Sympathomimetics Part 2 (Direct Agonists)

Question 1

What are the characterisitics of Epinephrine?

Answer 1

1. Potent stimulator of all adrenergic receptors.
2. Released by adrenal medulla
3. Inactivated by the liver
4. Converts energy stores to useable fuels.

Question 2

What some vascular effects of Epinephrine?

Answer 2

1. Contraction of vessels
2. Increased venous tone
3. Increased skeletal muscle blood flow.

Question 3

What are some non-vascular smooth muscle effects of Epinephrine?

Answer 3

1. Relaxes GI smooth muscle

2. Bronchodilation

Question 4

What are some therapeutic uses of Epinephrine?

Answer 4

1. Relief of hypersensitivity reactions
2. Prolong effects of local anesthetics
3. Hemostatic agent
4. Asthma

Question 5

What are some side effects of Epinephrine?

Answer 5

1. Headache
2. Restlessness
3. Tremors
4. Palpations.

Question 6

What are some characteristics of NE?

Answer 6

Increases TPR and Blood pressure

Question 7

Describe how the potency of phenylephrine can be changed.

Answer 7

Without the -OH group at 4 position on the benzene ring, phenylephrine is less potent than Epi. The abscene of the -OH groups increases bioavailability after oral intake, prolongs duration of action and increases its ability to pass the BBB.

Question 8

What is Phenylephrine’s uses? Side effects?

Answer 8

Use: Maintain blood pressure during anesthesia
Toxicity: Rebound nasal congesition, headache and insomnia

Question 9

Discuss Midodrine (a1)

Answer 9

A prodrug that is hydrolzyed into desglymidodrine, the actual adrenoreceptor agonist. Treats orthostatic hypotension
Toxicity: Supine hypertension, urinary retention.

Question 10

Discuss Clonidine (a2)

Answer 10

Treats hypertension and withdrawal from abused drugs. Inhibits adenylyl cyclase.
Side effects: Dry mouth and sedation.

Question 11

Discuss Isoproterenol (B1, B2)

Answer 11

Stimulates heart (B1); Vasodilator (B2). Toxic to patients with coronary heart disease. 
Side effects: palpitations, tachycardia, headache and flushing.

Question 12

Discuss Dopamine (B1)

Answer 12

Different effects depending on dose.
Low: Increase in renal blood flow
Moderate: Release of NE from nerve terminals
High: Vasoconstriction
Used for CHF with hypotension

Question 13

Discuss Dobutamine (B1)

Answer 13

Treats cardiogenic shock; Does not increase renal blood flow, cause vomiting or release NE

Question 14

What does a B2 receptor agonist do?

Answer 14

Interferes with release of inflammatory mediators and relaxes bronchial smooth muscle. (Albuterol)

Question 15

What is the difference between salmeterol and albuterol?

Answer 15

Salmeterol has a slow onset and a long duration of action. Metabolized by CYP34A and eliminated in feces.

Question 16

Which drugs should be administered for acute hypotension?

Answer 16

Direct acting alpha adrenoceptor agonists: NE or phenylephrine.

Question 17

Which drugs should be used to treat cardiogenic shock?

Answer 17

A beta -1 agonist: Dopamine or Dobutamine

Question 18

Which drugs should be used for emergency cardiac arrest or heart block?

Answer 18

Epinephrine or Isopreteronol

Question 19

Which drug should be used for Hypertension? Orthostatic hypotension?

Answer 19

Hypertension: Clonidine

Orthostatic Hypotension: Midodrine