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PubMed1994

Liquid chromatography of antihistamines using post-column tris(2,2'-bipyridine) ruthenium(III) chemiluminescence detection.

The separation and detection of five antihistamine drugs commonly found within over-the-counter allergy and cold pharmaceutical products was performed by HPLC with chemiluminescence (CL) detection. Comparable detection limits at 5-10 pmol were found for the antihistamines by both UV at 214 nm and tris(2,2'-bipyridine) ruthenium(III) CL. However, urine samples were found not to generate as large an unretained peak by CL detection as compared to those peaks by UV detection at 214 and 254 nm. For example, the pheniramine peak representing 0.15 microgram/ml was almost totally obscured at 214 nm. Quantitative results received for three antihistamine commercial samples ranged from 4 to 8% error in accuracy when an internal standard was used to compensate for short term detector drift.

2,2'-Dipyridyl↗
PubMed1977

The effect of topical antihistamine on the initial pulpal inflammatory response of monkey teeth.

Cavity preparations were made in sixty sound teeth of healthy monkeys. Thermal trauma was delivered to the pulps of all teeth through application of a heated soldering iron to the floor of a cavity preparation. Fifteen teeth were randomly designated as controls and were restored immediately with zinc oxide and eugenol. Forty-five teeth were designated as test teeth. These were treated topically with a 4 per cent antihistamine solution and restored with zinc oxide and eugenol. Histologic sections were prepared to show the effect of the antihistamine on the thermally initiated inflammatory response during the postoperative period. No significant difference was observed in the inflammatory reactions of treated or untreated pulps. A 4 per cent aqueous solution of topically applied antihistamine did not appear to be of any significant value in obviating pulpal inflammation.

Animals↗
PubMed1982

Significance of H1 and H2 receptors in the human nose: rationale for topical use of combined antihistamine preparations.

The aim of this experiment was to study the importance of histamine H1 and H2 receptors in the human nose. We therefore provoked 25 healthy human subjects with histamine after local pretreatment with the H1 receptor antagonist, chlorpheniramine maleate, the H2 receptor antagonist, ranitidine hydrochloride, and a combination of these two antihistamines. The histamine-induced increase in nasal airway resistance was 52% inhibited by combined use of the two antihistamine sprays (p less than 0.05), 22% by chlorpheniramine alone (p less than 0.05), and 29% by ranitidine. The two sprays together were significantly better than the H1 antagonists alone (p less than 0.05). These results suggest an equal importance of H1 and H2 receptors in nasal blood vessels, and an additive effect of H1 and H2 antihistamines. Although chlorpheniramine effectively blocked tickling and the reflex-mediated symptoms, sneezing and hypersecretion, ranitidine had no effect, which suggests an H1 and not an H2 effect on sensory nerve endings in the airway epithelium.

Administration, Topical↗
PubMed1985

Astemizole and other H1-antihistaminic drug treatment of asthma.

The disparity between the activation of mast cells in the airways of patients with allergic asthma and the lack of efficacy of H1-antihistamines in asthma therapy has been difficult to reconcile. Histamine causes bronchoconstriction when inhaled by subjects with asthma and is released in detectable amounts into the circulation after bronchial provocation with an antigen. However, it is only weakly antagonized at bronchial H1-receptors by conventional antihistamines such as chlorpheniramine and clemastine, achieving dose ratios of 2 to 4 at maximally tolerated doses. Astemizole and terfenadine are two new H1-histamine antagonists with greatly increased potency and no sedative and anticholinergic side effects. Astemizole has a delayed onset of maximal activity but induces prolonged H1-blockade that extends 15 to 30 days after the end of treatment, whereas terfenadine has a rapid onset of action with a much shorter duration of effect. With therapeutic doses (10 mg/day), astemizole is at least four times more potent in antagonizing histamine-induced bronchoconstriction than the previously available H1-antihistamines and also effectively antagonizes antigen-induced bronchoconstriction in asthma. Astemizole has been shown to be highly effective in the symptomatic treatment of seasonal allergic rhinoconjunctivitis, with the exception of nasal obstruction. With continued treatment, astemizole also offers useful protection from the symptoms of seasonal asthma. Thus the role of histamine in the pathogenesis of asthma should be reappraised. Potent H1-histamine antagonists such as astemizole and terfenadine may offer some benefit in asthma therapy, but the precise clinical indications for their use will require critical evaluation.

