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The pharmacokinetics and bioavailability of clemastine and phenylpropanolamine in single-component and combination formulations.

Studies were conducted in healthy male volunteers (n = 171; age range, 19-49 years; 22-27 subjects per study) to examine the following: pharmacokinetics and dose proportionality of the antihistamine clemastine; the effect of coadministration of phenylpropanolamine and clemastine on the pharmacokinetics of the two drugs; and the bioavailability of clemastine tablets and combination tablets of clemastine and sustained-release phenyl-propanolamine under fasted and fed conditions after single-dose administration and at steady state. All studies used crossover designs, with randomized drug treatments separated by a 7-day washout period for the single-dose studies, and with administration every 6 or 12 hours for 7 days per treatment for the steady-state studies. After single oral doses of clemastine solution (1,2, and 4 mg), the area under the concentration-time curve (AUC) and maximum concentration (Cmax) were dose proportional. Clemastine showed a first-pass reduction in the extent of absorption, with oral bioavailability calculated as 39.2 +/- 12.4%. Extravascular distribution of drug was suggested by the high volume of distribution (799 +/- 315 L) and low Cmax (0.577 +/- 0.252 ng/mL/mg) observed at 4.77 +/- 2.26 hours after administration, and by the biphasic decline in plasma concentration. The terminal elimination half-life (t1/2) of clemastine was 21.3 +/- 11.6 hours. Steady-state concentrations of clemastine were consistent with linear pharmacokinetic processes, and clearance was unaffected by age in the range studied, or by race. Clemastine solution and tablets were bioequivalent, and food had no significant effect on rate and extent of absorption of clemastine. The 1- and 2-mg clemastine tablets showed proportional bioavailability. Coadministration of clemastine with phenylpropanolamine did not significantly influence the pharmacokinetics of clemastine or the AUC and elimination t1/2 of phenylpropanolamine, but reduced the rate of absorption of phenylpropanolamine. Combination tablets containing 1 mg or 2 mg of immediate-release clemastine plus 75 mg of sustained-release phenylpropanolamine for twice daily administration were bioequivalent to the separate components and showed no significant interaction with food.

Adult↗

Low dose clemastine inhibits sneezing and rhinorrhea during the early nasal allergic reaction.

BACKGROUND: Clemastine (1 mg) is currently available over-the-counter for the treatment of allergic rhinitis. OBJECTIVE: To evaluate the efficacy of half the standard dose of clemastine (0.5 mg) in inhibiting the nasal response to allergen and the cutaneous response to histamine. METHODS: Double-blind, placebo-controlled, crossover study of 20 allergic subjects out of season. The subjects received placebo or clemastine administered one, four, and six hours before the challenges. Filter paper discs were used both to challenge the nasal mucosa with diluent and allergen and collect generated secretions. Sneezes, secretion weights, nasal and ocular symptoms, and albumin levels in nasal secretions were monitored for the nasal challenge. Intradermal skin testing was performed with diluent followed by histamine and the wheal and flare reactions were measured. RESULTS: There was a significant reduction in the number of sneezes after clemastine administered one, four, and six hours prior to challenge compared with placebo (P < .01). Clemastine administered four and six hours before challenge reduced sneezing significantly more than clemastine administered one hour before challenge (P < .05). Antigen-induced increases in secretion weights and symptoms of rhinorrhea were significantly reduced compared with placebo only when clemastine was administered four and six hours prior to challenge (P < .05). Pretreatment with clemastine had no significant inhibitory effects on other nasal symptoms or on albumin levels in nasal secretions, an objective index of increased vascular permeability. Pretreatment with clemastine did not inhibit the histamine-induced wheal skin reaction but showed a tendency, when administered six hours prior to the intradermal challenge, to reduce the flare reaction induced by the lowest dose of histamine (P = .05). CONCLUSIONS: The data show that clemastine, given at half the usual dose four and six hours prior to allergen challenge, provides relief for sneezing and rhinorrhea and suggests that this dose might be useful in the treatment of allergic rhinitis.

