Question

An antihistamine is a drug that inhibits the physiological effects of histamine. Their mechanism of action involves the competitive inhibition of histamine receptors.

a. Define what is meant by a competitive antagonist.

b. Discuss the physiological effects of antihistamines. Consider the anticholinergic and sedative effects as well as the effects on skin and the cardiovascular system.

c. Explain the advantage of using peripherally acting antihistamines.

Answer 1

A)

Competative antagonist.

A Competative antagonist binds at agonist site and block the agonists action of binding receptor and activating the receptor to produce a biological response. Simply we can conclude that agonists bind receptor to produce biologic response but antagonists are opposite for that. It means antagonists block this site's.

B)

Psychological effects of antihistamines:-

Their are many effects made by brain directly and indirectly. The effects made by brain due to antihistamined includes:-

* Daytime sleepiness.

* Decreasing the sleep quality.

* Reduce sleep latency.

* Drowsiness.

* Fatigue.

* Sedation.

* Dream anxiety, etc.

Anticholinergic and sedative effects:-

The effects includes:-

Sedative effects:-

* Drowsiness.

* Headache.

* Sickness.

* Amnesia.

* Low blood pressure.

Effects of anticholinergic:-

* Increased heart rate.

* Decrease in sweat.

* Dry mouth.

* Urinary retention.

* Blurred vision.

* Constipation,etc.

anticholinergic effects on skin:-

* Dry skin.

* Tachycardia.

* Dilated pupils, etc.

anticholinergic effect on cardiovascular:-

* Myocardial infarction.

* Stroke,etc.

C)

The 2 most important advantages of using peripherally acting antihistamines are:-

* They are non-sedative.

* They are most effective and once-a-day dose increases compliance.