Pharmacology Practicals

Question 1

How does tropicamide cause pupil dilation?

Answer 1

• Blocks muscarinic receptors in the eye

- This blocks the response of the sphincter and ciliary muscles to cholinergic stimulation, resulting in pupil dilation

Question 2

How does pilocarpine cause pupil constriction?

Answer 2

• Cholinergic parasympathomimetic

- Causes contraction of the iris sphincter muscle and ciliary muscle by stimulating muscarinic receptors

Question 3

List the sympathetic sites in the eye

Answer 3

• Ciliary body
• Radial muscles
• Capillaries
• a1 receptors

Question 4

List the issues with drugs applied topically to the eye

Answer 4

• The eye is difficult to penetrate, and it can be hard to know the exact dosage due to possibility of the drop coming out if the eye, or having to apply a second drop
• Can get into the systemic circulation once absorbed
• Dipivefrine - can cause hypertension
• Timolol - can slow the heart rate and reduce cardiac output, and causes bronchoconstriction as well as hypoglycaemia

Question 5

How does heroin cause pupil constriction?

Answer 5

• Heroin causes disinhibition of the oculomotor nerve

- In long term use asphyxia can occur causing permanently small pupils

Question 6

How do organophosphates cause pupil constriction?

Answer 6

By blocking acetylcholine breakdown, so therefore acetylcholine will be longer acting.

Question 7

How are prostaglandin analogues useful in glaucoma treatment?

Answer 7

• Improves drainage of aqueous humour

- Alter collagens to decrease the resistance to uveoscleral outflow from the ciliary body

Question 8

How are carbonic anhydrase inhibitors used in glaucoma treatment?

Answer 8

• Decrease aqueous humour production

- Carbonic anhydrase is linked to beta 1 adrenoceptors

Question 9

Compare secondary and primary glaucoma

Answer 9

• Secondary glaucoma is intraocular pressure of more than 20mmHg found in the presence of ocular disturbance
• Eg. trauma, neoplasma, steroid administration
• Primary glaucoma is where there is no evidence of a cause of secondary glaucoma. There are 3 types

Question 10

List the sympathetic affects on the blood pressure

Answer 10

• Heart (beta 1 receptors in the SA node are chonotrophic, while in the cardiac muscle they are ionotrophic)
• Vasculature (alpha 1 receptors cause vasocostriction of the GI vessels, and beta 2 causes vasodilation)
• Kidney (beta 1 receptors stimulates renin angiotensin system)

Question 11

Where does pindolol act?

Answer 11

Blocks beta 1 receptors in the heart and kidney

Question 12

What type of beta blockers are cardioselective?

Answer 12

Beta 1 selective as they mainly affect the heart