Adult↗

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

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

Animals↗

Administration of clemastine--H1 histamine receptor blocker in the prevention of haemodynamic disorders after protamine sulfate administration in patients subjected to coronary artery bypass grafting in extracorporeal circulation.

INTRODUCTION: Adverse effects of protamine administration after CPB: fall in arterial blood pressure and pulmonary hypertension are still a source of problems. CPB and protamine administration are both accompanied by increased histamine levels in blood. The aim of this study was to examine if clemastine can accelerate the normalisation of arterial blood pressure during the protamine administration after CPB during CABG operations. MATERIAL AND METHODS: Fifty three patients subjected to CABG operations were studied. Control group (n = 27) did not receive clemastine, Clemastine group (n = 26) received 2 mg i.v. clemastine, before CPB. After CPB were completed, patients were given protamine (heparin to protamine ratio--1:1.5) within 7 minutes, through peripheral vein. Changes in arterial blood pressure from the beginning of protamine administration to 2.5, 5, 7.5, 10, 15, and 30 minutes thereafter, as well as heart rate, CVP, doses of inotropic drugs and vasodilators were compared between the groups. RESULTS: No difference in heart rate, CVP, doses of inotropic drugs and vasodilators between the group was noted. An increase in arterial blood pressure 5, 7.5, 10, and 15 minutes after the beginning of the protamine administration were greater in clemastine group than in control group. Groups were comparable with regard to surgical procedures and doses of anaesthetic drugs. It is now known that protamine exerts a negative effect on cardiac contractility either through a decrease in coronary perfusion pressure (vasodilatation), or through a direct toxic effect on cardiac muscle. The administration of clemastine before CPB can reduce peripheral vasodilatation and capillary leak related to histamine release during CPB. In the clemastine group, faster increase in arterial blood pressure toward a physiologic range was observed. We conclude that administration of clemastine is connected with the normalization of ABP during and after protamine reversal of heparin coagulation during CABG operations.

Blood Pressure↗

A multicentre study of loratadine, clemastine and placebo in patients with perennial allergic rhinitis.

This multicentre, double-blind, randomized parallel-group study compared 3 weeks' treatment with either loratadine (Clarityn) 10 mg once daily, or clemastine (Tavegyl) 1 mg twice daily, and placebo in outpatients with active perennial allergic rhinitis. 155 patients were evaluated for efficacy and safety. Grading of four nasal and three non-nasal symptoms, rhinoscopy signs, and therapeutic response was performed on treatment days 6, 13, and 20. Patients recorded daily symptoms and possible adverse experiences in a diary, also indicating when symptoms of active rhinitis were relieved. Loratadine and clemastine were statistically significantly superior to placebo throughout the study (P less than 0.05), based on assessment of patients' nasal and eye symptoms, patients' diary scores, rhinoscopy signs of symptoms, and onset of relief. The loratadine group showed a statistically significantly (P less than 0.05) faster onset of relief of symptoms compared with the group treated with clemastine. Concerning nasal stuffiness, loratadine was significantly (P less than 0.05) superior to clemastine after 1 week's treatment. Reports of adverse reactions showed that significantly (P less than 0.05) more patients complained of sedation in the clemastine than in the loratadine group. Regarding other adverse experiences and laboratory tests, the three treatment groups were statistically comparable (P less than 0.05). The study showed that compared with placebo both loratadine and clemastine were effective in relieving nasal and eye symptoms in patients with perennial allergic rhinitis. Loratadine was safe and well tolerated and was significantly less sedative than clemastine; loratadine may therefore possess an advantage in clinical use in the treatment of perennial allergic rhinitis.

Adolescent↗

Effect of an inhaled antihistamine (clemastine) as a bronchodilator and as a maintenance treatment in asthma.