Astemizole↗
PubMed1992

Antiallergic properties of the second-generation H1 antihistamines during the early and late reactions to antigen.

Some of the second-generation H1 antihistamines reduce the bronchoconstrictor response after exercise and antigen challenge. For example, terfenadine causes a slight but significant increase in forced expiratory volume after 1 second. At doses of 120 and 240 mg, terfenadine has a protective effect against asthma induced by ultrasonic nebulized distilled water and cold air hyperventilation challenge. Certain other newer antihistamines, such as ketotifen, azelastine, and cetirizine, have additional antiallergy properties. These effects include inhibition of eosinophil, basophil, and neutrophil migration and platelet-activating factor-induced eosinophil accumulation in skin. The ability of cetirizine (and perhaps other antihistamines) to inhibit these responses at usual therapeutic doses may be useful in investigating the late allergic reaction.

Antigens↗
PubMed1986

Clinical efficacy of antihistaminics as analgesics.

This paper reviews the clinical information on antihistaminic agents as analgesics and as analgesic adjuvants. The evidence indicates a direct analgesic effect of various antihistaminics. In clinical studies, diphenhydramine, hydroxyzine, orphenadrine and pyrilamine have been shown to produce analgesia as simple entities but chlorpheniramine has not and results with phenyltoloxamine have been equivocal when tested alone. Analgesic adjuvant effects of several antihistaminics have been reported. Clinically, orphenadrine and phenyltoloxamine have shown adjuvant effects with acetaminophen and aspirin. The mechanism of action remains speculative. The most recent trends in the classification of histamine receptors and how these receptors may interact with pain modulation are also considered.

Analgesics↗
PubMed1991

Effects of antihistaminics on locomotor activity in mice. Comparison with opiate and amphetamine-induced hyperactivity.

1. Three histamine H1-receptor antagonists (tripelennamine, diphenhydramine and cyclizine) and two H2-receptor antagonists (ranitidine and cimetidine)--1 and 10 mg/kg--were tested alone or in combination with the opioid partial agonist buprenorphine (1 mg/kg), the opioid antagonist naloxone (1 mg/kg) or dextroamphetamine (3 mg/kg) on locomotor activity in mice. 2. All three H1-antihistaminics tested and the H2-antihistaminic, cimetidine, enhance locomotor activity in a dose-dependent manner. 3. Furthermore, tripelennamine, diphenhydramine, cyclizine, ranitidine and cimetidine potentiate the buprenorphine-induced hyperactivity. 4. Previous administration of naloxone blocks the tripelennamine- and diphenhydramine-induced hyperactivity. 5. On the other hand, none of antihistaminics tested modifies the amphetamine-induced locomotor stimulation. 6. These results suggest that H1- and H2-receptor antagonists effects on locomotor behavior in mice may be related with opioid mechanisms, but not with amphetamine mechanisms.

Animals↗
PubMed1996

A combination therapy of psychotropic drugs and antihistaminics or antiallergics in patients with chronic urticaria.

The efficacy of psychotropic drugs in combination with antihistaminics or antiallergics in patients with chronic urticaria was investigated. Forty patients, who had had urticaria for at least one month and showed insufficient suppression of symptoms for more than one month while being treated with antihistaminics or antiallergics, were divided into two groups on the basis of their score on three kinds of psychological tests: a manifest anxiety test, a self-rating depression scale and the Cornell medical index. One group had a high score, the other a low score. We investigated both groups with or without psychotropics in combination with antihistaminics or antiallergics. Incidence of urticaria and degree of improvement were examined after 2 and 6 months. There was no statistical difference between the groups after 2 months. After 6 months, the members of the low-score group treated with psychotropics showed a little better prognosis than those not treated. However, the high-score group treated with psychotropics showed a statistically significant decrease of incidence and increase in degree of improvement (P < 0.01). In conclusion, it is suggested that a long-term combination therapy with psychotropics is effective in suppressing urticaria for patients who are anxious, depressive and psychosomatic symptom-prone, and moderately effective for those with a low score in these areas.

