

Answer 1

• And add first drug reaction is any effect produced by a drug in a patient that is not the intended effect.
• all drugs have potential to cause adverse effects but not all the same

Question 2

Extension of therapeutic effect

Answer 2

–Too much of the drug is in the blood this is what commonly happens in drug overdose.

Question 3

Unrelated to main drug action

Answer 3

• Effects that are unexpected and unrelated to the intended pharmacological action of the drug for example nausea

Question 4

Allergic reaction

Answer 4

Dash mediated by the immune system. An antigen antibody combination provokes an adverse reaction in the patient. The reaction may be very mild like a skin rash or very severe anaphylaxis. Susceptibility to allergic drug reaction may have a genetic component.

Question 5

Drug dependence and addiction

Answer 5

-unwanted physiological and psychological effects of the drug

Question 6

Teratogenesis (birth defects)

Answer 6

Drug produces defects in the developing fetus

Question 7

Adverse bio transformation reactions

Answer 7

Drug is converted to a chemically reactive metabolite that combine to tissue components and cause tissue or organ damage

Question 8

Adverse drug reactions that are difficult to predict - The toxic reaction may be rare

Answer 8

• for example the antibiotic Chloramphenicol was used for several years before it was realize that one in50,000 patients It could cause fatal bone marrow damage

Question 9

The toxic reaction may only appear after the drug has been in prolonged use

Answer 9

– for example when streptomycin was first introduced for the treatment of tuberculosis, it was not realize that it could cause deafness if used for an extended period of time

Question 10

The toxic effect is not detectible in animals

Answer 10

• For example, headache, insomnia, nausea, and mental disturbance will not be readily picked up an animal testing

Question 11

Toxic affect maybe you need to a particular time period

Answer 11

• until it was found thalidomide Produced abnormal limb growth in the fetus, drug testing was not done in pregnant animals. Even if we test new drugs and pregnant animals, the results will not necessarily reflect what occurs in the pregnant human. All new drugs have to be used with very great caution in pregnant women

Question 12

Accessing drug toxicity

Answer 12

• drug toxicity is access by using a Measure called therapeutic index

Question 13

Therapeutic index formula

Answer 13

Therapeutic index = TD50/ ED50

TD- The toxic dose 50. The dose that is toxic in 50% of the population
ED- The effective dose 50. The dose of the drug that is effective and 50% of the population.

Question 14

Therapeutic index

Answer 14

• hired the therapeutic index, safe for the drug. Lower the therapeutic index, it is more likely that toxicities will be observed.

Question 15

Drug-drug interactions

Answer 15

• occurs when one drug changes the pharmacological affect of a second drug
• many patients take several drugs, the elderly, which result in possibility of having drug interactions.
• can occur at many points during the drugs journey throughout the body.

Question 16

Drug- drug interactions in absorption

Answer 16

• when drug can affect the absorption of another drug. For example, a drug can increase intestinal movement, speeding the passage of a second drug through the intestine, decreasing contact of the second drug with the intestinal wall, thereby decreasing absorption

Question 17

Drug- drug interactions in metabolism

Answer 17

• One drug may affect the metabolism of another drug. For example, a drug can block the inactivation of a second drug in the liver, increasing the blood level and pharmacological effects of the second drug.

Question 18

Drug- drug interactions in excretion

Answer 18

• One drug may affect the excretion of another drug. For example, a drug can facilitate the excretion of a second drug by the kidney, decreasing the blood level and pharmacological effect of the second drug.

Question 19

Drug-food interactions

Answer 19

– Involve the interference of food with drugs taken concurrently

Question 20

Thyramine

Answer 20

• found in old cheeses. It is capable of raising blood pressure and his broken down in the liver by an enzyme known as monoamine oxidase (MAO). Usually the thiamine present in foods is not a problem, one class of antidepressant drugs are inhibitors of MAO. If a patient is being treated with an MAO inhibitor and consumes this, retirement will not be broken down in active products in the blood pressure raising effects of thyramine will be greatly intensified

Question 21

Grapefruit

Answer 21

• known to alter the absorption of some drugs.
• A number of drugs are biotransformed and inactivated by drug metabolizing enzymes located in cells in the gastrointestinal tract.
• component of grapefruit inhibits these enzymes, resulting in a greater amount of the active drug being absorbed then would occur without grapefruit.
• The result of this is higher blood levels of the drug than expected, which could potentially lead to overdose. No hospitals in Ontario serves grapefruit products.