β-adrenoceptor blockers

Most β-adrenoceptor blockers are reversible and competitive antagonists for β-receptors. β-adrenoceptor blockers are of two types:

Beneficial effects in angina:
1. Through its β-blocking effect, it decreases sympathetic activation (i.e. catecholamine induction) of heart, resulting in

These effects decrease oxygen requirement of the muscles of the heart at rest as well as during physical activity.
2. Reduced heart rate causes an elevated diastolic perfusion time that promotes myocardial perfusion.

Adverse effects in angina:
As the heart rate is decreased, it causes an increased end diastolic volume and promoted ejection time.
This results in increased myocardial oxygen requirement.

Uses of β-blockers:
1. They are useful in classic angina

2. They decrease blood pressure in hypertension
3. They are helpful in cardiac arrhythmias
4. They are helpful in glaucoma
5. They are also helpful in therapy of myocardial infarction
6. Prophylactically helpful for treating migraine headache
It is used synchronously with nitrates to lessen its unwanted effects. On the other hand, this combination is also helpful for promoting duration of exercise as well as tolerance.

Contraindications:
It is contraindicated in patients of:
1. Asthma
2. Peripheral vascular disease
3. Chronic obstructive pulmonary disease
4. Diabetes