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PubMed2001

Duration of the antihistaminic effect after discontinuation of ebastine.

BACKGROUND: The inhibitory effect of antihistamines on allergen-induced skin reactions can impair the results of allergen skin testing, which are necessary for the diagnosis of atopic diseases. This study was designed to determine the time period required for the inhibitory effect of ebastine on allergen-induced skin reactivity to disappear completely. METHODS: This was a double-blind, placebo-controlled, parallel-group study including 23 out of 27 randomized patients. They received either ebastine 20 mg or placebo once daily for 7 days. At the end of treatment, allergen challenge was performed daily for 7 days. Histamine challenge was performed on day 1 (6 and 24 h) and day 5 after treatment. The wheal and flare surface areas were measured and analyzed. RESULTS: Highly significant inhibition of the wheal and flare response induced by allergen was observed after ebastine treatment on days 1 and 2 as compared with placebo (P < 0.01 for both). The inhibition was reduced, although still significant, by day 3 (P < 0.05). No significant difference was observed by day 4 between the ebastine and the placebo groups. The effects of histamine challenge were significantly reduced in the ebastine compared with the placebo group at day 1 (6 and 24 h), and were similar at day 5 after treatment. CONCLUSION: Our results show that the wheal and flare response to allergen after ebastine discontinuation returns to placebo values after 4 days. Therefore, patients using ebastine need to be antihistamine-free for 4 days before the skin prick test. This is valuable information for the allergologist seeking to diagnose allergen sensitivity.

Adolescent↗

PubMed2000

Functional neuroimaging of cognition impaired by a classical antihistamine, d-chlorpheniramine.

Antihistamine induced cognitive decline was evaluated using positron emission tomography (PET) measurement of histamine H1 receptor (H1R) occupancy and regional cerebral blood flow (rCBF). Cognitive performance in attention-demanding task deteriorated dose-dependently and the effects were statistically significant after the treatment of 2 mg of d-chlorpheniramine. There was no significant change in subjective sleepiness in the same dose. The regional blockade of H1R was observed mainly in the frontal, temporal and anterior cingulate cortices, and the intravenous administration of d-chlorpheniramine as a therapeutic dose (2 mg) blocked over 60% of H1R in the frontal cortices. The results from activation study using visual discrimination tasks demonstrated that enhanced activity in the right prefrontal and anterior cingulate cortices as well as a decreased activity in the left temporal and frontal cortices and midbrain after the treatment of d-chlorpheniramine. There were no changes in global CBF for the subjects treated with 2 mg d-chlorpheniramine (pre; 44.8+/-3.3 ml dl(-1) min(-1) vs post; 44.4+/-4.7 ml dl(-1) min(-1)). The results indicated that the attention system of human brain could be altered by therapeutic doses of H1R antagonists. These findings provide the information as to the potential risk of antihistamines in our daily activities. British Journal of Pharmacology (2000) 129, 115 - 123

Adult↗

PubMed1998

Determination of antihistamines based on the formation of mixed aggregates with surfactants.

The determination of antihistamines based on the measurement of the critical micelle concentration (c.m.c.) of mixed sodium dodecyl sulfate (SDS)-antihistamine aggregates is proposed. The dye Coomassie Brilliant Blue G (CBBG) was used as a photometric probe for the rapid determination of c.m.c.s. The micellar properties of these drugs permitted the determination of diphenhydramine, antazoline, tripelennamine, diphenylpyraline and clemizole at the micron level with detection limits ranging between 0.1 and 0.7 microns. Hence the proposed method surpassed existing alternative photometric methods used routinely in the quality control of these drugs in sensitivity and featured similar detection limits to fluorimetric methods. The relative standard deviation for 6 micron diphenhydramine was 3.7%. The method was applied to the determination of these drugs in pharmaceutical preparations (solutions, capsules, creams and pills). which were analyzed directly after dissolution of the samples in distilled water.

Antazoline↗

PubMed1997

Chloroquine-induced pruritus in malaria fever: contribution of malaria parasitaemia and the effects of prednisolone, niacin, and their combination, compared with antihistamine.

