Pharmacotherapy

Question 1

What is an agonist and antagonist?

Answer 1

Agonist- stimulates receptors or mimic natural mediators/substrates
Antagonist- blocks receptors or enzymes

Question 2

What are some systemic ways to give a drug?

Answer 2

Oral, buccal sublingual nasogastric, rectal, inhalation, dermal, injection

Question 3

What are some local ways to give a drug?

Answer 3

Oral, topical, vaginal, some injections eg intra-articular

Question 4

What are some patient variability in drug handling?

Answer 4

-Age- young or old may give reduced dosage as reduced liver or renal function
-Genetic- allergy, lactase deficiency, PKU
-Gender
-Body weight/composition
-Drug-drug interaction or drug food
-Comorbidity- pregnancy, tolerance, hypoproteinaemia
-Adherance

Question 5

What are the principles of pharmacokinetics?

Answer 5

1. Liberation- eg disintegration of tablet
2. Absorption- most absorbed in duodenum. Presence of food can affect
3. Distribution- movement of blood between blood circulation and tissues. Proportion of drug between blood/plasma and tissues. Different tissues have different uptakes
4. Metabolism- may be chemically altered by liver by cytochromes. Drugs affected to many different extents. Aim is to render the molecule more hydrophillic.
5. Excretion- injection- straight to distribution
   -main site=kidneys

Question 6

What is the first pass effect?

Answer 6

After oral administration, some of the drug may be extracted and metabolised by the liver- first pass metabolism before getting into the circulation

Question 7

What can affect the bioavailability of an oral drug?

Answer 7

Inadequate liberation, entrainment in food particually fibre which carries it to faeces, incomplete absorption eg GI tract diseases, 1st pass metabolism

Question 8

What are some examples of food-drug interactions?

Answer 8

-Vit C increases iron absorption
-Indoles in cabbage, brocolli can increase metabolism in some drugs
-Grapefruit juice blocks metabolizing enzymes of small intestine- increased bioavailability and thus side effects of some drugs

Question 9

What incompatibilities can occur between drugs and enteral or parenteral feeds?

Answer 9

-Phenytoin- reduced absorption
-antacids- obstructive plug
-theophylline- reduced bioavailability

Question 10

How may drugs affect food and nutrition?

Answer 10

-appetite changes
-taste and smell changes eg amitriptylline
-GI effects- NSAID- inflammation
-nutrient absorption
-vitamin and mineral deficiencies eg diuretics and potassium