Drugs act on sympathetic nervous system: Alpha & Beta blocker, Centrally acting drug

Today post focuses on drugs that alter sympathetic nervous system. They are

(i)  Adrenoceptor blockers- a-blockers, b-blockers

(ii) Centrally acting drugs

To understand the mechanism of adrenoreceptor blockers, let us revise on the functions of different receptors.

1. How do alpha blockers work and how to relate them to their side effects?
 Activation of alpha 1 leads to vasoconstriction-> increase the blood pressure (BP).
Blocking alpha-1 prevent vasoconstriction -> decrease in BP (alpha-1 selective).
therefore, the main side effects include first dose phenomenon and orthostatic hypotension (postural hypotension).

 Activation of alfa-2 :inhibits the release of noradrenaline (NA)->decrease heart rate and contractility.
the non-selective alpha blocker blocks alfa-2->  increase heart rate and contractility.
Side effect: decrease BP (from blocked alpha-1) + increase HR (from blocked alpha-2) = reflex tachycardia.

2.How do beta blockers work?
Non-selective beta blocker block both beta-1&2.
Blocking beta-1 (in heart)->decrease heart contractile force and HR->side effect:bradycardia.
Blocking beta-2 ->inhibit the relaxation bronchus muscles->contraindicated in patient (pt) with COPD/asthma.
                          ->also inhibit vasodilation->peripheral vasoconstriction.

Summary

alpha blockers

• Type

this is a screenshot from Dr.Mai Chung Wai's notes on Drug Design Based On Protein Structure, covered in Sem 4 Biotechnology.

• Use

-can be used with other antihypertensive drugs in the treatment of resistant hypertension.

Beta blocker

• Type

beta 1 selective: Practolol, Atenolol, Metoprolol (P.A.M)

non-selective: propranolol,pindolol,timolol

• Uses 

1. Management of stable angina & acute coronary syndromes

2. Hypertension treatment

3.reduce recurrence rate of myocardial infarction.

4.Management of arrhythmias

5.Heart failure treatment

• Development:

The following diagrams are the screenshoots from Dr.Mai Chung Wai's notes on Drug Design Based On Protein Structure, covered in Sem 4 Biotechnology.

                            

The development of beta blockers.

                                  

Structure of propanolol. It is good to memorise these properties for examination purpose.

for selective beta1 blocker, para-substitution is essential.

The table below summaries the properties of alpha and beta blockers.

                                             Table 1: summary of alpha and beta blockers.

Beta 1 selective blockers are useful in pt with impaired pulmonary functions and diabetics pt.

Centrally acting drugs

Table 2: centrally acting drugs

oopsss hope my handwriting is understandable.

To remember the name of centrally acting drugs, you can try to think of MCM.

a brand endorsed by EXO (based on google, not sure about 2016 tho)