AIMS: Chloroquine treatment of malaria fever, results in a generalized pruritus of unknown mechanism in up to 60% of adult Africans, by contrast pruritus is unusual in Caucasians following chloroquine use. METHODS: We conducted a double-blind, randomized, parallel group study to examine and compare the antipruritic effects of promethazine, niacin, prednisolone and their combination on pruritus induced by chloroquine, in 28 historical itching patients with parasitologically proven malaria fever. We also evaluated the role of the antecedent malaria parasite density in the severity of chloroquine pruritus intensity. RESULTS: The concurrent administration of chloroquine (2.1 g base total dose) with prednisolone caused a statistically significant reduction in the pruritus AUC (0, 72 h) (P < 0.001 ANOVA) compared with the antihistamine promethazine alone. The areas under the pruritus intensity-time curve were promethazine 105 +/- 28 (units h), niacin 76 +/- 22, prednisolone 28 +/- 24, and prednisolone and niacin 34 +/- 17 (P < 0.001 ANOVA). The 95% confidence interval for the difference in the pruritus AUC between prednisolone and promethazine was 8.4 to 145.6 units h. There was a statistically significant and positive correlation between the pruritus intensity (AUC 0, 72 h) and the malaria parasite load in the itching subjects, not receiving prednisolone (n = 9) (r = 0.73, P = 0.026 ANOVA). CONCLUSION: A single oral dose of prednisolone (10 mg) may be preferable to the antihistamine promethazine (25 mg) as an antipruritic agent for concurrent prescription with chloroquine in individuals predisposed to severe itching. Malaria parasite clearance and clinical amelioration were unaffected by any of the treatments.

Adult↗

PubMed1999

The metabolism of antihistamines and drug interactions: the role of cytochrome P450 enzymes.

The non-sedating antihistamines show a diversity of fates in the body and the parent drugs and metabolites may differ in their biological properties. Clinically significant interactions with inhibitors of cytochrome P450 have been reported primarily for terfenadine, which has the potential for cardiac toxicity, and is metabolized to fexofenadine, an antihistamine without cardiac effects. Astemizole shares many of these characteristics and important safety-related interactions are likely. Loratadine undergoes extensive metabolism so that pharmacokinetic interactions could occur, but they would be of little clinical importance because of the lack of cardiac activity of the parent drug and its metabolites. Ebastine also undergoes pharmacokinetic interactions, the significance of which is dependent on clarification of the extent of any relevant cardiotoxicity of both ebastine and its metabolite. Interactions would not be clinically important for cetirizine and fexofenadine which do not show cardiac effects and are eliminated with little metabolism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

QT interval monitoring during clinical studies with mizolastine, a new H1 antihistamine.

BACKGROUND: Some H1 antihistamines are at risk for rare but severe dysrhythmias due to an effect on the ventricular repolarization. OBJECTIVE: To present an overview of the QT interval monitoring performed during the clinical development of mizolastine, a new selective second-generation H1 antihistamine. METHODS: The ECGs database analysis of clinical studies conducted in volunteers and patients is summarized and focused on the results of reported studies and studies specifically designed for the assessment of the effect of mizolastine on cardiac repolarization, through the QT interval measurements. Mizolastine was orally administered up to 75 mg single dose and 40 mg repeated dose in healthy volunteers (i.e. 7. 5 and 4 times the recommended dose, respectively) and at a dose of 10 or 15 mg in patients. RESULTS: In healthy volunteers, no increased incidence of QTc values >440 msec or DeltaQTc >/=40 msec were recorded compared to placebo. No dose-related increase in QTc interval was observed. The ECG parameters were not modified by the co-administration of mizolastine with digoxin, diltiazem and erythromycin, when compared to the effect of each co-administered drug alone. In patients, the mean QTc interval changes from baseline did not significantly differ from placebo. In comparative studies vs. loratadine a similar incidence of out of range values was observed with mizolastine and loratadine. CONCLUSION: ECG monitoring of volunteers and patients included in clinical studies conducted with mizolastine showed no significant effect of mizolastine on cardiac repolarization.

Benzimidazoles↗

PubMed2001

Antihistamines as analgesics.

Histamine activates pain-transmitting nerve fibres, releases pain-related neuropeptides, and is painful when injected into the skin. Histamine agonists mimic these effects, suggesting that histamine plays a role in mediating the signal transduction of tissue damage or other painful stimulus. Certain 'antihistamines' (histamine H1 receptor antagonists) and other antihistaminics are 'analgesic' in preclinical or clinical models. Potential sites of action of these agents include the brain and spinal cord and a specific histamine receptor subtype might be involved (three subtypes have been identified). However, it is possible that other mechanisms account for the analgesic effect.

Analgesia↗

PubMed1997

Antihistamine responsive cluster headache in a teenaged girl.

