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PubMed1993

Comparison of azelastine and chlorpheniramine in the treatment of mastocytosis.

BACKGROUND: Azelastine, a novel antiallergic medication, was compared with chlorpheniramine maleate for efficacy and safety in the treatment of systemic mastocytosis. METHODS: Fifteen subjects with mastocytosis participated in a double-blind, randomized, three-period, crossover trial, which compared an azelastine regimen of 4 mg or 8 mg every 12 hours with a chlorpheniramine regimen of 12 mg every 12 hours. Response to therapy was assessed by daily symptom scores, extinction dilution skin tests, plasma histamine levels, and global evaluations. RESULTS: Subjects' mean wheal area responses provoked by histamine or morphine sulfate were significantly lowered by azelastine when compared with chlorpheniramine. Plasma histamine levels in subjects receiving azelastine or chlorpheniramine were not significantly different. There were no significant differences between azelastine and chlorpheniramine in individual symptom scores or global evaluations except that azelastine at both doses significantly relieved pruritus and at 4 mg significantly relieved abdominal pain and that chlorpheniramine was associated with less fatigue in comparison to azelastine at 8 mg. CONCLUSIONS: It thus appears that azelastine is superior to chlorpheniramine in suppressing skin responses to histamine and morphine sulfate and in suppressing pruritus in patients with mastocytosis. However, when all parameters are considered, neither drug is clearly superior for the treatment of patients with mastocytosis.

Adult↗
PubMed1992

The optical resolution of racemic chlorpheniramine and its stereoselective pharmacokinetics in rat plasma.

An ovomucoid-conjugated column has been developed for the chiral stationary-phase liquid chromatographic resolution of racemic chlorpheniramine with a quantitation limit of 0.05 microgram mL-1. The assay was used to study the stereoselective kinetics of chlorpheniramine enantiomers in rats. After bolus intravenous administration of racemic chlorpheniramine maleate (20 mg kg-1), plasma concentration of the (-)-form was higher than that of the (+)-form. In the elimination phase, the concentrations of (+)- and (-)-chlorpheniramine in the plasma declined biexponentially with half-lives of 18.2 and 50.0 min, respectively. Although there was no significant difference in blood-to-plasma concentration ratio of both enantiomers, the apparent total blood clearance of (+)-chlorpheniramine was twice as large as that of the (-)-isomer. Binding of (-)-chlorpheniramine to rat plasma protein was stronger than that of (+)-chlorpheniramine suggesting stereoselective pharmacokinetics may be due to a difference in the plasma protein binding.

Animals↗
PubMed2000

Prevalence of chlorpheniramine in aviation accident pilot fatalities, 1991-1996.

BACKGROUND: Chlorpheniramine is known to cause drowsiness, and this side effect has a potential to impair performance and could be a factor in accidents. METHODS: Therefore, to establish the prevalence of this drug in pilot fatalities of aviation accidents, a postmortem toxicology database--maintained at the Civil Aeromedical Institute--was examined for the presence of chlorpheniramine in the fatalities, occurred during 1991-1996. RESULTS: There were 47 (2.2%) accidents involving chlorpheniramine. Of these, 16 had only chlorpheniramine at 109 ng.ml-1 (n = 4) in blood and 1412 ng.g-1 (n = 12) in liver. Other drugs were also present in the remaining 31 cases, wherein chlorpheniramine concentrations were 93 ng.ml-1 (n = 18) in blood and 747 ng.g-1 (n = 12) in liver. Ninety-five percent of all quantitated blood values were at or above the therapeutic level (10 ng.ml-1), giving a 100 ng.ml-1 (n = 21) mean blood value. The drug's mean liver concentration from all cases was 1080 ng.g-1 (n = 24). The average blood value was approximately 10 times higher than the therapeutic value. CONCLUSIONS: The presence of other drugs did not appear to significantly alter the blood chlorpheniramine level, but no such correlation could be established with the hepatic value. The approximate 10-fold increase in the liver concentration was consistent with the general trend of drug distribution in the hepatic compartment. However, the contribution of postmortem redistribution of the drug to alter its concentration cannot be entirely ruled out. This study suggests that chlorpheniramine was present in some aviation fatalities at levels higher than therapeutic levels.

Accidents, Aviation↗
PubMed2004

Chlorpheniramine for motion sickness.

