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PubMed1998

Oral and topical antihistamines: pharmacologic properties and therapeutic potential in ocular allergic disease.

BACKGROUND: Allergic eye disease is a common clinical occurrence in individuals who experience local and systemic hypersensitivity reactions. The majority of ocular symptoms involve the conjunctiva and lids, which are exposed to the environment and thereby are sites of interaction between allergens and immunocompetent cells. Signs and symptoms of ocular involvement can manifest as itching, chemosis, tearing, swollen lids, and photophobia. METHODS: Histamine is a key preformed mediator released when allergen molecules crosslink to antigen-binding components of adjacent IgE molecules on mast cells or basophil surface. On its release, histamine acts on H1-receptors on a variety of tissues and cells, including blood vessels, smooth muscle, and sensory nerves. RESULTS: Drugs classified as H1-receptor antagonists, commonly referred to as the antihistamines, are among the most efficacious and frequently used medications for ocular and systemic allergy symptoms. CONCLUSION: This review focuses on the pharmacologic actions and side effects of oral first-generation sedating or classic H1-receptor antagonists; the second-generation, relatively nonsedating H1-receptor antagonists; and the topical ocular antihistamine/decongestants and single-entity antihistamine formulations.

Administration, Oral↗

PubMed1963

THE EFFECT OF SOME NEW ANTIHISTAMINES ON THE ANAPHYLACTIC MICROSHOCK OF THE GUINEA-PIG.

The dose/response curves for the protective effects of the new antihistamine compounds trimeprazine, 10-(3-diethylamino-2-methylpropyl)phenothiazine 1,1-dioxide hydrochloride (oxomemazine hydrochloride), cyproheptadine, homochlorcyclizine and methotrimeprazine against the anaphylactic microshock of the guinea-pig were similar to that of promethazine. The first three compounds, however, protected at lower doses than promethazine (5 to 10 mug/kg). The protective effect of cyproheptadine lasted longer than 24 hr.

Anaphylaxis↗

PubMed1963

AN ANTIHISTAMINE-LIKE SUBSTANCE (OR SUBSTANCES) IN EXTRACTS PREPARED FROM HUMAN TISSUES.

A method for the extraction of an antihistamine-like substance (or substances) from human tissues is described. The method has demonstrated the presence of this active principle(s) in a large variety of human tissues, so far without exception. The substance(s) has a wide range of activity in antagonizing the in vitro effects of histamine, 5-hydroxytryptamine and bradykinin and the Schultz-Dale reaction on the guinea-pig ileum and rat uterus preparations.

Anaphylaxis↗

PubMed1989

[Antimycobacterial antihistaminics].

The testing of antihistaminic compounds of various chemical classes for antimycobacterial properties is described. A lot of these compounds inhibit the growth of mycobacteria at a concentration of 8-32 micrograms/ml.

Histamine Antagonists↗

PubMed1989

Separation of some antihistamines on impregnated TLC silica plates.

Different metal salts have been tried as impregnating reagents for developing TLC separation schemes for some antihistamines on silica gel 'G' plates, using a new solvent system benzene + dimethyl formamide + acetic acid (30:10:7). Spots were visualized by spraying with a solution of Dragendroff's reagent.

Chromatography, Thin Layer↗

PubMed1998

Application of heparin to chiral separations of antihistamines by capillary electrophoresis.

A study of the chiral separations of antihistamines, including pheniramine, chlorpheniramine, brompheniramine, carbinoxamine and doxylamine in capillary electrophoresis (CE) was accomplished using heparin as a chiral additive (CA) and phosphate buffer as the background electrolyte. Several factors were shown to affect both the selectivity and the migration time, including concentration of heparin, concentration of buffer, and the pH. A dual mechanism involving both inclusion complexation and ionic interactions with heparin is thought to be responsible for the chiral recognition. In the pH range of 2.6-3.5 and reversed polarity, baseline resolutions were obtained using a wide range of buffer and heparin concentrations. Typically, chiral resolution was obtained within 50 min.

Brompheniramine↗

PubMed1981

The effectiveness of antihistamines in the common cold.