Although intravenous chlorpheniramine can cause bronchodilatation, oral and parenteral antihistamines have not proved useful in treating asthma. Inhaled antihistamines may cause throat irritation, but a recent study of the antihistamine, clemastine, showed it to be an effective bronchodilator without irritant effects. We have extended these studies to determine the site of action of inhaled clemastine and to assess its potential usefulness both as a bronchodilator and as a maintenance treatment. Eleven stable asthmatic patients received inhaled clemastine and placebo and the effect was assessed by serial maximum expiratory flow volume (MEFV) curves breathing air and a helium/oxygen (He/O2) mixture. There was no significant improvement in peak flow rates during air breathing after clemastine and no significant difference between the responses to drug and placebo. Minor but significant changes were seen in some flow measurements on the downslope of the MEFV curve during air and He/O2 breathing, and these are tentatively ascribed to a dilating effect of clemastine on peripheral airways where flow is laminar. Subsequent administration of inhaled isoprenaline showed the patients to be still capable of significant bronchodilatation. The addition of clemastine, from a pressurised aerosol, to the patients' therapeutic regimen for two weeks was no more effective than placebo in controlling airflow obstruction, and did not reduce the need for standard bronchodilators. In our patients clemastine was not a clinically useful bronchodilator either acutely or as a maintenance treatment for asthma.

Adult↗

Determination of clemastine in human plasma by gas chromatography with nitrogen-phosphorus detection.

A method for the quantitative determination of clemastine in human plasma has been developed and validated. The assay uses gas chromatography with nitrogen-phosphorus detection and a HP-1 capillary column (25 mx0.22 mm, film thickness 0.33 mm) coated with dimethylpolysiloxane. Clemastine (with orphenadrine as internal standard) was isolated from human plasma using liquid-liquid extraction. A linear relationship was observed between 0.1 and 12.8 ng/ml using the peak area ratio of clemastine to orphenadrine with a correlation coefficient greater than 0.99 (the detection limit for clemastine was 0.06 ng/ml). The intra- and inter-day coefficients of variation were less than 11%. The developed method was used for the analysis of plasma samples from healthy volunteers (n = 19) to examine the pharmacokinetics of the antihistamine clemastine after single and multiple oral doses of clemastine fumarate.

Adult↗

Inhaled clemastine, an H1 antihistamine inhibits airway narrowing caused by aerosols of non-isotonic saline.

Asthmatic subjects were challenged with aerosols of hyper- and hypotonic saline 15 min (Group A) and 90 min (Group B) after inhaling clemastine. Measurements were made of forced expiratory volume in one second (FEV1) before and after medication and after challenge. When the FEV1 values (% predicted) were compared on the active and placebo days they were higher 15 min after clemastine (p less than 0.05) for both challenges and higher 90 min after clemastine inhalation (p less than 0.05) for the hypertonic challenge. The % fall in FEV1 was compared after the same concentration of saline aerosol had been given on both active and placebo days. In Group A the % fall in FEV1 on the clemastine day was reduced after challenge with hypertonic (p less than 0.02) and hypotonic (p less than 0.03) aerosol. In Group B there was a reduction in the % fall in FEV1 on the clemastine day only after hypertonic challenge (p less than 0.04). The protective effect afforded by clemastine was unrelated to change in baseline lung function. We conclude that histamine is an important mediator of the airway response to non-isotonic aerosols and suggest that the aerosol route of administration may be useful for delivering antihistamines.

Administration, Inhalation↗

Double-blind, controlled study of clemastine fumarate, chlorpheniramine and placebo in patients with seasonal allergic rhinitis.