Episodic cluster headache is a well-recognized entity usually starting in the second decade of life. Uncommonly, the first typical symptoms may present in the first decade of life, but are rarely recognized as such during childhood. We report a 12-year-old girl who presented with a 1-year history of bouts of right-sided hemicrania with ipsilateral, clearly demarcated, redness and itching of the skin of the face, lasting from 15 minutes to 2 hours per day. The episodes recurred up to several times daily for a few days and were followed by remissions lasting up to 2 months. Thorough investigations failed to prove any definite cause. Antihistamine prophylaxis, first with astemizole and then with loratadine, proved to be very effective. During the follow-up period of more than 3 years, such a prophylactic regimen provided excellent relief, with only two relapses due to noncompliance. We suggest that in a sequential treatment trial for cluster headache during childhood, antihistamines should have their place, especially in those cases where clinical evidence may suggest histamine involvement.

Astemizole↗

PubMed1979

CNS effects of the antihistamines diphenhydramine and terfenadine (RMI 9918).

The quantitative EEG profile of a putative antihistaminic drug, terfenadine, was determined in a crossover comparison with diphenhydramine in normal male volunteers. Terfenadine failed to elicit the characteristic EEG or behavioral effects of sedative antihistaminics, and was distinguishable from diphenhydramine. The EEG profile confirmed the lack of CNS effect observed in preclinical and clinical trials.

Adult↗

PubMed1983

Lack of efficacy of a decongestant-antihistamine combination for otitis media with effusion ("secretory" otitis media) in children. Results of a double-blind, randomized trial.

In a double-blind, randomized trial of 553 infants and children who had otitis media with effusion ("secretory" otitis media), we compared the efficacy of a four-week course of an oral decongestant-antihistamine combination (pseudoephedrine hydrochloride, 4 mg per kilogram of body weight per day, and chlorpheniramine maleate, 0.35 mg per kilogram per day) with that of placebo. Among patients with initially unilateral disease, resolution of middle-ear effusion occurred at four weeks in 38 per cent of those treated with placebo and 34 per cent of those treated with drug (P = 0.74). Among patients with initially bilateral disease the corresponding proportions were 19 and 21 per cent, respectively (P = 0.67). Side effects were reported more often among drug-treated than placebo-treated patients. Decongestant-antihistamine combinations do not appear to be indicated for the treatment of otitis media with effusion in infants and children.

Child↗

PubMed2003

Pregnancy outcome after gestational exposure to loratadine or antihistamines: a prospective controlled cohort study.

BACKGROUND: Loratadine is a second-generation histamine H(1)-receptor antagonist, used in the treatment of allergic conditions. No prospective controlled trials on loratadine in human pregnancy have been published to date. OBJECTIVE: To determine whether the use of loratadine or other antihistamines (OAH) is associated with an increased risk of major anomalies. METHODS: Callers who were counseled by the Israeli Teratogen Information Service in regard to loratadine or OAH exposure during pregnancy were prospectively collected and followed up. Pregnancy outcome was compared among three exposure groups: loratadine, OAH, and a control group of patients who were counseled for nonteratogenic exposure, nonteratogenic controls (NTC). The OAH included astemizole, chlorpheniramine, terfenadine, hydroxyzine, promethazine, and dimetindene. RESULTS: We followed up 210 pregnancies exposed to loratadine (77.9% in the first trimester) and 267 pregnancies exposed to OAH (64.6% in the first trimester) and compared pregnancy outcome with that of 929 NTC. The rate of congenital anomalies did not differ among the groups [loratadine: 4/175 (2.3%), OAH: 10/247 (4.0%), NTC: 25/844 (3.0%), P =.553, relative risk (RR), 0.77; 95% confidence interval (CI), 0.27 to 2.19, (loratadine vs NTC); RR, 0.56; 95% CI, 0.18 to 1.77, (loratadine vs OAH)]. The rate did not differ between those exposed to antihistamines in the first trimester and the control patients [loratadine: 1/126 (0.8%), OAH: 7/146 (4.8%), NTC: 25/844 (3.0%), P =.152, RR, 0.27; 95% CI, 0.04 to 1.94, (loratadine vs NTC); RR, 0.17; 95% CI, 0.02 to 1.33, (loratadine vs OAH)]. CONCLUSIONS: This study on the use of loratadine in human pregnancy suggests that this agent does not represent a major teratogenic risk. The study was powered to find a 3-fold increase in the overall rate of major anomalies.

Abnormalities, Drug-Induced↗

PubMed1998

Antiinflammatory properties of cetirizine in a human contact dermatitis model. Clinical evaluation of patch tests is not hampered by antihistamines.