A randomized, double-blind, placebo-controlled study was done on 106 volunteers to assess the effectiveness of chlorpheniramine maleate against the common cold. The results suggest that this antihistamine is significantly effective in relieving the symptoms of a cold if used four times daily for one week, and that relief was gained with no significant increase in side effects.

Adult↗

PubMed1992

Central nervous system effects of meclizine and dimenhydrinate: evidence of acute tolerance to antihistamines.

Relative daytime drowsiness and performance impairment produced by meclizine and dimenhydrinate was assessed in 24 healthy male volunteers. Subjects received either dimenhydrinate, 100 mg, at 8:00 AM, 12:00 PM, and 4:00 PM; meclizine, 50 mg, at 8:00 AM, with placebo at 12:00 PM and 4:00 PM; or placebo at all three times in this randomized, double-blind, three-way crossover study. Impairment of mental performance was assessed by choice reaction time testing and digit symbol substitution scores. Drowsiness was self-assessed on the Stanford Sleepiness Scale and on a visual analog scale. Both antihistamines produced changes in digit symbol substitution, recognition time, and subjective assessments of sleepiness different from placebo. Expressed as change from baseline, the greatest reductions in digit symbol substitution scores after dimenhydrinate occurred 3 hours after the first dose (6.6 +/- 7) and were not different from the greatest measured change after meclizine (5.8 +/- 8), which occurred 9 hours after the dose was administered. Similar results were obtained with the other psychometric test scores. Self-rated sleepiness after dimenhydrinate was greatest 1 hour after the first dose, and was significantly greater than the largest degree of sleepiness after meclizine, which occurred at 7 hours after the dose. The effects of the first dose of dimenhydrinate on psychometric test scores were compared with the magnitude of the effects produced by subsequent doses. The magnitude of effect of the first dose of dimenhydrinate was significantly greater than the magnitude of effect produced by subsequent doses. The data suggest the possibility that acute tolerance to central nervous system impairment develops with multiple doses of dimenhydrinate.

Adolescent↗

PubMed1976

Conformational populations for antihistamines and antihypertensives in solution.

The conformations in aqueous solution were determined for the XCH2CH2N systems of some antihistamines (H1-receptor antagonists) and some adrenergic neuron blocking agents, including the antihypertensive drugs guanethidine and guanoclor. The rotameric species thought to be the pharmacologically active one is often not the only rotamer present in solution.

Antihypertensive Agents↗

PubMed1976

Carbon-13 magnetic resonance spectroscopy of drugs II: antihistamines.

The natural abundance carbon-13 magnetic resonance spectra of a series of antihistamines (pheniramine, chlorpheniramine, methapyrilene, tripelennamine, pyrilamine, and thonzylamine) were detemined using the pulse Fourier transform technique. The chemical shifts were assigned with the aid of long-range carbon-13-hydrogen coupling constants.

Carbon Isotopes↗

PubMed1976

Aggregation of antihistamines in aqueous solution: effect of counterions on self-association of pyridine derivatives.

The effects of electrolytes on the self-association of the antihistaminic drugs, tripelennamine hydrochloride, thenyldiamine hydrochloride, pyrilamine maleate, pheniramine maleate, chlorpheniramine maleate, and brompheniramine maleate, in aqueous solution were examined by light-scattering from tripelennamine bydrochloride and thenyldiamine hydrochloride in 0.154 mole of sodium chloride/kg and 0.150 mole of sodium maleate/kg indicated a micellar pattern of aggregation. Higher aggregation numbers and lower CMC's were determined in the presence of the maleate ion. No significant discontinuity in the concentration dependence of the light scattering of the remaining compounds in either of the two electrolytes was evident, and the aggregation of these compounds was treated using a stepwise association model. Values of the association constants and the limiting number of associating species were, in general, increased by the addition of electrolyte in the order water less than sodium chloride less than sodium maleate. An apparently nonmicellar pattern of aggregation could be induced by chemically changing the counterion from chloride to maleate.

Chemical Phenomena↗

PubMed1979

Ion-pair liquid chromatographic assay of decongestants and antihistamines.

