Small occasional doses of azatadine are probably acceptable during breastfeeding. Larger doses or more prolonged use may cause drowsiness and other effects in the infant or decrease the milk supply, particularly in combination with a sympathomimetic such as pseudoephedrine or before lactation is well established. The nonsedating antihistamines are preferred alternatives.

A sensitive method using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS) was developed and validated for the analysis of antihistamine drug azatadine in human plasma. Loratadine was used as internal standard (IS). Analytes were extracted from human plasma by liquid/liquid extraction using ethyl acetate. The organic phase was reduced to dryness under a stream of nitrogen at 30 °C and the residue was reconstituted with the mobile phase. 5 μL of the resulting solution was injected onto the LC-MS/MS system. A 4.6 mm × 150 mm, I.D. 5 μm, Agilent TC-C(18) column was used to perform the chromatographic analysis. The mobile phase consisted of ammonium formate buffer 0.010 M (adjusted to pH 4.3 with 1M formic acid)/acetonitrile (20:80, v/v) The chromatographic run time was 5 min per injection and flow rate was 0.6 mL/min. The retention time was 2.4 and 4.4 min for azatadine and IS, respectively. The tandem mass spectrometric detection mode was achieved with electrospray ionization (ESI) iron source and the multiple reaction monitoring (MRM) (291.3 → 248.2m/z for azatadine, 383.3 → 337.3m/z for IS) was operated in positive ion modes. The low limit of quantitation (LLOQ) was 0.05 ng/mL. The intra-day and inter-day precision of the quality control (QC) samples was 8.93-11.57% relative standard deviation (RSD). The inter-day accuracy of the QC samples was 96.83-105.07% of the nominal values.

Due to the difficulty of monitoring trace levels of cyproheptadine (CYP) residues in complicated biological matrices, specific adsorption materials for the preconcentration and clean-up of CYP are indispensable. In this work, CYP was extracted from urine using dummy molecularly imprinted SPE (DMISPE) to avoid leakage of the imprinting molecules during the desorption phase. For synthesis of DMISPE, azatadine (AZA) was employed as the dummy template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2'-azobis(2-methylpropionitrile) (AIBN) as the initiator, and dichloromethane as the porogen solvent. An LC-MS/MS method was used to analyze CYP. Two MRM (multiple reaction monitoring) transitions for each analyte were monitored using diphenylpyraline hydrochloride (DPP.HCl), which was used as an internal standard. The advantages of DMISPE include obtaining less complex chromatograms and reducing ion suppression in ESI. The process efficiencies for DMISPE and SPE were 80% and 12%, respectively. In addition, the demonstrated reusability of the DMISPE cartridges is an advantage compared with single-use SPE cartridges or immunoaffinity materials.

The use of custom-made polymeric materials with high selectivities as target molecules in solid-phase extraction (SPE), known as molecularly imprinted solid-phase extraction (MISPE), is becoming an increasingly important sample preparation technique. However, the potential risk of leakage of the imprinting molecules during the desorption phase has limited application. The use of a mimicking template, called a dummy molecular imprinting polymer (DMIP), that bears the structure of a related molecule and acts as a putative imprinting molecule may provide a useful solution to this problem. In the current study, cyproheptadine (CPH) and azatadine (AZA) were used as templates in the development of an MIP and DMIP for acrylic acid and methacrylic acid monomers. Our results indicate that DMIPs have equal recognition of CPH, avoiding the problem of leakage of original template during the desorption phase relative to MIPs synthesized in presence of the print molecule CPH. Examination of the surface structure of the two polymer products by SEM shows appreciable differences in structural morphology and function of the monomers employed. These results are well supplemented by data obtained for swelling ratios and solvent uptake. Molecular modelling of CPH and AZA suggests that both substrates are similar in shape and volume.

Vestibular neuronitis was described in 1949 and 1952 by Dix and Hallpike. Two groups of patients were described, those with sudden seizures and sensations of blackout (since identified as having vestibular neuritis) and a second group with symptoms of disequilibrium and feelings of top-heaviness or imbalance. The pathology was believed to be central to the inner ear. Arslan labeled these groups as having nucleoreticular vestibular syndrome. Using a suprathreshold stapedial reflex test, Bosatra localized the pathophysiology in the brainstem, an area rich in serotonergic neurons. This author has used antiserotonergic drugs, with success, in treating patients having the symptoms identified by Dix and Hallpike in their second group (which now should be labeled nucleoreticular vestibular syndrome), properly identified as a brainstem affliction. This study describes the characteristics of this disorder, the methods of diagnosis and treatment, and the outcomes in two groups of patients studied. The study concluded that antiserotonin drugs, specifically affecting 5-hydroxytryptamine2, should be considered in the management of nucleoreticular vestibular syndrome.