BACKGROUND: Motion sickness remains a significant problem for travelers and for those involved in naval, aviation and space operations. Many motion sickness remedies are also sedating, making them undesirable in many settings. METHODS: We studied chlorpheniramine as a potential motion sickness treatment. A placebo-controlled, double-blind, dose-ranging trial was performed to establish the most effective dose and the drug's effects on cognition. Eighteen normal, motion sickness susceptible subjects received placebo, low dose (4 mg) or high dose (12 mg) chlorpheniramine 3.5 hours before off-axis vertical rotation. Cognitive testing included a battery of objective and subjective tests performed before drug ingestion, at peak drug effect and following rotation. RESULTS: Chlorpheniramine significantly increased the time in the chair compared to placebo at high dose (7.2 minutes to 11.7 minutes) and low dose (7.2 minutes to 10.2 minutes). Chlorpheniramine did not affect performance on objective cognitive tests. Subjects reported significantly more sleepiness and less alertness with high-dose chlorpheniramine, although they could not reliably determine when they had received active drug. CONCLUSION: Chlorpheniramine is effective and could be considered for use against motion sickness. Chlorpheniramine also has the potential to be administered transdermally.

Adult↗
PubMed2000

Stereospecific versus nonstereospecific assessments for the bioequivalence of two formulations of racemic chlorpheniramine.

Chlorpheniramine (chlorphenamine, CPAM) is a racemic antihistaminic H1 drug containing two enantiomers. The aim of this study was to assess the bioequivalence of two formulations (reference and Vietnamese-tested formulation) of racemic chlorpheniramine combined with phenylpropanolamine in an open-labeled, randomized, crossover two-period study, after administration of 8 mg of racemic chlorpheniramine in 12 healthy Vietnamese subjects. First, dissolution of both formulations was tested in vitro according to USP requirements. Then the 12 subjects received both formulations after an overnight fast and a 7-day wash-out period. Plasma samples were collected up to 168 h. Plasma concentrations of total chlorpheniramine and its individual enantiomers were determined with a validated chiral HPLC method and pharmacokinetic parameters were estimated using model-independent analysis. For the reference formulation, Cmax and AUC values were higher for (+)S-chlorpheniramine ((+)S-CPAM) compared to (-)R-chlorpheniramine ((-)R-CPAM) (13.3 vs. 6.8 ng/ml and 409 vs. 222 ng/ml/h, respectively) while Clt/F and Vd/F were lower (9.8 vs. 17.6 l/h and 321 vs. 627 l, respectively). No difference was observed for Tmax, t(1/2), and MRT. Pharmacokinetic parameters were similar for the reference and the Vietnamese-tested formulation. Bioequivalence was assessed by Schuirmann test, as recommended by the current FDA and European Community criteria. Dissolution tests showed that both formulations were equivalent. A nonstereospecific, but not a stereospecific, approach indicated bioequivalence between the formulations.

Adult↗
PubMed2004

Simultaneous determination of chlorpheniramine and pseudoephedrine in human plasma by liquid chromatography-tandem mass spectrometry.

A sensitive and specific procedure for simultaneous quantitation of chlorpheniramine and pseudoephedrine in human plasma has been developed and validated. Analytes were extracted from plasma samples by liquid-liquid extraction, separated on a Diamonsil C18 column (250 x 4.6 mm i.d.) and detected by tandem mass spectrometry with an atmospheric pressure chemical ionization interface. Diphenhydramine was used as the internal standard. The method has a lower limit of quantitation of 0.2 and 2.0 ng/mL for chlorpheniramine and pseudoephedrine, respectively. The intra- and inter-day relative standard deviation, calculated from quality control (QC) samples were below 4.3% for chlorpheniramine and below 9.5% for pseudoephedrine. The inter-day relative error as determined from QC samples was within 4.7% for each analyte. The overall extraction recoveries of chlorpheniramine and pseudoephedrine were 77 and 61% on average, respectively. The method was successfully applied to pharmaockinetic study of chlorpheniramine and pseudoephedrine in volunteers receiving formulations containing 4 mg of chlorpheniramine maleate and 60 mg of pseudoephedrine hydrochloride.

Anti-Allergic Agents↗
PubMed1990

Psychomotor stimulant effects of the stereoisomers of chlorpheniramine.

