Peripheral Vasodilators

Question 1

Classification of peripheral vasodilators?

Answer 1

1. ALPHA BLOCKERS
2. PHOSPHODIESTERASE INHIBITORS
3. PROSTAGLANDIN ANALOGUES
4. PLANT DERIVATIVES
5. HISTAMINE ANALOGUES
6. CALCIUM CHANNEL BLOCKERS

Question 2

Explain the Alpha blockers?

Answer 2

Function to block the alpha 1 receptors, can be selective and non-selective (own features)

1. Non-selective Alpha Blockers:
   (NICERGOLIN) - functions to cause peripheral vasodilation, relaxation of bladder sphincter and relaxation of the uterus. Good oral absorption aside from 50% FPM, low bioavailability, wide distribution with BBB-BPB penetration. Hepatic metabolism and urinary excretion.
2. Selective Alpha Blockers: (PRAZOSIN) - Only block alpha 1 receptors and nothing else. Again causes peripheral vasodilation, bladder sphincter relaxation and uterine relaxation. Good oral absorption, significant FPM. Hepatic metabolism and bile/urinary excretion.

Question 3

Explain Phosphodiesterase Inhibitors?

Answer 3

They are non-selective and selective, have the general effects of increasing in cAMP and cGMP (stimulate vasodilation) levels on blockage of “PDE receptors”.

1. Non-selective: (PAPAVERINE and PENTOXYFYLLINE) - inhibits all types of PDE receptors. Spasmolytic effect in bronchial, biliary, GI and urinary tracts. Pentoxifylline: increase RBC flexibility, decrease platelet aggregation and increase fibrinolysis. Good oral absorption, BBB-BPB penetration. Hepatic metabolism and urinary excretion. ADE’s hypotension and tachycardia.
2. Selective: (SLIDENAFIL-VIAGRA) which blocks type 5 PDE inhibitors. Vasodilation due to increased cGMP and nitric oxide. Good oral absorption, extensive FPM, Hepatic metabolism and urinary excretion. Used for the treatment of erectile dysfunction and pulmonary hypertension. ADE’s Hypotension and vision impairment.

Question 4

Explain Prostaglandin analogues?

Answer 4

PGI2 analogues cause vasodilation (EPOPROSTEROL / ILOPROST). Good oral absorption and may be IV infusion. Tissue metabolism (not hepatic) and excretion in both urine and feces. Used for the treatment of pulmonary hypertension, erectile dysfunction and peripheral vasodilation. ADE’s flushing, fainting, hypotension and headache.

Question 5

Explain Plant Derivatives?

Answer 5

(VINOPECTIN / GINKO BILBOBAE) Ginko bilbobae produces NO. Used for cerebral selective vasodilation. Improves cerebral metabolism. Therapeutic use: improve learning and memory. ADR’s: tachycardia and hypotension.

Question 6

Explain Calcium channel blockers?

Answer 6

CINNARIZINE / FLUNARIZINE , function to block cerebral calcium channels. Functions to reduce the frequency of migraine attacks + Antivertigo
effect. Therapeutic use: migraine and improve learning and memory

Question 7

Explain Histamine Analogues?

Answer 7

BETAHISTINE
Agonist for H1 receptors (stimulates vasodilation)
PhD: antivertigo effect by acting on the labyrinth of the inner ear
Therapeutic use: vertigo