The quantitative determinations of combinations of antihistamine and decongestant drugs including phenylephrine, dl-ephedrine, psi-ephedrine, phenylpropanolamine, pyrilamine, pheniramine, l-ephedrine, chlorpheniramine, brompheniramine, oxymetazoline, naphazoline, and antazoline contained in solid and liquid dosage forms are described. All active ingredients except the ephedrine optical isomers were separated from other ingredients with ion-paired high-pressure liquid chromatography. Manipulation of the mobile phase either by changing the hydroalcoholic ratio or by changing the alkyl chain length of the counterion (sulfonic acid) for achieving optimum separations is discussed. The method is simple, short, accurate, and precise.

Chromatography, Liquid↗

PubMed1982

pKa determination of benzhydrylpiperazine antihistamines in aqueous and aqueous methanol solutions.

The pKa1 and pKa2 values of three benzhydrylpiperazine antihistamines, cyclizine (I), chlorcyclizine (II), and hydroxyzine (III), were determined at 24.5 +/- 0.5 degrees by potentiometric titration in aqueous solution to be 2.16 +/- 0.02 and 8.05 +/- 0.03, 2.12 +/- 0.04 and 7.65 +/- 0.04, and 1.96 +/- 0.05 and 7.40 +/- 0.03, respectively. The pKa2 values were also determined by titration in seven aqueous methanol solutions in the range of 11.5-52.9% (w/w) methanol. The apparent dissociation constants of I-III in the aqueous methanol solutions, psKa2, were plotted according to two linear regression equations from which the values in water, p omega Ka2, were extrapolated. The plotted variables were psKa2 versus methanol concentration (%w/w) and psKa2 + log (water concentration, M) versus 1000/epsilon, where epsilon is the dielectric constant of the aqueous methanol solution. The maximum difference between pKa2 and p omega Ka2 was observed in the case of II where p omega Ka2 was 5.23% higher. Statistical analysis of the linear regression data obtained from the plots showed that slightly better accuracy (p less than 0.13) and correlation (p less than 0.16) were obtained, but the precision was essentially equal with both methods. The observed ratio of Ka1/Ka2 in I-III, 2.75 X 10(5)-7.76 X 10(5), was attributed to solven- and space-mediated field effects and electrostatic induction between nitrogen atoms in the piperazine ring.

Chemical Phenomena↗

PubMed1984

Bare silica as a reverse-phase stationary phase: liquid chromatographic separation of antihistamines with buffered aqueous organic mobile phases.

Unbonded silica gel is an effective support for reverse-phase liquid chromatographic separations of lipophilic amines. Simple buffered aqueous-organic mobile phases provide rapid isocratic separations of antihistamines. Phenylpropanolamine hydrochloride, chlorpheniramine maleate, and dextromethorphan hydrobromide are separated in 8 min on bare silica with a mobile phase of 75% methanol and 25% water which is 0.01 M in (NH4)2HPO4. Quantitation is reproducible. A wide variety of additional compounds may be separated using the same mobile phase.

Chromatography, Liquid↗

PubMed1988

Microbial transformation of the antihistaminic drug triprolidine hydrochloride.

The production of a known mammalian metabolite of the antihistamine triprolidine through fungal metabolic transformation has been demonstrated. The filamentous fungus Cunninghamella elegans ATCC 9245 was grown in Sabouraud dextrose broth containing triprolidine hydrochloride monohydrate. One major metabolite was extracted with methylene chloride, isolated by high-performance liquid chromatography, and identified by its proton-nuclear magnetic resonance and desorption chemical ionization mass spectral properties as hydroxymethyl triprolidine (2-[1-(4-hydroxymethylphenyl)-3-(1-pyrrolidinyl-1-propenyl)] pyridine). After 240 h of incubation, the hydroxymethyl derivative represented approximately 55.0% of the initial dose. Fungal oxidation of hydroxymethyl triprolidine to the corresponding carboxylic acid triprolidine derivative (also a known mammalian triprolidine metabolite) was not observed. No mutagenic activity was observed for triprolidine and hydroxymethyl triprolidine by reversion of Salmonella typhimurium strains TA97, TA98, TA100, and TA104 at concentrations up to 1000 and 200 micrograms/plate, respectively. These results suggest that the fungal metabolism of triprolidine to the hydroxymethyl derivative occurs predominantly through pathways which do not result in mutagenic activation. Incubation of C. elegans with triprolidine under an 18O2 atmosphere and subsequent electron impact mass spectral analysis of the hydroxymethyl triprolidine formed indicate that molecular oxygen was incorporated into the methyl group and suggest a mono-oxygenase catalyzed reaction. This study parallels previous studies on the mammalian metabolism of triprolidine and clearly indicates that the microbial transformation of triprolidine is a useful alternative for the synthesis of potential mammalian metabolites.