The behavioral effects of the histamine H1 antagonists d- and l-chlorpheniramine and of the H2 antagonist zolantidine were determined in squirrel monkeys responding under a fixed-interval (FI) 3-min schedule of stimulus-shock termination. Although d-chlorpheniramine is known to be much more potent than l-chlorpheniramine for antagonizing H1 receptor-mediated effects of histamine or displacing [3H]-mepyramine from histamine H1 receptors, similar doses of racemic chlorpheniramine and the d- and l-isomers (3.0-10.0 mg/kg) produced comparable increases in rates of responding. Zolantidine (1.0-17.0 mg/kg) did not alter or, at the highest dose, markedly decreased responding. These findings suggest that the psychomotor stimulant effects of chlorpheniramine involve actions other than the blockade of histamine H1 or H2 receptors. Selected H1 antagonists and cocaine are known to have comparable rate-increasing, reinforcing, and discriminative stimulus effects and, recently, the enantiomers of chlorpheniramine have been shown to displace [3H]-cocaine from binding sites in CNS with approximately equal potency. Possibly, such actions mediate behavioral effects common to H1 antagonists and cocaine.

Animals↗
PubMed1985

The development of subsensitivity to chlorpheniramine.

To assess the development of subsensitivity to antihistamines, titrated prick skin test (PSTs) were performed to seven fivefold dilutions of histamine and either morphine or antigen at specific intervals during therapy. Ten subjects received chlorpheniramine, 24 mg per day, and placebo in a double-blind crossover study. Total wheal area was measured at baseline and after 1, 3, 7, 21, and 24 days. The dose of chlorpheniramine (or placebo) was doubled from days 22 to 24 to assess the response to dosage increase. Serum levels of chlorpheniramine were measured at days 3 and 21 in six patients. Maximal skin test suppression was observed on days 3 or 7. On day 21 there was significantly less (p less than 0.01) suppression of all PSTs than on days 3 or 7. Mean serum chlorpheniramine was 48.7 ng/ml on day 3 and 36.1 ng/ml on day 21 (not significant). There was no significant correlation between changes in serum chlorpheniramine levels and changes in PST suppression. Doubling the dose of chlorpheniramine did not achieve the maximal suppression observed at days 3 or 7. We conclude that subsensitivity to antihistamines develops between 7 and 21 days of therapy and cannot be completely overcome by doubling the dose. The decreased effect does not appear to be due to induced metabolism but may be related to increased H1 receptor number.

Adolescent↗
PubMed1994

Benefit/risk ratio of the antihistamines (H1-receptor antagonists) terfenadine and chlorpheniramine in children.

There are few objective studies of the benefit/risk ratio of H1-receptor antagonists in children. We hypothesized that terfenadine would provide as effective peripheral H1 blockade as chlorpheniramine in young patients, but would cause less central nervous system dysfunction. We tested this hypothesis with epicutaneous histamine tests to monitor peripheral H1 blockade, P300-event-related potentials as a measure of cognitive processing, and a visual analog scale for somnolence, in a double-blind, single-dose, placebo-controlled, three-way crossover study in 15 children with allergic rhinitis (mean age, 8.5 +/- 1.4 years). On 3 different days the children received terfenadine, 60 mg, chlorpheniramine, 4 mg, or placebo; the tests were performed before and 2 to 2 1/2 hours after dosing. Both terfenadine and chlorpheniramine suppressed the histamine-induced wheal and flare compared with baseline and with placebo; terfenadine was significantly more effective (p < 0.05). Terfenadine did not increase the latency of P300-event-related potentials at the parietal (Pz) or frontal (Fz) scalp electrodes compared with baseline, in contrast to chlorpheniramine and placebo, which did increase P300 latency. Terfenadine and placebo did not increase somnolence compared with baseline, but chlorpheniramine did. In children, as previously documented in adults, terfenadine has a more favorable benefit/risk ratio than chlorpheniramine, as shown by production of significantly greater peripheral histamine blockade and significantly less central nervous system dysfunction.

Action Potentials↗
PubMed1998

The H1- and H2-histamine blockers chlorpheniramine and ranitidine applied to the nucleus basalis magnocellularis region modulate anxiety and reinforcement related processes.

