Effects Of H1 Antagonists Research Articles

Parkinsonism Attenuation by Antihistamines via Downregulating the Oxidative Stress, Histamine, and Inflammation.

Parkinson disease (PD) is a neurodegenerative disorder of the motor activity of the brain, regulated by dopaminergic neurons of substantia nigra, resulting in an increased density of histaminergic fibers. This study was aimed to evaluate the effects of H1 antagonist’s ebastine and levocetirizine in PD per se and in combination. Animals were divided into 9 groups (n = 10). Group 1 received carboxymethyl cellulose CMC (1 mL/kg). Group II was treated with haloperidol (1 mg/kg) (diseased group). Group III was treated with levodopa/carbidopa (levo 20 mg/kg). Groups IV and V were treated with ebastine at dose levels of 2 and 4 mg/kg, respectively. Groups VI and VII were treated with levocetirizine at dose levels of 0.5 and 1 mg/kg, respectively. Group VIII was treated with ebastine (4 mg/kg) + levo (20 mg/kg) in combination. Group IX was treated with levocetirizine (1 mg/kg) + levo (20 mg/kg). PD was induced with haloperidol (1 mg/kg iv, once daily for 23 days) for a duration of 30 min. Behavioral tests like rotarod, block and triple horizontal bars, actophotometer, and open field were performed. Biochemical markers of oxidative stress, i.e., SOD, CAT, GSH, MDA, dopamine, serotonin, and nor-adrenaline and nitrite, were determined. Histamine, mRNA expression of α-synuclein, and TNF-α level in the serum and brain of mice were analyzed. Endogenous biochemical markers were increased except mRNA expression of α-synuclein, which was reduced. In combination therapy with the standard drug, ebastine (4 mg/kg) significantly improved the cataleptic state and dopamine levels, but no significant difference in the renal and liver functioning tests was observed. This study concluded that ebastine (4 mg/kg) might work in the treatment of PD as it improves the cataleptic state in haloperidol-induced catalepsy.

The potential impact of 1st and 2nd generation antihistamines on male fertility

Histamine antagonists are medications used to block the action of histamine at histamine receptors. H1 antagonists are mainly taken to reverse the effects of histamine during allergic reactions. Cetirizine hydrochloride and pheniramine maleate are the most clinically used H1 antihistamines; they have common tolerable side effects such as sedation, dizziness, fatigue, dry mouth, and nausea. The effect of H1 antagonists on male hormones and its outcomes on male fertility are still unclear. The aim of the present study was to evaluate the possible effects of both cetirizine and pheniramine maleate on male fertility. Measurement of prolactin, FSH, and LH serum levels and sperm count during chronic use. Cetirizine hydrochloride significantly increased prolactin levels compared with pheniramine maleate and control groups. Hyperprolactinemia significantly decreased FSH and LH levels and sperm count in the cetirizine hydrochloride treated group. In conclusion, this study reports that the second-generation antihistamine cetirizine hydrochloride has potent and significant effects on male fertility compared with the first-generation H1 antihistamine pheniramine maleate through its changes in prolactin, LH, and FSH levels. These hormonal changes decreased spermatogenesis and sperm count.

Novel Developments in the Pharmacological Management of Insomnia

Advances in the basic science of sleep/wake neurophysiology are driving the exploration of new pharmacologic approaches with continued improvement in efficacy and safety.

Comparative investigations of the influence of H1-antihistamines on the generation of reactive oxygen species by phagocytes

In addition to their antihistamine effects, H1-receptor antagonists possess pharmacological properties that are not uniformly distributed among this class of drugs, such as antiinfl ammatory effects, antiplatelet activity, supression of respiratory burst of professional phagocytes [1]. In our previous study, we compared the effects of dithiaden and another selected H1-antihistamines on the production of reactive oxygen species (ROS) by stimulated phagocytes [2]. Since the antioxidative effects of H1-antagonists are closely related to their anti-infl ammatory activity, we have compared fourteen H1-antihistamines from different pharmacological generations on the respiratory burst of phagocytes and their antioxidative properties in cell-free systems in vitro.

Stimulating Effects of H1-Antagonists

Whereas antihistamines are generally known for their sedative side effects, this review shows that several studies also found mild stimulating effects on performance for the H1-antagonists terfenadine, ebastine, fexofenadine and desloratadine. These stimulating effects were mostly demonstrated in tasks involving high levels of attention, e.g. divided attention tasks, vigilance tasks and driving tasks. The stimulating effects of these antihistamines were often dependent of the given dose; however the relation was not always linear. The mechanism responsible for the stimulating effects of these four antihistamines is still unclear, though it is hypothesized that it involves other neurotransmitters like dopamine and GABA, or that it acts through the H3 histamine receptor. Further research is needed to clarify the ambiguous role of histamine in processes of arousal. In addition, it would be useful to determine whether terfenadine, ebastine, fexofenadine and desloratadine can return allergic patient's performance back to their preclinical level.