The aim of this double-blind, placebo-controlled, randomized, cross-over pilot study was to assess the antiinflammatory properties of cetirizine. A group of 27 patients with a positive patch test to an allergen consecutively received cetirizine 10 mg o.d. or placebo during a 14-day period, respectively. At day 11 of each period, patch testing was performed with the allergen. The image analysis showed a skin reaction significantly reduced under cetirizine (p = 0.03), but the clinical recording and the standardized chromatometry did not show any difference between groups. In the cross-over analysis the results of image analysis were influenced by the period, but this effect disappeared after adjustment of the ambient temperature during the 3 days of the test. These results demonstrate that cetirizine has an impact on the inflammatory process in a clinical model of cell-mediated allergic reaction, although this effect is only detected with a very sensitive technique. They also show that it is useless to stop antihistamines before patch testing, since clinical evaluation of tests is not hampered by a potent antihistamine. Additionally this study suggests that ambient temperature has an influence on the results of tests.

Adult↗

PubMed1976

Multiple infection with Toxocara canis. Influence of antihistamines and corticosteroids on the histopathological response.

The histopathology of the tissues of mice infected with ten doses of 100 embryonated eggs of Toxocara canis and the influence of antihistamines and corticosteroids on these findings is described. The main lesions were confined to the liver and lungs. In infected but untreated control mice hepatic lesions consisted of periportal infiltrates, widespread foci of liver cell necrosis and polymorphonuclear and mononuclear accumulation and a few fibrotic granulomata. Treatment with antihistamines did not change these findings significantly, but corticosteroids decreased the amount of cellular infiltration and the size of the lesions. Pulmonary lesions consisted mostly of confluent infiltrates of polymorphonuclears, eosinophils and mononuclear cells with some macrophage proliferation. Neither drug seemed to affect the lung involvement.

Amidines↗

PubMed1990

The chemotherapy of rodent malaria. XLV. Reversal of chloroquine resistance in rodent and human Plasmodium by antihistaminic agents.

The inherent blood schizontocidal activities of five antihistaminic compounds, cyproheptadine hydrochloride (CYP), ketotifen hydrogen fumarate (KET), pizotyline hydrogen maleate (PIZ), azatadine maleate (AZAT) and loratadine (LOR) were examined against the following organisms: chloroquine-sensitive (CS) Plasmodium berghei and chloroquine-resistant (CR) P. yoelii ssp. NS in mice; and CS Tak 9 clone 96 and CR K1 strain of P. falciparum in vitro. Chloroquine, verapamil and desipramine were used as comparison standards. CYP, KET, PIZ were active against the CS strain in vivo with ED90 levels between 20 and 30 mg kg-1 (given sc daily for four days). They were slightly more active against the CR strain. AZA was active, but much less so than the other compounds. LOR, verapamil and desipramine were inactive in vivo at the doses tested. Against CS P. falciparum in vitro, all five antihistaminics and desipramine were active at EC50 concentrations ranging from about 50-80 mumol l-1, while verapamil was only active at 175 mumol l-1. Against the CR strain of this parasite, CYP, PIZ and LOR were slightly more active than against the CS strain, but KET, AZAT, desipramine and verapamil were significantly less active. The action of all these compounds in combination with chloroquine was then examined both in vivo and in vitro. The ability of verapamil and desipramine to reverse chloroquine resistance in vitro was confirmed, but only a low level of reversal was seen with these compounds in vivo. However, CYP, KET, PIZ and AZAT produced a marked reversal of chloroquine resistance both in vivo and in vitro. The implications of these observations in relation to further laboratory and clinical research are discussed.

Animals↗

PubMed2000

The chemotherapy of rodent malaria. LIX. Drug combinations to impede the selection of drug resistance, Part 3: Observations on cyproheptadine, an antihistaminic agent, with chloroquine.

Several compounds in current clinical use as antihistaminic agents, among them cyproheptadine (CYP), have been shown, in experimental models, to reverse resistance of the asexual, intra-erythrocytic stages of rodent or human malarial parasites to chloroquine (CQ). Although preliminary clinical trials with CYP failed to confirm such activity in subjects with naturally acquired infection with Plasmodium falciparum, Nigerian investigators have reported that another antihistaminic, chlorpheniramine, significantly restores the blood schizontocidal action of CQ in semi-immune patients with CQ-resistant P. falciparum, when the two compounds are administered together. The rates at which resistance to CYP can be produced, in mice infected either with CQ-resistant P. yoelii ssp. NS or CQ-resistant P. yoelii nigeriensis, when drug-selection pressure is exerted with this compound alone have now been compared with the rate and extent to which resistance develops in infected animals that are treated with various combinations of CYP and CQ. The data indicate that, in both parasites, stable resistance develops slowly to CYP alone and that exposure to a combination of CYP plus CQ significantly impedes the selection of resistance to CYP. Although the antimalarial action of CYP is reported to extend to the pre-erythrocytic hepatic stages, there was no evidence of gametocytocidal activity in the present study. The future implications of these observations are discussed in relation to the clinical potential of CYP + CQ and similar combinations and possible future research.

