mix-acting/Indirect-acting adrenergic agonists

Question 1

Define Mix-Acting Adrenoceptor agonists

Answer 1

• Indirectly release norepeinephrine and also directlya ctivate adrenoceptors
• ex: EPHEDRINE

Question 2

EPHEDRINE (ephedrine, ephedra)

Answer 2

MIXED-ACTING AGONISTS

• has HIGH bioavailability and a relatively long duration of ation
• MILD CNS STIMULANT
• Pseudoephedrine is used as decongestant

**Respnose IS REDUCED BY PRIOR TX with RESERPINE or GUANETHIDINE

Question 3

EFFECTS OF AMPHETAMINE

Answer 3

EFFECTS: Indirect acting releasing agent Agonist

• CNS

–> release biogenic amines from storage sties in nerve terminals

–> stimulates the medullary respiratory centers

–> stimulates cortex and reticular activation system –> PREVENTS FATIGUE, DELAYS NEED FOR SLEEP

–> tx obesity (decrease food intake)

• Cardiovascular effects:

–> activates peripheral ALPHA AND BETA

–> increase systolic and diastolic BP

–> increase HR

• SMOOTH MUSLCE: INCREASE bladder sphincter contraction –> tx enuresis and incontinence

Question 4

TYRAMINE

Answer 4

INDIRECT ACTING Releasing agent agonist

• Used to synthesize NE and EPI via alternative pathway
• destroyed by MAO in the gut wall and liver
• action INCREASES BY MAO INHIBITION –> ingesttion of tyramine-rich foods (fermented cheese –> sudden and dangerous rise in blood pressure)
• NO CNS effects

Question 5

describe the mechanism of action of amphetamine type amines

Answer 5

• structurally relate to NE –> transported by NET1
• displace NE –> NE release independent of exocytosis
• Activity affect by Rx affecting storage (reserpine, MAOI, NET1 inhibitors)