Adult↗
PubMed2006

The proarrhythmic antihistaminic drug terfenadine increases spontaneous calcium release in human atrial myocytes.

Spontaneous calcium release from the sarcoplasmic reticulum in cardiac myocytes plays a central role in cardiac arrhythmogenesis. Compounds intended for therapeutical use that interfere with intracellular calcium handling may therefore have an undesired proarrhythmic potential. Here we have used isolated human atrial myocytes to compare the effect of the proarrhythmic antihistaminic drug terfenadine with the non-proarrhythmic antihistaminic drugs fexofenadine and rupatadine on intracellular calcium homeostasis. Perforated patch-clamp technique was used to measure ionic currents and to detect spontaneous calcium release from the sarcoplasmic reticulum. Our results show that the compound terfenadine, with known arrhythmogenic effects, inhibits L-type calcium current (I(Ca)) with an IC(50) of 185 nM when cells are stimulated at 1.0 Hz. The inhibitory effect of 0.3 muM terfenadine increased from 19+/-4% at stimulation frequency of 0.2 Hz to 63+/-6% at 2.0 Hz. Moreover, terfenadine also increased spontaneous calcium release from the sarcoplasmic reticulum. At a concentration of 1 muM, terfenadine significantly increased the spontaneous Na-Ca exchange current (I(NCX)) frequency from 0.48+/-0.25 to 1.93+/-0.67 s(-1). In contrast, fexofenadine and rupatadine did not change I(Ca) or the frequency of spontaneous I(NCX). We conclude that the proarrhythmic antihistaminic drug terfenadine alters intracellular calcium handling in isolated human atrial myocytes. This experimental model may be suitable to screen for potential arrhythmogenic side-effects of compounds intended for therapeutical use.

Arrhythmias, Cardiac↗
PubMed2002

Role of antihistamines in ocular allergy.

Although H(1) antihistamines are commonly used to treat allergic disorders and have demonstrated efficacy in allergic rhinoconjunctivitis, data on the effects of these agents specifically on ocular symptoms are limited. Oral H(1) antihistamines inhibit some symptoms of pruritus and erythema in laboratory models and have been shown to be superior to placebo for relief of symptoms in clinical trials. Eye drops typically provide faster relief of ocular symptoms than oral agents, and combination therapy with a topical agent and an oral agent has been found to be superior to the oral agent alone. In general, oral H(1) antihistamines have been considered superior to intranasal corticosteroids for relief of ocular symptoms, but some studies have shown equal efficacy for these agents, or even superior efficacy for intranasal corticosteroids.

Eye Diseases↗
PubMed1984

Trace analysis of the antihistamines methapyrilene hydrochloride, pyrilamine maleate and triprolidine hydrochloride monohydrate in animal feed, human urine and wastewater by high-performance liquid chromatography and gas chromatography with nitrogen-phosphorus detection.

Toxicological evaluation of the antihistamines methapyrilene hydrochloride, pyrilamine maleate, and triprolidine hydrochloride monohydrate using methapyrilene hydrochloride as the positive indicator was investigated as part of a structure-activity relationship study in rats and mice. Prerequisites for the toxicological tests were the development of analytical procedures to certify the dose, homogeneity and stability of the drugs in animal feed and to monitor human urine for possible exposure and to ensure removal of the test agents from wastewater prior to its discharge into the environment. A high-performance liquid chromatographic (HPLC) system was developed using a fluorescence detector for the determination of methapyrilene hydrochloride and pyrilamine maleate in feed at levels as low as 100 ng/g and in human urine as low as 1 ng/g. An HPLC-UV procedure was developed for the determination of triprolidine hydrochloride monohydrate in feed at levels as low as 10 micrograms/g. Data concerning p-values, extraction efficiencies from feed and stability experiments in feed are presented for these antihistamines. A gas chromatographic procedure using a nitrogen-phosphorus detector was also developed for determining the three antihistamines in admixture in wastewater at levels as low as 10 ng/g.

