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PubMed1993

Positive- and negative-ion mass spectrometry of diphenylmethane antihistaminics and their analogues and rapid clean-up of them from biological samples.

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra are presented for 15 compounds of diphenylmethane antihistaminics and their analogues, and each fragmentation pathway was analyzed. In the PIEI mode, molecular peaks were very small or missing for most compounds. Peaks at m/z 58, due to a dimethylaminomethyl group liberated, constituted base peaks in five compounds. Peaks at m/z 165 and/or 167, due to diaromatic rings plus a methyl group, appeared in most compounds. In the PICI mode, peaks due to M+H and M+C2H5 appeared in all compounds. Peaks due to diaromatic rings plus a methyl or ethyl group constituted base peaks in five compounds, which had an ether bond in their structures. In the NICI mode, anions at m/z M-H appeared in most compounds. Peaks at m/z 35 were observed for compounds having a chlorine group in their structures. Detection limits for total ion monitoring of these compounds were 20-50 ng on column in the PIEI mode, 100-200 ng in the PICI mode and 500-1000 ng in the NICI mode. A rapid and simple clean-up procedure of these drugs with use of Sep-Pak C18 cartridges is also presented. The drugs could be detected by gas chromatography with DB-1 and DB-17 capillary columns with satisfactory separation from impurities in their underivatized forms. The recovery of the drugs, which had been added to whole blood and urine, was more than 60% except for meclizine.

Benzhydryl Compounds↗

PubMedDate not supplied

Antihistamines reverse blood-ocular barrier breakdown in experimental diabetes.

Retinal and other tissue histamine synthesis is increased in experimental diabetes; histamine infusion causes blood-ocular barrier breakdown in nondiabetic rats. We have examined the hypothesis that antihistamines prevent blood-ocular barrier breakdown in streptozotocin diabetes using male Sprague-Dawley rats held 28 days. During the last 7 days they were divided into these treatment groups: control (C), untreated diabetic (D), diabetic rats receiving diphenhydramine-HCl (B), diabetic rats receiving ranitidine (R) and diabetic rats receiving diphenhydramine and ranitidine (BR). Vitreous albumin content was measured 6 hr following fluorescein isothiocyanate bovine serum albumin (FITCBSA) injection. Data show that D had a 98.3% increase in vitreous body FITCBSA over C (p less than 0.05) while B and R showed respective decreases of 34.9% and 51.4% compared to D, R being significantly lower than D (p less than 0.05). BR showed a decrease of 71% (p less than 0.05) compared to D, and R and BR groups were not significantly different from C (p less than 0.05). Leakage into the vitreous was from the retina, not the ciliary body. These data indicate that 1) experimental diabetes results in elevated blood-ocular barrier permeability, which can be reversed by diphenhydramine-HCl and ranitidine; and 2) histamine H1- and H2-receptor activation and interaction by altered endogenous histamine metabolism may mediate blood-ocular barrier breakdown, implicating a pathogenic role of histamine in diabetic retinopathy.

Animals↗

PubMed2006

Synthesis of some substituted pyrazinopyridoindoles and 3D QSAR studies along with related compounds: piperazines, piperidines, pyrazinoisoquinolines, and diphenhydramine, and its semi-rigid analogs as antihistamines (H1).

3D QSAR studies on the title compounds led to the development of a model with three biophoric sites and six secondary sites viz. H-acceptor (ACC), H-donor (DON), heteroatom (presence), hydrophobic (hydrophobicity), steric (refractivity), and a ring (presence) along with total hydrophobicity and total refractivity as global properties. The model predicted the test set of compounds reasonably well. Three of the five newly synthesized 2-substituted octahydropyrazinopyridoindoles have shown potent antihistaminic H(1) activity with less toxicity and sedation potential.

Animals↗

PubMed2005

Synthesis and pharmacological investigation of novel 1-substituted-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones as a new class of H1-antihistaminic agents.

