Classification of Antihistamines

CLASSIFICATION

1. H1-Antagonists with classical structures

According to the chemical features, they are further classified as follows:

a.            Ethylene diamine derivatives

b.           Amino alkyl ether analogues

c.            Cyclic basic chain analogues

d.           Mono amino propyl analogues

e.            Tricyclic ring system or Phenothiazine derivaties

f.Dibenzocyclo heptenes

g.           Miscellaneous agents

h.           Newer agents

a. Ethylene diamine derivatives

b. Amino alkyl ethers

c. Cyclic basic chain analogues or piperazine derivatives

d. Mono amino propyl analogues

d. i. Saturated analogues

d. ii. Unsaturated analogues

e. Tricyclic ring systems or phenothiazine derivatives

f. Dibenzocyclo heptenes

g. Miscellaneous

h. Newer agents

II. H1-Antagonists with nonclassical structures

i. Azelastine

ii. Tazifylline

iii. Astemizole

III. Nonsedative H1-antihistamines

Nonsedative antihistamines bind only to peripheral H1-receptors and produce with little or no sedation because of poor CNS penetration and lower affinity for central histaminic activity.

These are divided into two main classes:

1.           Piperazine derivatives—Cetirizine

2.           Pyridine and piperidine derivatives—Loratadine, Fexofenadine, Terfenadine, Astemizole, Acrivastine

i. Loratadine

ii. Epinastine

iii. Rocastine

iv. Cetirizine

v. Fexofenadine

vi. Acrivastine

IV. Inhibition of histamine release (mast cells stabilizers)

i. Cromolyn sodium

ii. Nedocromil sodium