A whole body plethysmograph (body box) equipped with a flow meter (see Figure 1) was used for objective quantification of the effects of single doses of clemastine fumarate 2.68 mg, chlorpheniramine 4 mg and placebo in a double-blind study of 48 patients with seasonal allergic rhinitis. This technique offers an objective means of assessing drug effects on nasal congestion and obstruction. Before the development of whole body plethysmography, only subjective assessments of antihistamines' effects on nasal blockage or congestion were available. These subjective reports usually noted that nasal blockage or congestion was refractory to antihistamines or minimally relieved by them. However, in this study, nasal and oral airway resistances, each measured by whole body plethysmography, were lowered by clemastine fumarate and chlorpheniramine. These results were corroborated by the patients' and physician's assessments of changes in symptom severity and the physician's evaluation of intranasal photographs taken for each patient. Oral airway resistance of patients treated with clemastine fumarate was improved to a significantly greater extent than in patients receiving placebo. At two hours post-drug, patients receiving clemastine fumarate usually showed a greater response in most assessments than those receiving chlorpheniramine, and the trend of most comparisons was clearly in favor of clemastine fumarate. Patients in all three treatment groups experienced drowsiness but both incidence and severity were lower with clemastine fumarate.

Airway Resistance↗

Effectiveness of clemastine fumarate for treatment of rhinorrhea and sneezing associated with the common cold.

Limited data support the use of first-generation antihistamines for treatment of the common cold. The purpose of this study was to test the effectiveness of clemastine fumarate, a first-generation antihistamine, for treatment of sneezing and rhinorrhea associated with naturally occurring common colds. Four hundred three subjects (202 clemastine fumarate recipients and 201 placebo recipients) who reported new onset (< 24 hours) of cold symptoms that included rhinorrhea or sneezing were studied. At baseline (day 1), the mean symptom-severity scores +/- SEM for the clemastine fumarate and placebo groups were not significantly different. The mean rhinorrhea-severity score +/- SEM was not different on day 2; however, on day 3, the mean rhinorrhea-severity score +/- SEM was 1.02 +/- 0.07 for the clemastine fumarate group and 1.39 +/- 0.07 for the placebo group (P < .001). This treatment effect persisted on day 4. A significant effect on sneezing was noted on days 2-4. Sedation occurred in 14% of the clemastine fumarate-treated subjects and 1.5% of the placebo-treated subjects (P < .0001).

Adolescent↗

A comparison of ketotifen with clemastine, ipratropium bromide and sodium cromoglycate in exercise-induced asthma.

Exercise-induced asthma (EIA) was provoked by a standardized treadmill running for 8 min in seven atopic adult asthmatics. The tests were performed using a double-dummy technique after placebo, oral ketotifen, inhaled clemastine, ipratropium bromide and sodium cromoglycate (SCG), in a random single blind-fashion on different days. The mean post-exercise percentage fall in forced expiratory volume in 1 sec (FEV1) was 47 (s.e. 6.95), 39 (s.e. 8.35), 27 (s.e. 7.17), 23 (s.e. 7.69) and 7.0 (s.e. 4.62)% respectively. There was significantly less mean bronchoconstriction with SCG (P less than 0.01), ipratropium bromide and clemastine (P less than 0.05) but not with ketotifen. Six out of seven individual patients had significant protection of EIA with sodium cromoglycate, four with ipratropium bromide, three with clemastine but only one with ketotifen. Ipratropium bromide and clemastine were bronchodilators at rest, whereas SCG and ketotifen were not. Despite its claims to work as a mast cell stabilizing drug, ketotifen in a single dose does not have an effect similar to sodium cromoglycate in EIA, nor does it compare with inhaled clemastine or ipratropium bromide.

Adolescent↗

Comparative study of the efficacy and tolerance of terfenadine and clemastine in patients with seasonal allergic rhinitis.

The efficacy and tolerance of alpha-[4-(1,1-dimethylethyl)phenyl]-4-(hydroxyphenylmethyl)-1- piperidinebutanol (terfenadine, RMI 9918, Triludan, Teldane, resp.) and clemastine were investigated in 20 patients in a single blind, randomized clinical study of three months duration. A total of 15 patients was treated with terfenadine (2 X 60 mg/day), and five patients were treated with clemastine (2 X 1 mg/day). Clemastine and terfenadine were applied as a prophylaxis against seasonal allergic rhinitis. No change in body function or in laboratory values (heart rate, respiratory rate, body temperature, and blood pressure) was seen after antihistamine treatment. Two patients taking clemastine reported moderate sedation. No sedative effects were reported in the terfenadine group. Two patients in the clemastine group and one patient in the terfenadine group had an attack of allergic rhinitis during the study. In this study terfenadine showed good efficacy and tolerance similar to that reported by former clinical studies. It should be emphasized that sedation was not observed with terfenadine.