A series of novel 1-substituted-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones 7 were synthesized by the cyclization of 2-hydrazino-3-phenylquinazolin-4(3H)-one 6 with various one carbon donors. The starting material 2-hydrazino-3-phenylquinazolin-4(3H)-one 6, was synthesized from aniline 1 by a novel innovative route. When tested for their in vivo H(1)-antihistaminic activity on conscious guinea pigs all the test compounds protected the animals from histamine induced bronchospasm significantly, whereas the compound 1-methyl-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-one 7b (percentage protection 70.7%) was found to be equipotent with the reference standard chlorpheniramine maleate (percentage protection 71%). These compounds show negligible sedation ( approximately 5%) when compared to the reference standard (26%). Hence they could serve as prototype molecules for future development.

Animals↗

PubMed2005

Stability studies on some benzocycloheptane antihistaminic agents.

The photostability of selected benzocycloheptane antihistaminic agents, namely, loratadine (I), pizotifen (II), ketotifen fumarate (III) and cyproheptatidine (IV), was investigated. Both I and II were photolabile while III and IV were photostable. To perform stability studies on the photolabile compounds (I and II), specific stability-indicating high performance liquid chromatographic (HPLC) methods were established. The accuracy, precision and reliability of the developed HPLC methods for the assay of I and II in their pharmaceutical dosage forms were reported. Assay results for both drugs were within R.S.D. values <2%. The stability-indicating power of the developed methods was validated through study of UV-degraded solutions of I and II contained in quartz cells. The photostability of both drugs was studied under UV-irradiation at 254 nm. The photodegradation kinetics of both drugs, studied in different solvents, are also reported. TLC fractionation of photodegraded solutions of both drugs, revealed two fluorescent photodegradates of drug I. The use of UV-absorbers (ascorbic acid and p-aminobenzoic acid (PABA)) enhanced the photostability of both drugs possibly through a spectral-overlay effect.

Benzocycloheptenes↗

PubMed2004

Simultaneous analysis of the H1-antihistamine acrivastine and the decongestant pseudoephedrine hydrochloride by high-performance liquid chromatography.

High-performance liquid chromatography (HPLC) was used for the simultaneous quantification of the H(1)-antihistamine acrivastine and the decongestant pseudoephedrine hydrochloride. Both compounds were detected at the wavelength of 214 nm. The influence of the mobile phase and the detection wavelength was evaluated and optimized. This method was used to assay various samples from studies of the commercial preparation Semprex-D capsules. The method was found to be accurate, specific, selective, rapid, and versatile for use in routine quality control analyses.

Calibration↗

PubMed2006

Quantification of antihistamine acrivastine in plasma by solid-phase extraction and high-performance liquid chromatography.

An automated solid-phase extraction method was developed for the determination of the H1-antihistamine acrivastine in plasma samples. Acrivastine was analyzed at the wavelength of 254 nm using a reversed-phase HPLC assay. Both extraction procedure and analytical condition were optimized and validated for maximum recovery and resolution. The developed method was further applied to plasma samples collected from an in vivo pharmacokinetic study in rabbits. The assay was found to be simple, specific, accurate and reproducible.

Animals↗

PubMed2007

Extracts from The Cochrane Library: antihistamines and/or decongestants for otitis media with effusion (OME) in children.

The "Cochrane Corner" is a quarterly section in the Journal that highlights systematic reviews relevant to otolaryngology-head and neck surgery, with invited commentary to highlight implications for clinical decision making. This installment features a Cochrane Review entitled "Antihistamines and/or decongestants for otitis media with effusion (OME) in children," which recommends against treatment because of no demonstrable benefits but significant potential for harm.

Comment↗

PubMed2006

Utility of NBD-Cl for the spectrophotometric determination of some skeletal muscle relaxant and antihistaminic drugs.