Data from in vitro, in vivo, and ex vivo studies suggest that second-generation antihistamines have a number of antiallergic, anti-inflammatory properties that appear to be independent of their H1-blockade activity. First-generation antihistamines also have antiallergic, anti-inflammatory properties, as suggested by the studies with azatadine, chlorpheniramine, mepyramine, and promethazine; most other first-generation antihistamines have not been studied for these properties. In vitro studies have shown that H1-antihistamines reduce the release of proinflammatory mediators from mast cells and basophils, the chemotaxis and activation of inflammatory cells (especially eosinophils), and the expression of adhesion molecules induced by immunological and nonimmunological stimuli in epithelial cell lines. Nasal allergen challenge models have similarly demonstrated that H1-antihistamines inhibit mediator release from mast cells and basophils, and that they decrease inflammatory cell infiltration and the expression of adhesion molecules on epithelial cells. The results of published studies of the effects of H1-antihistamines on nasal allergic inflammation in humans have been summarized in this chapter. Recent investigations indicate that H1-antihistamines may modulate airway inflammation by downregulating the activity of airway epithelial cells, which have an important role in allergic airway inflammation. The modulation of adhesion molecules and of inflammatory cell infiltration by H1-antihistamines may be beneficial during long-term treatment in patients with allergic rhinitis. The rationale for this hypothesis is the persistence of inflammation on the nasal epithelial cells even when patients are symptom-free (16). All of the events affected by H1-antihistamines are important in the allergic inflammation cascade. The underlying mechanisms for such effects remain unclear, but are unrelated to H1-antagonist activity. Several studies have demonstrated that H1-antihistamines can form an ionic association with cell membranes and inhibit calcium ion influx into the mast cell or basophil plasma membrane, or inhibit Ca2+ release within the cells, and may therefore influence the signal transduction pathways. However, these effects appear to occur at concentrations higher than those achieved in therapeutic practice (126-128). It has recently been hypothesized that the anti-inflammatory activity of H1-antihistamines may be a consequence of their ability to influence the activation of genes responsible for the expression and synthesis of proinflammatory mediators (129). The contribution of the antiallergic effects of H1-receptor antagonists to their clinical efficacy is not fully understood. There have been no data suggesting that H1-antihistamines with well-documented antiallergic properties are superior to the others for which such properties have not been as extensively investigated. Additional studies are needed to elucidate the mechanisms(s) by which H1-antihistamines exert anti-inflammatory effects. This knowledge might lead to the development of novel therapies with more potent and specific anti-inflammatory effects.

A reversed-phase liquid chromatographic procedure with a micellar mobile phase of sodium dodecyl sulfate (SDS), containing a small amount of pentanol, was developed for the control of 7 antihistamines of diverse action in pharmaceutical preparations (tablets, capsules, powders, solutions, and syrups): azatadine, carbinoxamine, cyclizine, cyproheptadine, diphenhydramine, doxylamine, and tripelennamine. The retention times of the drugs were <9 min with a mobile phase of 0.15M SDS-6% (v/v) pentanol. The recoveries with respect to the declared compositions were in the range of 93-110%, and the intra- and interday repeatabilities and interday reproducibility were <1.2%. The results were similar to those obtained with a conventional 60 + 40 (v/v) methanol-water mixture, with the advantage of reduced toxicity, flammability, environmental impact, and cost of the micellar-pentanol solutions. The lower risk of evaporation of the organic solvent dissolved in the micellar solutions also increased the stability of the mobile phase.