This study examined the effects of the H1-antagonist chlorpheniramine and the H2-antagonist ranitidine on reinforcement and anxiety-parameters following unilateral injection into the vicinity of the nucleus basalis magnocellularis (NBM). In Experiment 1, rats with chronically implanted cannulae were injected with chlorpheniramine or ranitidine (each at doses of 0.1, 1, 10 and 20 microg) and were placed into one of four restricted quadrants of a circular open field (closed corral) for a single conditioning trial. During the test for conditioned corral preference, when provided a choice between the four quadrants, only those rats injected with 10 or 20 microg chlorpheniramine spent more time in the treatment corral, indicative of a positively reinforcing action. None of the other doses of chlorpheniramine or of the H2-antagonist influenced rats' preference behavior. In Experiment 2, the elevated plus-maze (EPM) was used to gauge possible anxiolytic or anxiogenic effects of intra-basalis injection of chlorpheniramine or ranitidine (each at doses of 0.1, 1, 10 and 20 microg). A single injection of chlorpheniramine at 0.1 or 20 microg as well as ranitidine at 20 microg was found to exert anxiolytic-like effects in the EPM. Both compounds elevated the time spent on the open arms and increased scanning over the edge of an open arm. None of the other doses of the H1- and H2-antagonist influenced rats' behavior in the EPM. In sum, these findings show that H1- and H2-receptor antagonists differentially modulate reinforcement and fear-related processes in the NBM and thus, provide the first evidence for a behavioral relevance for the histaminergic innervation of this brain site.

Animals↗
PubMed1997

The histamine H1-antagonist chlorpheniramine facilitates learning in aged rats.

The effect of the histamine H1-receptor antagonist chlorpheniramine on inhibitory avoidance conditioning was investigated in 31-month-old rats, using a one-trial step-through avoidance task. Immediately after the learning trial, old rats were injected intraperitoneally with 5 or 10 mg/kg d-chlorpheniramine. Control groups included vehicle-injected old and adult (4-month-old) rats and a group of aged animals given an injection of 10 mg/kg chlorpheniramine 5 h after the training trial. When tested 24 h after training, aged rats receiving 10 mg/kg chlorpheniramine exhibited longer step-through latencies than vehicle-treated old controls, indicative of superior learning of the task. The hypermnestic effects of 10 mg/kg chlorpheniramine were no longer evident when injection was performed 5 h, rather than immediately after the learning trial, ruling out enduring proactive effects of the treatment on test performance. Furthermore, vehicle-treated old rats showed poorer inhibitory avoidance performance than vehicle-treated adult controls. Thus, the improvement in performance after the 10 mg/kg dose of chlorpheniramine can be interpreted in terms of a compensation of performance deficits in the old rats.

Aging↗
PubMed1998

Stereoselective pharmacokinetics of chlorpheniramine and the effect of ranitidine.

This single-dose, randomized, crossover study was carried out to investigate the potential effect of ranitidine on the pharmacokinetics of chlorpheniramine. The study also afforded an opportunity to add to the limited data currently available on the stereoselective pharmacokinetics of chlorpheniramine. Healthy subjects received a single oral 4 mg dose of racemic chlorpheniramine on two separate occasions: alone, and on day 6 of dosing with ranitidine 75 mg b.i.d. for 8 days. Serum concentrations and urinary recovery of (S)-(+)- and (R)-(-)-chlorpheniramine were unaffected by administration of ranitidine, indicating no pharmacokinetic drug-drug interaction. The observed chlorpheniramine pharmacokinetic data were consistent with previous data and indicated approximately 2.5-fold higher serum concentrations of the (S)-(+) enantiomer. Previously reported high variability in chlorpheniramine pharmacokinetics was greatly reduced by well-controlled food and fluid intake.

Adolescent↗
PubMed1998

Effect of the H1 blocker d-chlorpheniramine on cerebral blood flow in the conscious dog during normocapnic hypoxia.

The mechanism causing cerebral vasodilatation during hypoxia remains unclear. A role for histamine is suspected because H2 receptor-blocking drugs blunt the hypoxia-induced increase in cerebral blood flow (CBF). Moreover, in vitro blockade of H1 receptors by chlorpheniramine decreases the vasodilatation of cerebral arteries that is induced by histamine. The present study tested the hypothesis that an H1 receptor blocker (d-chlorpheniramine) would have a similar effect in vivo during hypoxia. Isocapnic hypoxia (inspired oxygen fraction, FIO2 = 0.10; inspired carbon dioxide fraction, FICO2 = 0.035) was induced in 16 conscious dogs randomly divided into two groups: eight dogs received saline intravenously (controls) at time 0 (normoxia) and after 2 h and 4 h hypoxia, and the other eight dogs received d-chlorpheniramine intravenously (0.5 mg kg-1) to block the H1 receptors. Regional CBF was measured by the radioactive microspheres technique 15 min after each injection of d-chlorpheniramine or saline. In the control group, CBF increased during hypoxia in all regions of the brain. In the d-chlorpheniramine group, total CBF increased similarly after 2 h of hypoxia. After 4 h of hypoxia, the increase was limited, especially in the pons, cerebral peduncles, hippocampus, hypothalamus, thalamus, and occipital lobes (six out of 12 studied regions). It is concluded that the H1 blocker d-chlorpheniramine did not strongly inhibit the increase in CBF during hypoxia. After cumulative doses, however, as in the fourth hour of hypoxia, the increase in total CBF was limited.