A simple, accurate, precise and sensitive colorimetric method for the determination of some skeletal muscle relaxant drugs, namely orphenadrine citrate (I), baclofen (II), antihistaminic drugs as acrivastine (III) and fexofenadine hydrochloride (IV) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) in non-aqueous medium. The orange color products were measured at 472, 465, 475 and 469 nm for drugs I, II, III and IV, respectively. The optimization of various experimental conditions was described. Beer's Law was obeyed in the range (2.5-17.5), (5-70), (2.5-25) and (10-50)microg/ml for drugs I, II, III and IV, respectively. The molar absorptivity (epsilon), sandell sensitivity, detection((LOD)) and quantitation limits((LOQ)) are calculated. The procedure was favorably applied for determination of certain pharmaceutical dosage forms containing the studied drugs. The obtained results were compared with the official and reported methods. There were no significant differences between proposed, reported and the official methods.

4-Chloro-7-nitrobenzofurazan↗

PubMed2005

Clemastine, a conventional antihistamine, is a high potency inhibitor of the HERG K+ channel.

Human ether-à-go-go-related gene (HERG) encodes the alpha-subunit of channels carrying the cardiac rapid delayed K+ current (Ikr), which is a major determinant of the duration of ventricular action potentials (APs) and of the QT interval. This study investigated the effects on HERG channel current (IHERG) of clemastine, a "conventional" antihistamine that has been associated with delayed ventricular repolarization in vitro, but for which no adverse effects on the human QT interval have been reported. Whole-cell patch-clamp measurements of IHERG were made at 37 degrees C from human embryonic kidney (HEK 293) cells stably expressing HERG channels. IHERG tails at -40 mV following depolarizing pulses to +20 mV were inhibited by clemastine with an IC50 value of 12 nM; this drug concentration also produced a marked inhibition of peak IHERG elicited during an AP voltage-clamp command. Clemastine produced a reversible approximately -5 mV shift in the IHERG steady-state voltage-dependent activation curve, but voltage-dependence of inactivation was unaffected. Development of IHERG inhibition by clemastine showed strong time-dependence. The S6 point mutations Y652A and F656A greatly attenuated the inhibitory effect of clemastine. We conclude that clemastine is a high potency inhibitor of IHERG, that this action is contingent upon channel gating and that clemastine interacts with a high affinity drug-binding site in the HERG channel pore cavity. The disparity between clemastine's potent IHERG inhibition and a lack of QT-prolongation in normal clinical use underscores the need to interpret HERG IC50 data for novel compounds in the context of information from other safety assays.

Animals↗

PubMed1998

Causal prophylactic activity of antihistaminic agents against Plasmodium yoelii nigeriensis infection in Swiss mice.

The causal prophylactic activity of five tricyclic anti-histaminic agents (histamine H1-receptor antagonists) cyproheptadine, ketotifen, loratadine, azatadine and terfenadine was evaluated in an experimental murine malaria model. Sporozoite induced infections with Plasmodium yoelii nigeriensis (N-67), a strain innately resistant to choloroquine, were employed for the efficacy test and pyrimethamine and primaquine were used as standard reference drugs. Treatment with cyproheptadine or ketotifen at 5 mg/kg and terfenadine at 50 mg/kg, orally for 3 days (-1, 0, +1) completely prevented the establishment of patent infection in mice inoculated with 1 x 10(5) sporozoites on day 0. Partial activity was recorded with lower doses of the above agents as well as with azatadine and loratadine at 10 mg/kg as indicated by marginal delay in the development of patent infection after sporozoite challenge. None of these agents showed blood schizontocidal activity at doses found effective in the causal prophylactic test, though initial suppression of parasitaemia was observed with cyproheptadine and ketotifen at higher doses. This study is the first report on efficacy of antihistaminic agents for growth inhibition of pre-erythrocytic stages of any malaria parasite.

Animals↗

PubMed1980

Effects of topically applied occular decongestant and antihistamine.