Animals↗

PubMed1994

Synthesis of N-heteryl-beta-[(2-alkoxyethyl)oxy]/beta-[[2-(N,N- dialkylamino)ethyl]oxy]acetamides as possible H1-antihistaminics.

The synthesis of beta-[2-(alkoxyethyl)oxy]- and beta-[[2-(N,N-dialkylamino)ethyl]oxy]acetamides containing an N-heteryl moiety is reported. Three heteryl systems, 2-phenyl/methyl-3,4-dihydro-4-oxoquinazolin-3- yl, 5-aryl-1,3,4-oxadiazol-2-yl, and 5-alkyl-1,3,4-thiadiazol-2-yl, were employed. Appropriate heterylamines were first converted into their respective chloroacetamides and then reacted with 2-alkoxyethanols/2-(N,N-dialkylamino)ethanols in dry acetone in the presence of anhydrous potassium carbonate to obtain the title compounds. Ten such new acetamides from each series were synthesized and characterized. Their in vitro antihistaminic activity was determined using the isolated guinea pig ileum method. The IC50 values of the compounds indicated correlations with their structural and electronic features.

Acetamides↗

PubMed2005

Antiallergic and antihistaminic effect of two extracts of Capparis spinosa L. flowering buds.

The antiallergic properties of two lyophilized extracts obtained from Capparis spinosa L. flowering buds (capers) by methanol extraction, carried out at room temperature (CAP-C) or with heating at 60 degrees C (CAP-H), were investigated. The protective effects of CAP-H and CAP-C, orally administered (14.28 mg[sol ]kg), were evaluated against Oleaceae antigen challenge-induced and histamine-induced bronchospasm in anaesthetized guinea-pigs. Furthermore, the histamine skin prick test was performed on humans, applying a gel formulation containing 2% CAP-C (the only extract able to protect against histamine-induced bronchospasm) on the skin for 1 h before histamine application and monitoring the erythema by reflectance spectrophotometry. The CAP-H showed a good protective effect against the bronchospasm induced by antigen challenge in sensitized guinea-pigs; conversely, a significant decrease in the responsiveness to histamine was seen only in CAP-C pretreated animals. Finally, the CAP-C gel formulation possessed a marked inhibitory effect (46.07%) against histamine-induced skin erythema. These two caper extracts displayed marked antiallergic effectiveness; however, the protective effect of CAP-H was very likely due to an indirect mechanism (for example, inhibition of mediator release from mast cells or production of arachidonic acid metabolites); conversely, CAP-C is endowed with direct antihistaminic properties. The different mechanisms of action of CAP-H and CAP-C may be related to a difference in the extraction procedure and, thus, in their qualitative[sol ]quantitative chemical profile.

Administration, Oral↗

PubMed2001

Second generation antihistamines in the treatment of seasonal allergic rhinitis due to Parietaria and cypress pollen.

Second generation antihistamines have been employed in the treatment of seasonal allergic rhinitis for many years. However, their effects on two distinctive Mediterranean allergic conditions, viz. Parietaria pollinosis and cypress pollinosis, have been scarcely investigated, so far. A comparative efficacy and side effect trial of astemizole and terfenadine in the treatment of seasonal allergic rhinitis due to either Parietaria or cypress pollen was carried out in 27 adult patients, according to a double-blind, double-dummy parallel-group design. Airborne pollen monitoring allowed comparison of symptom scores with pollen counts. Seven patients (26%) withdrew, due to poor symptom control. In contrast, in a subset of 15 patients who completed the trial, treatment led to a substantial and statistically significant decline in symptom severity in both the astemizole and the terfenadine study group. However, no statistically significant inter-group differences could be detected.

Adult↗