Animals↗
PubMed2001

The H1-receptor antagonist dextro-chlorpheniramine impairs selective auditory attention in the absence of subjective awareness of this impairment.

Although previous studies have shown that the human attention system is partially affected by chlorpheniramine, the effects of chlorpheniramine on human auditory selective attention have not yet been explored. This study examines the effects of a single dose of 4 mg of dextro-chlorpheniramine on human auditory selective attention by means of the evaluation of the event-related brain potential (ERP) processing negativity (PN). The study sample consisted of 20 healthy male humans, who received either a single 4-mg dose of dextro-chlorpheniramine or a placebo in a double-blind design. The subjects were given a dichotic listening task, in which they were instructed to press a response button upon detecting deviant tones (target) while their ERPs were recorded. In parallel, subjective tests evaluated the daytime sleepiness, overall vigor, and affect of the subjects. Results showed that the auditory selective attention is impaired under the effects of chlorpheniramine, as reflected by an attenuation of PN amplitude and by a decrease of performance in the group of subjects who took a single 4-mg dose of dextro-chlorpheniramine. No subjective change in the daytime sleepiness, overall vigor, or affect of the subjects was observed. This lack of conscious awareness of the side effects may lead to situations of risk in tasks for which auditory information is important, because no subjective indicators of attention impairment are available to the subjects.

Adult↗
PubMed2003

The anti-allergic effects of a cromolyn sodium-chlorpheniramine combination compared to ketotifen in the conjunctival allergen challenge model.

PURPOSE: To compare the inhibitory effects of a topical combination product, cromolyn sodium (DSCG) 4% with the antihistamine, chlorpheniramine, with those of topical ketotifen 0.05% on the clinical allergic reaction induced by the conjunctival allergen challenge (CAC). METHODS: Ten allergic but non-active patients were challenged in both eyes with increasing doses of specific allergen to obtain a positive bilateral reaction (visit 1). They were then rechallenged after 1 week to confirm the allergic threshold dose response (visit 2). After 2 weeks, a third CAC was performed bilaterally 30 minutes after topical application of DSCG-chlorpheniramine in one eye and ketotifen in the contralateral eye in a double-masked fashion (visit 3). Clinical signs and symptoms were registered 5, 10, 15, and 20 minutes after challenge using the standard scoring system. Tear cytology was performed 30 minutes after challenge. RESULTS: Comparing the two drug effects at visit 3, DSCG-chlorpheniramine was shown to be superior to ketotifen at all time points for itching (p < 0.01) and at 5 minutes for redness (p < 0.01). For the total signs score, DSCG-chlorpheniramine was shown to be superior to ketotifen at all time points (p < 0.01), and at 10 and 15 minutes for the total symptoms score (p < 0.05). Compared to visit 2, DSCG-chlorpheniramine significantly lowered itching (p < 0.001) and redness (p < 0.05) at 5, 10, 15, and 20 minutes after challenge. Ketotifen significantly lowered itching at 5 and 10 minutes (p < 0.001) and redness at 5, 10, and 15 minutes (p < 0.05). Both drugs reduced the total number of cells evaluated by tear cytology during the early-phase reaction (p < 0.05). CONCLUSIONS: DSCG-chlorpheniramine was found to be more effective than ketotifen at preventing itching and redness in the CAC model.

Administration, Topical↗
PubMed2000

Evidence for the degradation of maleate moiety in chlorpheniramine maleate solution using a stability-indicating HPLC method.