The chromatographic behaviour of binary and ternary mixtures of several phenethylamines (phenylephrine, phenylpropanolamine, ephedrine, pseudoephedrine and methoxyphenamine) and antihistamines (pheniramine, carbinoxamine, doxylamine, chlorpheniramine, dexchlorpheniramine, dexbrompheniramine, diphenhydramine, tripolidine, azatadine and phenyltoloxamine), found in cough-cold pharmaceutical preparations, was studied using C8, C18 and cyano columns, micellar mobile phases of sodium dodecyl sulfate (SDS) and pentanol and UV detection. Using a C8 column and mobile phases of 0.05 mol l-1 SDS-6% v/v pentanol or 0.15 mol l-1 SDS-2% v/v pentanol at pH 7, more than 30 different phenethylamine-antihistamine combinations can be resolved in < 15 min. Intra- and inter-day repeatabilities and reproducibilities evaluated at three different drug concentrations (0.5, 5 and 25 micrograms ml-1, n = 10) were below 1.6, 2.5 and 2.4%, respectively. The drug amounts found in 18 formulations agreed with those declared by the manufacturers within the tolerance limits, and with those obtained using a mobile phase of 55% v/v methanol at pH 7. No interference was observed from other accompanying drugs such as acetylsalicylic acid, ascorbic acid, betamethasone, bromhexine, caffeine, codeine, dextromethorphan, paracetamol, prednisolone, salicylamide and tartrazine. The proposed procedure has the advantage over the conventional aqueous-organic procedure of using a small amount of organic solvent, which is highly retained in the SDS solution. The efficiencies are also greater. On the other hand, in the micellar system, the retentions of phenethylamines and antihistamines are similar, although the compounds can be easily resolved. In contrast, using the methanol-water mobile phase, the phenethylamines are weakly retained, whereas the antihistamines usually show a high retention.

The primary mechanism of antihistamine action in the treatment of allergic diseases is believed to be competitive antagonism of histamine binding to cellular receptors (specifically, the H1-receptors), which are present on nerve endings, smooth muscles, and glandular cells. This notion is supported by the fact that structurally unrelated drugs antagonize the H1-receptor and provide clinical benefit. However, H1-receptor antagonism may not be their sole mechanism of action in treating allergic rhinitis. On the basis of in vitro and animal experiments, drugs classified as H1-receptor antagonists have long been recognized to have additional pharmacological properties. Most first-generation H1-antihistamines have anticholinergic, sedative, local anaesthetic, and anti-5-HT effects, which might favourably affect the symptoms of the allergic response but also contribute to side-effects. These additional properties are not uniformly distributed among drugs classified as H1-receptor antagonists. Azatadine, for example, inhibits in vitro IgE-mediated histamine and leukotriene (LT) release from mast cells and basophils. In human challenge models, terfenadine, azatadine, and loratadine reduce IgE-mediated histamine release. Cetirizine reduces eosinophilic infiltration at the site of antigen challenge in the skin, but not the nose. In a nasal antigen challenge model, cetirizine pretreatment did not affect the levels of histamine and prostaglandin D2 recovered in postchallenge lavages, whereas the levels of albumin, N-tosyl-L-arginine methyl ester (TAME) esterase activity, and LTs were reduced. Terfenadine, cetirizine, and loratadine blocked allergen-induced hyperresponsiveness to methacholine. In view of the complexity of the pathophysiology of allergy, a number of H1 antagonists with additional properties are currently under development for allergic diseases. Mizolastine, a new H1-receptor antagonist, has been shown to have additional actions that should help reduce the allergic response. In animal models, mizolastine inhibits antigen-induced eosinophil infiltration into mouse skin and into the nasal cavity of guinea-pigs. Mizolastine also significantly inhibits antigen-induced neutrophil infiltration into the bronchoalveolar lavage fluids of guinea-pigs. In addition, it inhibits arachidonic acid-induced paw oedema in rats without affecting carrageenin-induced rat paw oedema, suggesting an effect on LT generation. In man, mizolastine inhibits early and late antigen-induced soluble intercellular adhesion molecule 1 (ICAM-1) levels in skin blisters. It also inhibits anaphylactic release of histamine from rodent mast cells, LTC4 and LTB4 release from mouse bone-marrow-derived mast cells, LTC4 release from rat intestinal mast cells, and 5-lipoxygenase activity of polymorphonuclear neutrophils of guinea-pig intestines and rat basophilic leukaemia cells. It is clear that a number of H1-antihistamines have multiple effects on the allergic inflammatory response. It is equally clear that these antiallergic effects are not uniformly shared among all drugs of this class. The assessment of the clinical significance of these results and research regarding the parts of the molecules responsible for these activities are underway.