Antihistamines properties

When the additional nitrogen atom is included in one of the aromatic rings, on the other hand, there is obtained a compound with antihistaminic properties. Reaction of the Grignard reagent from 4-chlorobromobenzene with pyridine-2-aldehyde gives the benzhydrol analog (12). The alcohol is then converted to its sodium salt by means of sodium, and this salt is alkylated with W-C2-chloroethyl)dimethylamine. Carbinoxamine (13) is thus obtained. ... 

FIGURE 9.20 Design of multiple ligancl activity, (a) Dual histamine HI receptor and leukotriene receptor antagonist incorporating known antihistaminic properties of cyproheptadine and LTD4. (b) Joint ACE/NEP inhibitor formed from incorporating similarities in substrate structures for both enzymes. From [57],... 

Antihistaminic properties are well known to be preserved even when nitrogen is included in a ring, such as in clemastine (36). Synthesis of 36 is begun by reaction of 4-chlorobenzophenone (33) with... 

Pharmacoiogy Cyclizine and meclizine have antiemetic, anticholinergic, and antihistaminic properties. 

Equally effective as other tricyclic antidepressants for depression distinguishing characteristics include sedative, anxiolytic, antihistaminic properties... 

Trazodone shows significant blockade of peripheral a-adrenergic receptors and moderate antihistamine properties that may account for priapism and somnolence, respectively. Trazodone is almost entirely devoid of anticholinergic activity (Cusack et al., 1994). 

Imipramine also came from a class of substances having antihistaminic properties, and was earmarked and tested clinically as a possible competitor... 

The tranquillizers like benzodiazepines (diazepam 5-10 mg oral, or lorazepam 2 to 4 mg IM, IV are now preferred for preanaesthetic medication because they produce tranquillity, have better muscle relaxant property and smoothen induction. Other tranquillizer compounds include phenothiazines which possess sedative, antiemetic and antihistaminic properties. They can be given orally as well as parenterally. 

The monocyclic thiepins are less stable than the corresponding oxepins and the few known examples have to date no significant commercial applications. Several members of the much more stable dibenzo[6,/]thiepin series have however been synthesized and tested for biological activity. Thus thiepins (259) and (260) were found to have antiinflammatory and antihistamine properties respectively (74JHC17). 

Amoxapine and maprotiline share most drug interactions common to the TCA group. Both are CYP2D6 substrates and should be used with caution in combination with inhibitors such as fluoxetine. Amoxapine and maprotiline also both have anticholinergic and antihistaminic properties that may be additive with drugs that share a similar profile. 

The introduction of two para-substituents reduce strongly the antihistamine properties, indicating that the two phenyl nuclei have different functions in binding to the receptor. This observation is confirmed by the large difference in activity between the enantiomers of 4, 41-CH3-diphenhydramine. 

Elegant experiments conducted by the group of Schwartz in Paris [15] identified a clear relationship between the level of occupation of H, receptor in the CNS and sleep induction. When Nicholson et al. [16] showed that, for two pairs of enantiomers of chiral antihistamine, only the active (antihistaminic) enantiomer caused sleep in man, it became clear that the antihistaminic properties are responsible for drowsiness. 

The potentiation of sedative effects from benzodiazepines when combined with centrally acting drugs with antihistamine properties (for example first-generation antihistamines, tricyclic antidepressants, and neuroleptic drugs) can pose problems (143). Antihistamines that do not have central actions do not interact with benzodiazepines as in the case of mizolastine and lorazepam (144), ebastine and diazepam (145), and terfenadine and diazepam (143). 

Sedative effects and weight gain may be due to antihistamine properties... 

Citalopram s unique mild antihistamine properties may contribute to sedation and fatigue in some patients... 

May be effective in treating skin conditions because of its strong antihistamine properties... 

An example of a drug separated by preparative HPLC is cetirizine dihydrochloride, a racemic drug that is a second generation antihistamine Hi receptor antagonist. Studies on the effect of racemic and R (25) and S-Cetirizine (26) on nasal resistance indicated that both racemic and the R-enantiomer had similar activity. The racemate and R-enantiomer inhibit histamine and induced an increase in nasal resistance, thus indicating the antihistaminic properties of R-Cetirizine (45). TheiS-enantio-... 

Lowe E, MacMillan R, Katser M. The antihistamine properties of Benadryl, beta-dimethyl-aminoethyl benzhydryl ether hydrochloride. J Pharmacol Exp Ther 1946 86 229. 

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