Animal Feed↗
PubMed1991

Effectiveness of an antihistamine-decongestant combination for young children with the common cold: a randomized, controlled clinical trial.

We tested the hypothesis that antihistamine-decongestant combinations cause no clinically significant relief of the symptoms of upper respiratory tract infections in young children by randomly assigning 96 children to one of three treatment groups: antihistamine-decongestant, placebo, and no treatment. There were no differences among the three study groups in the proportion of children considered "better" overall by the parent 48 hours after the initial assessment (drug, 67%; placebo, 71%; no treatment, 57%; p = 0.53). There were no differences among groups in individual or composite symptom score changes. Two thirds of parents whose children were eligible for the drug trial believed that their child needed medicine for cold symptoms. In the proportion of parents believing that their child needed medicine, there was no difference between those who consented to participate and those who refused. Parents who wanted medicine at the initial visit reported more improvement at follow-up, regardless of whether the child received drug, placebo, or no treatment. We conclude that there is no clinically significant improvement in symptoms of upper respiratory tract infection, including no significant placebo effect, in young children for whom an antihistamine-decongestant is prescribed.

Brompheniramine↗
PubMed1990

Pharmacology of antihistamines.

Unlike the classic antihistamines, the new H1-receptor antagonists do not block cholinergic or central H1 receptors and thus do not produce the side effects, such as sedation, impaired psychomotor performance, and excessive mucosal drying, that are commonly associated with the older agents. Important pharmacokinetic and pharmacodynamic differences that exist among this class of antihistamines translate into varying pharmacologic effectiveness. Terfenadine, loratadine, and cetirizine are all rapidly absorbed in healthy and allergic volunteers (peak plasma levels, 2 to 5 hours); astemizole, however, has an initial distribution phase of 2 to 3 days. Further, astemizole has the longest time to relief of symptoms in this class; histamine wheal inhibition is not apparent until the second day of 10 mg dosing and does not peak for 9 to 12 days. In comparison, terfenadine's antihistaminic action peaks at 3 to 4 hours, loratadine's at 4 to 6 hours, and cetirizine's at 4 to 10 hours. However, whereas the recommended dose of loratadine (10 mg) confers 50% wheal inhibition, 60 mg terfenadine produces an 85% to 90% inhibition. In addition, loratadine and cetrizine have apparent dose-related sedative effects.

Astemizole↗
PubMed1990

The role of antihistamines in atopic dermatitis.

Although several lines of evidence support a role for histamine in the pathogenesis of atopic dermatitis, antihistamines have generally offered only marginal therapeutic benefit. The efficacy of the classic antihistamines has been severely limited by sedative effects, demonstrating the need for improved, nonsedating agents. Multifunctional antihistamines, or third-generation "antiallergic" drugs, appear to offer a variety of advantages beyond their ability to inhibit histamine release, such as inhibition of mediator release and interference with eosinophil migration. Double-blind studies of high-dose regimens are needed to help clarify the therapeutic efficacy of these antiallergic drugs.

Basophils↗
PubMed1990

A review of the effects of antihistamines on mental processes related to automobile driving.

