7 - Aspirin

Question 1

What effect does aspirin have on platelets? How is this achieved?

Answer 1

• Aggregation inhibition
• Reduces adhesive properties of platelets
• Aspirin interferes w/ production of thromboxane A2

Question 2

How does aspirin interfere w/ production of prostaglandins? What does this cause?

Answer 2

• Acetylation of COX enzyme

- Causes aspirin to avert the sensitization of pain receptors

Question 3

How does aspirin have antipyretic activity?

Answer 3

Interferes w/ production of prostaglandin E2 in the brain

Question 4

Most common adverse effect of aspirin

Answer 4

Stomach upset

Question 5

How is aspirin made?

Answer 5

• Salicylic acid and acetic anhydride by esterification

- Involves sulfuric acid as a catalyst

Question 6

Which limit tests are required on aspirin based on USP guidelines?

Answer 6

• Chloride
• Sulfate
• Heavy metals
• Free salicylic acid

Question 7

How should tubes be viewed for colour comparison?

Answer 7

Downward against a white background w/ light source directed from beneath the bottom of the tubes

Question 8

How should tubes be viewed for turbidity comparison?

Answer 8

Horizontally against a dark background w/ light source directed from side of the tubes

Question 9

What is the basis for the chloride limit test? What is compared? What are the results for a pass?

Answer 9

• Precipitation of chloride w/ silver nitrate in the presence of dilute nitric acid
• Compare opalescence of sample and standard after 5 minutes
• Test shouldn’t have more chloride than that of 0.10 mL of 0.02 N HCl (0.014%)

Question 10

What is the basis for the sulfate limit test? What is compared? What are the results for a pass?

Answer 10

• Precipitation of sulfate w/ barium chloride in the presence of HCl and traces of barium sulfate
• Compare opalescence of sample and standard after 10 minutes
• Test shouldn’t have more sulfate than that of 1.25 mL of 0.02 N sulfuric acid

Question 11

What is the basis for the heavy metals limit test? What is compared? What are the results for a pass?

Answer 11

• Colour change between various metallic impurities and sulfide ion
• Compare colour of test and standard at the interface (top layer) after 5 minutes
• Test sample must not be darker than that of the lead standard

Question 12

What is compared for the free salicylic acid limit test?What are the results for a pass?

Answer 12

• Compare colour of the test and standard after 30 seconds

- Colour in test sample is not more intense than that of solution of 0.1% salicylic acid

Question 13

Which metals will typically respond to the limit test for heavy metals?

Answer 13

• Lead
• Mercury
• Bismuth
• Arsenic
• Antimony
• Tin
• Cadmium
• Silver
• Copper
• Molybdenum

Question 14

What is found in an aspirin effervescent tablet?

Answer 14

• Aspirin
• Effervescent mixture of organic acid (commonly citric acid) and alkali metal bicarbonate and/or carbonate (ex: sodium bicarbonate)

Question 15

What is considered a pass for the test of effervescent tablets?

Answer 15

Should dissolve completely in 100 mL of water at room temperature w/in 5 minutes

Question 16

Purpose of enteric coated aspirin tablets?

Answer 16

Minimize irritation on gastric mucosa

Question 17

Why do enteric coated tablets dissolve in the small intestine?

Answer 17

• Higher pH (above 5) so coating will become ionized and soluble
• Remain unionized at lower pH of stomach

Question 18

What is considered a pass for the test of enteric coated tablets?

Answer 18

• No disintegration in stomach pH

- Disintegration in small intestine pH w/in 15 minutes