Anti-Anginal Drugs – This book covers the entire syllabus of “Pharmacology” prescribed by BNMC- for diploma in nursing science & midwifery students. We tried to accommodate the latest information and topics. This book is an examination setup according to the teachers’ lectures and examination questions.
At the end of the book, previous questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourish. The unique way of presentation may make your reading of the book a pleasurable experience.
Anti-Anginal Drugs
Drugs used in the treatment of angina pectoris are called antianginal drugs or, coronary vasodilators.
Classification of Anti-anginal drugs:
A. Organic nitrites and nitrates:
Nitrites:
- Na+ nitrite
- Amyl-nitrite
- octyl-nitrite
Nitrates:
- Glyceryl tri-nitrate (GTN)
- Isosorbidedi-nitrate
- Isosorbide mono-nitrate
- Reduce pre-load.
- Reduce after load.
- Coronary vasodilatation
- Used for acute attack
B. Calcium channel blockers:
- Nifedipine
- Verapamil
- Diltiazem.
- Reduce contractility.
- Reduce after-load
- Coronary vasodilatation
C. B-adrenoceptor blockers:
- Atenolol
- Propranolol
- Oxaprenolol decrease myocardial contractility Decrease heart rate.
D. Xanthene group:
- Aminophylline
- Thiophylline
E. Newer drugs:
- Pre-hexilene
- Dipyridamol
Used as coronary vasodilator (prophylactic use)
Pharmacological actions of Nitro-glycerine (GTN)
1. Cardiovascular effects:
- Reduce preload (due to venodilatation)
- Reduce after-load (due to generalized vasodilatation)
So, net effect: reduce myocardial work and thus reduce myocardial 02 demand.
- Dilates coronary arteries & thereby increase coronary blood flow to ischaemic myocardium.
- Vasodilatation of intracranial vessels: (produces throbbing headache).
- Dilates retinal and orbital blood vessels thus increase intraocular pressure (top) which leads to Glaucoma.
2. Other effects:
a) Relaxation of bronchial smooth muscle.
b) Relaxation of gastrointestinal smooth muscle. So decrease GIT motility,
c) Relaxation of the smooth muscle of the biliary tract, urethra and uterus.
Therapeutic use of Nitrates
1) Angina pectoris (prophylaxis and treatment):
- Acute attack: GTN.
- Prophylaxis: Isosorbide mononitrate.
2) Congestive cardiac failure (CCF)
3) Myocardial infarction (MI).
Contra-indication of Nitrate
1) Known organic nitrate intolerance.
2) Angina due to severe anaemia.
3) High intra-cranial pressure.
4) Glaucoma.
5) Migraine.
Adverse effects of organic nitrates
| Flashing of the face | Due to dilatation of blood vessels in facial region |
| Throbbing headache | Pressing of sensory nerve due |
| Postural hypotension | Due to reduction in central venous pressure |
| Syncopal attack Reflex tachycardia. | |
| Methimoglobinaemia | due to formation or, mathemoglobin from hemoglobin |
| Nitrate tolerance |
For more curiosity:
Nitrate tolerance
During long term continuous administration, the nitrate effects are gradually lowered and finally resulting in partial or complete loss of its benefit. This phenomenon is so called nitrate tolerance and basic biochemical mechanism in it is reduced cGMP release in vascular smooth muscles. A nitrate free period of 1-2 hours every 24 hours helps to prevent development of tachyphylaxis.
Formulation of GTN
➤ Sublingual: 500 mg tab/day.
➤ Slow-release buccal tablet: 1-5 mg/6 hourly.
➤ Percutaneous as a paste: 5-10 mg/12 hourly.
Drug interactions
➤ GTN + Anti-hypertensive/major tranquillizer/Tricyclic antidepressants: Development of hypotension.
➤ GTN + Diuretics: Hypovolemia develops
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