Adolescent↗

A comparison of triprolidine and clemastine on histamine antagonism and performance tests in man: implications for the mechanism of drug induced drowsiness.

The effects of triprolidine hydrochloride 1.25, 2.5 and 5 mg, clemastine 1 and 2 mg and lactose dummy administered orally, in a balanced order, at weekly intervals to 12 healthy volunteers, on the flare and weal responses to intradermal histamine injection, and also on both subjective effects and objective psychomotor tests were examined. The histamine response was significantly larger at 09.00 h falling through the day but increasing by late afternoon. Triprolidine produced a dose-related antagonism of both flare and weal response maximal at 3 h and wearing off after the lower doses at 8 h. Clemastine by contrast produced poor antagonism of histamine at 3 h but a marked effect at 5.5 and 8 h. Auditory vigilance was significantly (p less than 0.05) impaired by all doses of triprolidine 1 to 2 h after administration, but no change followed clemastine at this time. When tested 6 to 7 h after administration significant impairment followed both doses of clemastine but only the 5 mg dose of triprolidine. Both drugs prolonged reaction time in a dose-related manner at 2.5 and 5.0 h but the effects had worn off at 7 h. Digit symbol substitution was impaired by the top doses of both antihistamines but short term memory was unaffected. Subjective effects measured using analogue lines reflected the effects in the vigilance test, in that drowsiness and mental impairment were noted early after triprolidine, while clemastine produced maximal effects at 5 h. Subjects were ranked in order of magnitude of inhibition of both flare and weal, and impairment of vigilance, prolongation of reaction time and subjective drowsiness score. There was no indication of a significant correlation, using Spearman's test, between antagonism of histamine and effects on the central nervous system.

Adult↗

Placebo controlled comparison of acute effects of ebastine and clemastine on performance and EEG.

The effects of single oral doses of 10 and 20 mg ebastine were compared with placebo and 2 mg clemastine in a double-blind cross-over study in 16 healthy male volunteers. Clemastine produced the known pattern of changes, namely impairment of psychomotor performance, drowsiness, and a selective effect on cognitive processes. Earlier encoding in a perceptual stage was slowed whereas abstract classification processes were not affected. Electrophysiological measures of vigilance showed a general decrease in vigilance especially 2.5 and 4.5 h after dosing. In contrast at no time was any effect of ebastine different from that of the placebo. Ebastine 10 and 20 mg differed positively from clemastine in its effect on pursuit tracking, subjective rating of drowsiness and general discomfort. Ebastine 10 mg also differed positively from clemastine in the EEG features of vigilance. It is concluded that 10 and 20 mg ebastine were free from sedative adverse effects.

Adult↗

A comparison of the effects of ketotifen and clemastine on cutaneous and airway reactivity to histamine and allergen in atopic asthmatic subjects.

We compared the effects of ketotifen, a drug with antihistaminic and antianaphylactic properties, with those of clemastine, a conventional H1 antihistamine, on cutaneous and airway reactions to histamine and allergen in atopic asthmatic subjects. Eight subjects received ketotifen, and seven subjects received clemastine, 1 mg twice daily, for two periods of 3 wk. A 2-week interval separated the periods of medication. Maximum expiratory flow rates were measured before and after each treatment period and did not change significantly. Bronchial provocation testing to histamine was performed before and after the first period of medication, and the provocative concentration of histamine required to reduce the forced expiratory volume in 1 sec by 20% from control was increased 4.9-fold by ketotifen (p less than 0.02) and 6.5-fold by clemastine (p less than 0.01). Quantitative histamine and allergen skin testing performed before and after the second period of medication demonstrated significant attenuation of the cutaneous reactions by both medications. Neither medication, however, afforded significant protection against inhaled allergen. Our results suggest that, in the doses used, ketotifen has antihistaminic actions in man equivalent in potency to clemastine but does not appear to have significant additional effects on immediate skin or bronchial responses to allergen.