Animals↗

PubMed1999

Risk of breast cancer according to use of antidepressants, phenothiazines, and antihistamines.

In laboratory studies, some antidepressants caused increased growth of mammary tumors. The relation of use of these drugs to the development of breast cancer was examined in a hospital-based case-control study. Information, including lifetime medication history, was collected by interview from 5,814 women with primary breast cancer diagnosed within the previous year, 5,095 women with primary malignancies of other sites, and 5,814 women with other conditions. Relative risks were estimated by using unconditional multiple logistic regression for regular use (> or =4 days per week for > or =4 weeks beginning > or =1 year before admission) of antidepressants and structurally similar drugs. With reference to never use of each drug, relative risks were statistically compatible with 1.0 for selective serotonin reuptake inhibitors (SSRI), tricyclics, other antidepressants, phenothiazines, and antihistamines; results were very similar using both control groups. There were no significant increases in risk for any category of regular use, stratified according to cumulative duration of use or time interval since the most recent use or for any individual drug within the broader classes. However, the estimate for regular SSRI use in the previous year, 1.8, was of borderline statistical significance (95% confidence interval: 1.0, 3.3). The findings do not support an overall association between the use of antidepressants, phenothiazines, or antihistamines and breast cancer. However, the results for SSRIs are not entirely reassuring.

Adult↗

PubMed1997

Alkylamine antihistamine toxicity and review of Pediatric Toxicology Registry of the National Association of Medical Examiners. Report 4: Alkylamines.

Antihistamines are popular nonprescription medications for the treatment of allergy and cold symptoms. Accidental exposures to these preparations are common with > 14,000 occurring annually in children under the age of 6 years (1). Despite this, there is limited information about toxic and lethal concentrations of these drugs in children. We present a case of a pediatric fatality due to a common brompheniramine and phenylpropanolamine preparation and review available Pediatric Toxicology Registry data on alkylamine antihistamines. The data collected by the Pediatric Toxicology Registry on the drug phenylpropanolamine has been previously reported (2). A review of the Registry data suggests that postmortem blood brompheniramine concentrations of 0.4 mg/L and greater in children is indicative of brompheniramine poisoning. However, pheniramine was also present in the blood in the same case and may have caused an additive effect. The data are insufficient to establish the threshold of fatal blood pheniramine concentration in children. Data for chlorpheniramine are lacking.

Brompheniramine↗

PubMed2003

Transitioning the second-generation antihistamines to over-the-counter status: a cost-effectiveness analysis.

BACKGROUND: A U.S. Food and Drug Administration advisory committee deemed the second-generation antihistamines (SGA) safe for over-the-counter use against the preliminary opposition of the manufacturers. As a result, loratadine is now available over-the-counter. First-generation antihistamines (FGA) are associated with an increased risk of unintentional injuries, fatalities, and reduced productivity. Access to SGA over-the-counter could result in decreased use of FGA, thereby reducing deleterious outcomes. The societal impact of transitioning this class of medications from prescription to over-the-counter status has important policy implications. OBJECTIVE: To examine the cost-effectiveness of transitioning SGA to over-the-counter status from a societal perspective. RESEARCH DESIGN: A simulation model of the decision to transition SGA to over-the-counter status was compared with retaining prescription-only status for a hypothetical cohort of individuals with allergic rhinitis in the United States. Estimates of costs and effectiveness were obtained from the medical literature and national surveys. Sensitivity analysis was performed using a second-order Monte Carlo simulation. MAIN OUTCOME MEASURES: Discounted, quality-adjusted life-years saved as a result of amelioration of allergic rhinitis symptoms and avoidance of motor vehicle, occupational, public and home injuries and fatalities; discounted direct and indirect costs. RESULTS: Availability of SGA over-the-counter was associated with annual savings of 4 billion dollars (2.4-5.3 billion dollars) or 100 dollars (64-137 dollars) per allergic rhinitis sufferer and 135,061 time-discounted quality-adjusted life years (84,913-191,802). The sensitivity analysis provides evidence in support of these results. CONCLUSION: Making SGA available over-the-counter is both cost-saving and more effective for society, largely as a result of reduced adverse outcomes associated with FGA-induced sedation. Further study is needed to determine the differential impact on specific vulnerable populations.

Accidents↗