In two independent studies including 25 subjects each, naphazoline caused significant whitening (but did not prevent itching) in the histamine-induced red, itchy eye. Antazoline inhibited itching (but not redness) to a significant degree in the same model. The combination of naphazoline and antazoline produced significant whitening and inhibition of itching in all eyes challenged by histamine. The combination of the two drugs was more effective than either component alone in preventing redness. The antihistamine and combination of antihistamine/vasoconstrictor were equally effective in arresting itching.

Antazoline↗

PubMed1999

In vitro inhibition of human liver drug metabolizing enzymes by second generation antihistamines.

Cetirizine, terfenadine, loratadine, astemizole and mizolastine were compared for their ability to inhibit marker activities for CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A4 and for some glucuronidation isoenzymes in human liver microsomes. The most pronounced effects were observed with terfenadine, astemizole and loratadine which inhibited CYP3A4-mediated testosterone 6beta-hydroxylation (IC50 of 23, 21 and 32 microM, respectively) and CYP2D6-mediated dextromethorphan O-demethylation (IC50 of 18, 36 and 15 microM, respectively). In addition, loratadine markedly inhibited the CYP2C19 marker activity, (S)-mephenytoin 4-hydroxylation (Ki of 0.17 microM). Furthermore, loratadine activated the CYP2C9-catalyzed tolbutamide hydroxylation (ca. 3-fold increase at 30 microM) and inhibited some glucuronidation enzymes. Mizolastine appeared to be a relatively weak and unspecific inhibitor of CYP2E1, CYP2C9, CYP2D6 and CYP3A4 (IC50Ss in the 100 micromolar range). Cetirizine demonstrated no effect on the investigated activities. A comparison of the inhibitory potencies of cetirizine, terfenadine, loratidine, astemizole and mizolastine with their corresponding plasma concentrations in humans suggests that these antihistamines are not likely to interfere with the metabolic clearance of coadministered drugs, with the exception of loratidine, which appears to inhibit CYP2C19 with sufficient potency to warrant additional investigation.

Astemizole↗

PubMed2002

ReN 1869, a novel tricyclic antihistamine, is active against neurogenic pain and inflammation.

The tricyclic compound (R)-1-(3-(10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ylidene)-1-propyl)-3-piperidine carboxylic acid (ReN 1869) is a novel, selective histamine H(1) receptor antagonist. It is orally available, well tolerated, easily enters the central nervous system (CNS) but no adverse effects are seen in mice at 300 mg/kg. ReN 1869 at 0.01-10 mg/kg is antinociceptive in tests of chemical nociception in rodents (formalin, capsaicin, phenyl quinone writhing) but not in thermal tests (hot plate and tail flick). ReN 1869 amplifies the analgesic action of morphine but does not show tolerance after chronic dosing. Moreover, the compound is effective against inflammation of neurogenic origin (antidromic nerve stimulation, histamine-evoked edema) but not in carrageenan-induced inflammation. We suggest that ReN 1869, via H(1) blockade, counteracts the effect of histamine liberated from activated mast cells and inhibits pain transmission in the dorsal spinal cord. ReN 1869 represents a new class of antihistamines with pain-relieving properties that probably is mediated centrally through histamine H(1) receptors but alternative mechanisms of action cannot be excluded.

Animals↗

PubMed2002

Titrimetric and spectrophotometric assay of some antihistamines through the determination of the chloride of their hydrochlorides.

Two simple, rapid and reliable methods for the determination of four antihistamines based on the measurement of the chloride of their hydrochlorides are described. In the titrimetric method, the chloride content of each drug is determined by titrating with mercury(II) nitrate using diphenylcarbazone-bromothymol blue as indicator. In the spectrophotometric method, to a fixed concentration of mercury(II)-diphenylcarbazone complex different amounts of drug are added and the decrease in absorbance of mercury(II)-diphenylcarbazone complex, consequent to the replacement of diphenylcarbazone of the complex by the chloride of the drug, was measured at 540 nm. The stoichiometry of the reaction that forms the basis for titrimetry is assessed. Different variables affecting the color formation in spectrophotometry were studied and optimized. At the wavelength of maximum absorption, Beer's law is obeyed in the 0-100 microg ml(-1) range. The molar absorptivity and Sandell sensitivity are calculated. The proposed methods were applied for the analysis of pharmaceutical formulations containing these drugs. Statistical treatment of the experimental results indicates that the procedures are precise and accurate. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedures as shown by the recovery studies.