The newer, second-generation H1-receptor antagonists have been shown to have potent antiallergic effects without inducing sleepiness. However, because traditional antihistamines may cause functional or cognitive impairment, the clinician still must consider warning patients about activities that could be hazardous. Because the effects of drugs on driving an automobile are difficult to measure directly, studies must use surrogate activities in a laboratory setting. Effects of antihistamines on the central nervous system are assessed with psychomotor tests, which are selected on the basis of their relativity to real-world activities, to develop a profile of mental processes that may be affected. This article reviews the psychomotor tests and study design used to characterize the intensity and duration of drug effects after single and multiple doses and in combination with other impairing agents such as ethanol. Several studies have been published that assess the effects of cetirizine, an H1-receptor blocker, on mental performance. In the study discussed here, diphenhydramine hydrochloride and hydroxyzine were used as positive controls to demonstrate that the period during which some traditional antihistamines impair performance is different than the period of reported drowsiness they induce. The results of this series of studies show that cetirizine induced minimal changes in mental performance tests and only following the highest (20 mg) dose studied.

Automobile Driving↗
PubMed1983

Antihistamines and sedation.

With careful use of antihistamines central effects may be minimised or even largely avoided while adequate peripheral antihistaminic activity is preserved. Tolerance to central effects may develop quickly with some drugs, so that sedation is no longer troublesome after a few days. With sustained-release antihistamines, early-evening dosage may provide sufficient activity, without sedation, the next day. For patients in whom daytime sedation is troublesome three drugs, astemizole, mequitazine, and terfenadine, are likely to prove useful. However, the response of the individual patient cannot be predicted, and the possibility of sedation can never be completely excluded.

Astemizole↗
PubMed1999

Second-generation antihistamines: the risk of ventricular arrhythmias.

Some second-generation antihistamines, notably terfenadine and astemizole, have been associated with prolongation of the QT interval and the development of torsades de pointes, a potentially fatal ventricular arrhythmia. This rare adverse event has been associated with greatly elevated blood levels of these agents, resulting from drug overdose, hepatic insufficiency (dysfunction), or interactions with other drugs that inhibit their metabolism. This paper reviews the data concerning the effects of selected second-generation antihistamines on cardiac conduction, particularly the QT interval, to evaluate whether ventricular arrhythmias are a class effect of these agents. Electrocardiographic studies indicate that terfenadine and astemizole, but not loratadine or cetirizine, prolong the QT interval in laboratory animals. In vitro studies demonstrate that terfenadine and astemizole block the cardiac K+ channels, leading to delayed ventricular repolarization and QT-interval prolongation; in contrast, neither loratadine nor its metabolite, desloratadine, significantly inhibits cardiac K+ channels at clinically achievable blood levels. Studies in human volunteers confirm the absence of electrocardiographic effects of azelastine, cetirizine, fexofenadine, and loratadine administered at several times the recommended dose or concomitantly with agents that inhibit their metabolism and elimination. In conclusion, the data indicate that the potential to cause ventricular arrhythmias is not a class effect of second-generation antihistamines and that loratadine, cetirizine, azelastine, and fexofenadine are not associated with torsades de pointes or other ventricular arrhythmias.

Animals↗
PubMedDate not supplied

Sedative effects of antihistamines: safety, performance, learning, and quality of life.

Antihistamines are frequently part of the treatment regimen for seasonal and perennial allergic rhinitis occurring alone or in conjunction with associated airway disorders, such as asthma, sinusitis, and otitis media with effusion. These agents are also frequently prescribed for the treatment of urticaria to eliminate the need for long-term corticosteroids. This paper reviews the side-effect profile of the sedating and nonsedating agents (a classification given these drugs by the US Food and Drug Administration) in terms of patient satisfaction and quality-of-life parameters. Because the sedating antihistamines cross the blood-brain barrier more quickly and easily than the nonsedating antihistamines, they produce more central nervous system (CNS) effects, further exacerbating the decreases in decision-making, verbal learning, and psychomotor skills already experienced by the patient with allergic rhinitis. In contrast the now-preferred nonsedating agents do not readily cross the blood-brain barrier, do not produce CNS side effects, and, therefore, do not cause sedation or performance impairment. The nonsedating agents provide a safer alternative for patients with allergic rhinitis. Their use can increase patient satisfaction with the health care received.

Cognition↗