Non sedating h1 antihistamines
While cetirizine does not undergo extensive metabolism or metabolism by the cytochrome P450 enzyme, it does undergo some metabolism by other means, the metabolic pathways of which include oxidation and conjugation.
The 1-[(4-chlorophenylmethyl]-piperazine is alkylated with methyl (2-chloroethoxy)-acetate in the presence of sodium carbonate and xylene solvent to produce the Sn2 substitution product in 28% yield.
Saponification of the acetate ester is done by refluxing with potash in absolute ethanol to afford a 56% yield of the potassium salt intermediate.
This is then hydrolyzed with aqueous HCl and extracted to give an 81% yield of the carboxylic acid product.
stimulates the signaling pathways of inositol phospholipid culminating in the formation of inositol 1,4,5- triphosphate (Ins P3) and diacylglycerol (DAG), leading to an increase in intracellular calcium.
Historically, the potency of antihistamines was verified through standard pharmacological trials, particularly from guinea pig ileum or tracheal smooth muscle contraction.4 In these tissues, the drugs cause a parallel displacement in the histamine concentration/ response.
Many patients seeking help with withdrawal symptoms report having taken cetirizine for more than three years, while others report having taken it for no longer than one week. Second-generation antihistamines like cetirizine are less able to cross the blood–brain barrier and therefore have diminished effects on the central nervous system compared to first-generation drugs.As such, they are less likely to cause drowsiness or memory impairment.Cetirizine is an effective agent in treating the symptoms of Kimura's disease which predominantly affects the lymph nodes and soft tissue of the head and neck in the form of tumor-like lesions.Cetirizine's properties of being effective both in the treatment of pruritus (itching) and as an anti-inflammatory agent make it suitable for the treatment of the pruritus associated with these lesions.
Second generation antihistamines differs from first generation because of their high specificity and affinity for peripheral H -antihistamines in the treatment of allergic patients is similar, even when comparing first- and second-generation drugs, these drugs are still very different in terms of their chemical structure, pharmacology and toxic properties.