Cetirizine↗

PubMed1975

Antihistamine blockade of the ovarian hyperstimulation syndrome. II. Possible role of antigen-antibody complexes in the pathogenesis of the syndrome.

Antihistamine can prevent the ovarian hyperstimulation syndrome in the rabbit. The mechanism underlying this experimental observation has not been elucidated. Our experiments were directed at the question of whether antigen-antibody complexes are a factor in the development of the ovarian hyperstimulation syndrome. The results do not support the theory that antigen-antibody complexes play a role in the pathogenesis of this syndrome.

Animals↗

PubMed2003

Application of thin-layer chromatographic data in quantitative structure-activity relationship assay of thiazole and benzothiazole derivatives with H1-antihistamine activity. II.

Quantitative structure-activity relationship (QSAR) analysis of H1-antihistamine activity was carried out and chromatographic data of 2-[2-(phenylamino)thiazol-4-yl]ethanamine, 2-(2-benzyl-4-thiazolyl)ethanamine, 2-(2-benzhydrylthiazol-4-yl)ethylamine derivative, and 2-(1-piperazinyl- and 2-(hexahydro-1H-1,4-diazepin-1-yl)benzothiazole derivatives were obtained. Normal-phase (NP) TLC plates (silica gel 60F254), impregnated with solutions of selected amino acid mixtures (L-Asp, L-Asn, L-Thr and L-Lys) were used in two developing solvents as human histamine H1-receptor (hH1R) antagonistic interaction models. The lipophilicity data of the examined compounds were obtained and used in the QSAR assay. Using regression analysis, relationships between chromatographic and biological activity data were found. The correlations obtained in the present experiment with NP-TLC are more significant that those obtained in the experiment with RP2 TLC, because of the optimal fitting of the chromatographic system conditions to the lipophilicity of solutes. All proposed chromatographic models should facilitate pre-selection of the new drug candidates. The correlations of calculated pA2(H1) values of the tested compounds predicted by the use of the best equations versus their pA2(H1) obtained from the biological tests were significant (R2 = 0.91-0.94).

Benzothiazoles↗

PubMed1997

Is an antihistamine-decongestant combination effective in temporarily relieving symptoms of the common cold in preschool children?

OBJECTIVE: To determine whether an antihistamine-decongestant combination (ADC) is superior to placebo in temporarily relieving symptoms of upper respiratory tract infection (URI) in preschool children. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Four pediatric offices in the Seattle, Wash, area. PARTICIPANTS: Children 6 months through 5 years of age with a URI of less than 7 days' duration. METHODS: Children were randomly assigned to receive an ADC (brompheniramine maleate-phenylpropanolamine hydrochloride) or placebo as needed for URI symptoms. Two hours after each dose of study medication, changes in the child's runny nose, nasal congestion, cough, and sleep status were assessed by means of a standardized questionnaire. RESULTS: A total of 175 responses were recorded for 59 patients. There were no statistically significant differences in symptom improvement between the ADC and the placebo group (runny nose, p = 0.48; nasal congestion, p = 0.94; cough, p = 0.66). However, the proportion of children asleep 2 hours after receiving the ADC was significantly higher than the proportion receiving placebo (46.6% vs 26.5%; p = 0.01). Results were unchanged after control for the correlated nature of repeated responses, age, symptom duration, use of acetaminophen, time that the medication was given, and parental desire for medication. CONCLUSIONS: The ADC was equivalent to placebo in providing temporary relief of URI symptoms in preschool children. However, the ADC did have significantly greater sedative effects than did placebo.

Brompheniramine↗