The degradation phenomenon of maleate moiety of chlorpheniramine maleate in solution has been demonstrated by means of a peculiar ion-pair HPLC method developed by the authors, which permits the simultaneous determination of chlorpheniramine and maleate. A commercial cough drug containing chlorpheniramine maleate was dissolved in water with m-hydroxybenzoic acid as an internal standard, and then kept for several days at room temperature. It was recognized that the maleate content in the drug solution had gradually decreased, whereas chlorpheniramine content had not decreased. A simple solution of maleic acid was also kept for several days at room temperature, and it was also recognized that the maleate content in the solution preserved at the same concentration as the solution of the commercial cough drug had gradually decreased, and the percent of remaining maleate reached zero. The degraded peaks on HPLC chromatogram were not detected at all by UV detector, and the disappearance of maleate was ascertained by GC-MS. No detectable example of maleate of chlorpheniramine maleate in a commercial cough syrup has suggested that maleate moiety of chlorpheniramine maleate decomposed to carbon dioxide.

Chlorpheniramine↗
PubMed1992

Enantioselective N-oxygenation of chlorpheniramine by the flavin-containing monooxygenase from hog liver.

1. The metabolism of racemic, (D)- and (L)-chlorpheniramine, a widely used antihistamine, was studied in microsomes and with highly purified flavin-containing monooxygenase from hog liver. 2. Although some N-demethylation was observed, the major metabolite of chlorpheniramine in hog liver microsomes was the aliphatic nitrogen N-oxide. Chlorpheniramine was extensively N-oxygenated by the highly purified flavin-containing monooxygenase from hog liver. 3. N-Oxygenation of chlorpheniramine in both microsomes and highly purified flavin-containing monooxygenase from hog liver was enantioselective. The Km for (D)-chlorpheniramine N-oxygenation was markedly lower than that for (L)-chlorpheniramine. 4. Molecular modelling studies were performed to investigate the nature of the substrate binding region.

Animals↗
PubMed2004

To evaluate and compare the effects of first generation anti-histamine (chlorpheniramine maleate) and second generation anti-histamine (loratadine) on isolated trachea of rabbit.

OBJECTIVE: The incidence of respiratory allergy has increased gradually over the past several years and current estimates suggest that allergic rhinitis affects approximately 20% of the population. Large scales population surveys indicate that up to 38% of patients with rhinitis have asthma. The allergic response in the airways is an important pathogensis to cause bronchoconstriction owing to increased responsiveness of tracheo bronchial tree to various stimuli and also causes the release of histamine and other chemical mediators from mast cells. Histamine has been shown to be an important mediator of an allergic reaction in both the upper and lower respiratory airways. Chlorpheniramine maleate is a stable, most potent, sedative first generation anti-histamine and is effective in the treatment of allergic disorders. Loratadine is a highly potent, non-sedating, long acting tricyclic, second generation anti-histamine. It is indicated in allergic rhinits, chronic idiopathic urticaria and allergic bronchial asthma. The purpose of study was to evaluate the antagonistic effects of chlorpheniramine maleate and loratadine on histamine induced contractions in isolated trachea of rabbit and also to compare the effects of first generation anti-histamine (chlorpheniramine maleate and second generation anti-histamine loratadine). METHODS: In this study twenty-four experiments were performed on isolated trachea of rabbit, in the presence of selected standard concentration of histamine dihydrochloride, antagonistic effects of various concentrations of chlorpheniramine maleate (10-18 to 10(-3) gm/ml) and loratadine from concentrations 10(-18) to 10(-3) gm/ml were recorded by Polygraph Model 7B in terms of rate and amplitude. RESULTS: Chlorpheniramine maleate showed non-significant antagonistic effect from concentrations 10(-18) to 10(-3) gm/ml in case of rate and 10(-18) to 10(-8) gm/ml in case of amplitude. Significant response showed from concentrations 10(-8) to 10(-3) gm/ml in case of rate (P<0.001) and 10(-7) to 10(-3) gm/ml in case of amplitude (P<0.001) while, loratadine showed non-significant response from concentrations 10(-18) to 10(-12) gm/ml in case of rate and from concentration 10(-18) to 10(-14) gm/ml in case of amplitude. Significant response observed from concentrations 10(-11) to 10(-3) gm/ml in case of rate and 10(-13) to 10(-3) gm/ml in case of amplitude. CONCLUSION: It was concluded that chlorpheniramine maleate antagonized the histamine induced contractions 80.65% at concentration 10(-3) gm/ml in case of amplitude and 11.35% at concentration 10(-3) gm/ml in case of rate and loratadine 76.82% in case of amplitude and 10.59% in case of rate.

Animals↗