Adult↗

The effect of ranitidine, alone and in combination with clemastine, on allergen-induced cutaneous wheal-and-flare reactions in human skin.

The effect of intradermal ranitidine (administered alone and in combination with clemastine) on allergen-mediated wheal-and-flare reactions has been evaluated in a double-blind study on 10 healthy atopic volunteers. Ranitidine alone, administered in doses over a 10(4)-fold concentration range, had no effect on the size either of allergen-induced wheal or flare reactions. Clemastine alone evoked a dose-related inhibition of both wheal and flare. Compared to the inhibition achieved by clemastine alone, the combination of ranitidine with clemastine produced a small but significant increase in inhibition of allergen-induced flare at ranitidine concentrations of 10(-5) mol/L (p less than 0.001) and 10(-6) mol/L (p less than 0.01), and of allergen-induced wheal at ranitidine concentration 10(-5) mol/L (p less than 0.01). Our results provide further evidence for the presence of cutaneous histamine H2 receptors and their participation in the formation of allergen-mediated skin reactions but indicate that the contribution of cutaneous histamine H2-receptor stimulation to the production of immediate wheal-and-flare reactions evoked by allergen is only modest.

Adolescent↗

High-performance liquid chromatographic-tandem mass spectrometric method for the determination of clemastine in human plasma.

A highly sensitive high-performance liquid chromatographic-tandem mass spectrometric method (HPLC-MS-MS) has been developed to quantitate clemastine in human plasma for the purpose of pharmacokinetic studies. Sample preparation was carried out by liquid-liquid extraction using deuterated clemastine as an internal standard. Chromatographic separation used a C18 reversed phase polymer column giving an extremely fast total run time of 2 min. The method was validated and used for the bioequivalence study of clemastine tablets in healthy male volunteers (n=28). The lower limit of detection proved to be 0.01 ng/ml for clemastine.

Chromatography, High Pressure Liquid↗

Randomized controlled trial of clemastine fumarate for treatment of experimental rhinovirus colds.

We used a rhinovirus challenge model to test the therapeutic efficacy of clemastine fumarate for reducing sneezing and nasal secretion in a double-blind, randomized clinical trial. Clemastine fumarate (1.34 mg) or placebo was administered at 8 A.M. and 8 P.M. for 4 days, beginning 24 hours, 36 hours, 48 hours, and 60 hours after viral challenge. Infected evaluable subjects who received clemastine (n = 75) had reduced sneeze-severity scores compared with those who received placebo (n = 75) on illness days 2 (0.3 vs. 0.5; P = .003), 3 (0.4 vs. 0.8; P = .0003), 4 (0.3 vs. 0.5; P = .025), and 5 (0.1 vs. 0.3; P = .03); sneeze counts for infected evaluable subjects (vs. counts for those who received placebo) were reduced on illness days 2 (1.5 vs. 3.1; P = .01), 3 (1.7 vs. 5.6; P = .0001), and 5 (0.7 vs. 1.9; P = .03). Infected evaluable subjects who received treatment had reduced rhinorrhea scores (compared with those who received placebo) on illness days 2 (0.7 vs. 1.0; P = .04) and 3 (0.6 vs. 0.9; P = .04) and had reduced nasal secretion weights on day 3 (3.6 g vs. 6.3 g; P = .03). Over 4 days of treatment, mean sneeze scores for infected evaluable subjects (vs. scores for those who received placebo) were reduced by 50%, mean sneeze counts by 57%, mean rhinorrhea scores by 27%, and mean nasal secretion weights by 35%. Other cold symptoms were unaffected by treatment. Treatment with clemastine was associated with an excess incidence of dry mouth (6%), dry nose (19%), and dry throat (17%).

Administration, Intranasal↗