A simple, quick and on the go revisable presentation of Alpha 1 SAR. Please do refer other proper reference and study books. This presentation is only for revision purpose.

1. SAR of α-Blocker
Presented by:
Anup Nivrutti Shelke
Institute of Pharmacy
MET BKC
Nashik-03

2. Introduction
Agonist:
• An agonist is a chemical that binds a receptor and activates the receptor to produce a
biological response.
Antagonist:
• an antagonist is chemical that binds to the receptor to block the action.
• It acts opposite to that of agonist
Types of Antagonist
Beta Blocker
1. Beta (ß) 1
2. Beta (ß) 2
3. Beta (ß) 3
Alpha(α) Blocker
1. Alpha(α) 1
2. Alpha α) 2

3. Therapeutic uses of Alpha Blocker
• Treatment of Hypertension.
• Though alpha blockers are commonly used to treat high blood pressure, they're
typically not the first treatment option. Instead, they're used in combination with
other drugs, such as diuretics, when your high blood pressure is difficult to control.
• Vasoconstriction
• BPH
• Raynaud's Disease
• Pheochromocytoma
• CHF
• Erectile Dysfunction

4. • Classification
• Selective
e.g. Prazosin, Terazosin
• Non-Selective
1. Reversible
E.g.: Tolazoline and Phentolamine.
2. Irreversible
E.g.: Dibenamine & Phenoxybenz-amine.
Prazosin
Tolazoline
Dibenamine

5. Non selective alpha one blockers
• These are non selective
• It will bind to the both alpha-1 & alpha-2 receptors.
• These are Imidazoline competitive –blockers and primarily of historical interest. The
structure of Tolazoline are similar to the Imidazoline 1-agonists, but does not have the
lipophilic substituents required for agonist activity. The type of group attached to the
imidazoline ring thus dictates whether an Imidazoline is an agonist or a blocker.
• E.g: Tolazoline and Phentolamine.

6. Irreversible Alpha Blockers
• They produce slowly developing, prolonged adrenergic
blockade that is not overcome by E. They are irreversible
-blockers, because beta- haloalkylamines in the molecules
alkylate alpha- receptors .
• Mechanism of action: Nonselective covalent binding to
α1 and α2receptors. Irreversibly binds
• E.g.: Dibenamine, Phenoxybenzamine.

7. Selective Alpha one Blocker
• Definition: Alpha-1 blockers(also called alpha-adrenergic
blocking agents) constitute a variety of drugs that reduce the
effect alpha-1-adrenergic receptors.
• SAR: It consist of three components:
1. Quinazoline Ring,
2. Piperazine Ring
3. Acyl Moiety
• The 4-amino group on the quinazoline ring is very important
for 1-receptor affinity.
• Although they possess a piperazine moiety attached to the
quinazoline ring, this group can be replaced with other
heterocyclic moieties (e.g., piperidine moiety) without loss of
affinity.
• The nature of the acyl group has a significant effect on the
pharmacokinetic properties.

8. THANK
YOU…