Which is not a 2nd generation antihistaminic ?
Cyclizine Histamine is a naturally occuring amine. It is found in most body tissues but is predominantly secreted by mast cells. Histamine acts as a local hormone (autacoid) i.e. it acts within the immediate vicinity of its release. It main physiological effects are on: Blood vessels ? - Aerioles are dilated - Capillary permeability is increased Smooth muscles -- Cause contraction of the smooth muscles G.I.T. -- Increase gastric acid secretion Histamine acts through two receptors - H1 --> mediates edema and vascular effects of Histamine - H2 --> mediates effect on gastic secretion. Hi receptor antagonists : T- hey are classified in two types (i) First generation antihistamines (ii) Second generation antihistamines The term antihistamine is unsatisfactory for the first generation or older generation antihistamine because besides blocking histamine receptors, they also show considerable blocking activity against - muscarinins receptors - serotonin receptors - a adrenergic receptors They also enter the brain readily and cause sedation. Because of their non-specificity and their highly sedative action, they have a great tendency to cause serious adverse effect. Because of these disadvantages, second generation antihistamines were developed which are more selective for H1 receptor and largely free of antimuscarinic and antiadrenergic activity. The newer second generation antihistamines penetrate the blood-brain barrier poorly and are largely devoid of sedative effects.
Loraudine
Acrivastatine
Cyclizine
None of the above