Minimal role for H1and H2histamine receptors in cutaneous thermal hyperemia to local heating in humans

The precise mechanism(s) underlying the thermal hyperemic response to local heating of human skin are not fully understood. The purpose of this study was to investigate a potential role for H1 and H2 histamine-receptor activation in this response. Two groups of six subjects participated in two separate protocols and were instrumented with three microdialysis fibers on the ventral forearm. In both protocols, sites were randomly assigned to receive one of three treatments. In protocol 1, sites received 1) 500 microM pyrilamine maleate (H1-receptor antagonist), 2) 10 mM L-NAME to inhibit nitric oxide synthase, and 3) 500 microM pyrilamine with 10 mM NG-nitro-L-arginine methyl ester (L-NAME). In protocol 2, sites received 1) 2 mM cimetidine (H2 antagonist), 2) 10 mM L-NAME, and 3) 2 mM cimetidine with 10 mM L-NAME. A fourth site served as a control site (no microdialysis fiber). Skin sites were locally heated from a baseline of 33 to 42 degrees C at a rate of 0.5 degrees C/5 s, and skin blood flow was monitored using laser-Doppler flowmetry (LDF). Cutaneous vascular conductance was calculated as LDF/mean arterial pressure. To normalize skin blood flow to maximal vasodilation, microdialysis sites were perfused with 28 mM sodium nitroprusside, and control sites were heated to 43 degrees C. In both H1 and H2 antagonist studies, no differences in initial peak or secondary plateau phase were observed between control and histamine-receptor antagonist only sites or between L-NAME and L-NAME with histamine receptor antagonist. There were no differences in nadir response between L-NAME and L-NAME with histamine-receptor antagonist. However, the nadir response in H1 antagonist sites was significantly reduced compared with control sites, but there was no effect of H2 antagonist on the nadir response. These data suggest only a modest role for H1-receptor activation in the cutaneous response to local heating as evidenced by a diminished nadir response and no role for H2-receptor activation.

Effect of H1 Antagonists on the Progressive Growth of T Cell Lymphoma

The present investigation was undertaken to study the effect of H1 antihistaminic drugs: Chloropheniramine maleate (CPM) and Fexofenadine hydrochloride (Fx) on the progressive growth of a murine transplantable T cell lymphoma of spontaneous origin, designated as Dalton's Lymphoma (DL), and on the immune responses of the DL-bearing host. Administration of CPM and Fx to DL-bearing mice resulted in an augmentation of DL growth with an increase in the tumor cell count in Dl-bearing mice. Further, it was observed that there was a direct influence of the two drugs on DL cell proliferation. CPM and Fx augmented DL cell proliferation 1.4 and 1.5 folds, respectively. In vitro administration of CPM and Fx resulted in an increase in the count of splenocytes whereas that of thymocytes and bone marrow cells remained unchanged. However, splenocytes and thymocytes obtained from CPM and Fx administered mice showed an enhanced in vivo proliferation. CPM and Fx were found to enhance production of IL-1 by macrophages in the presence of LPS, which could be an additional indirect mode of the action of CPM and Fx on DL cell growth. These results may have clinical significance for patients-bearing lymphoma if undergoing treatment with CPM and Fx.

Involvement of histamine H3 receptors in scratching behaviour in mast cell-deficient mice.

Although the roles of histamine H3 receptors have been studied in several tissues such as the brain, lung, spleen, colon and peripheral sensory nerve endings, the involvement of H3 receptors in skin responses particularly in relation to scratching behaviour are not well documented. This work was performed to study the effects of histamine H3 antagonists on scratching behaviour in mast cell-deficient mice. Histamine H3 antagonists iodophenpropit and clobenpropit, histamine and substance P were injected intradermally into the rostral part of the back of mast cell-deficient (WBB6F1 W/Wv) and wild-type (WBB6F1+/+) mice and scratching behaviour was measured for 60 min. The effects of H1 antagonists on scratching behaviour induced by H3 antagonists were also investigated. Intradermal injection of iodophenpropit and clobenpropit at doses of 10 and 100 nmol per site caused significant increases in scratching behaviour in both mast cell-deficient and wild-type mice. Histamine also caused a dose-related increase in the incidence of scratching behaviour, and a significant effect was observed at a dose of 100 nmol per site in both mast cell-deficient and wild-type mice. Substance P was also effective in causing scratching behaviour in both mast cell-deficient and wild-type mice. However, histamine H1 antagonists diphenhydramine and chlorphenamine failed to inhibit H3 antagonist-induced scratching behaviour in both types of mice. Our results indicated that intradermal injection of H3 antagonists induces scratching behaviour and that chemical mediators other than histamine seem to be involved in the response.

Effect of H2-antagonist Rx-to-OTC switch in the US, UK and Canada

Effect of H2-antagonist Rx-to-OTC switch in the US, UK and Canada

Effects of H1 Antagonists on Cholinomimetic-Induced Tremulous Jaw Movements: Studies of Diphenhydramine, Doxepin, and Mepyramine

In several previous studies, tremulous jaw movements in rats have been used to assess the effects of antiparkinsonian drugs and atypical antipsychotics. Because antihistamines such as diphenhydramine are used as antiparkinsonian agents, and atypical antipsychotic drugs such as clozapine and olanzapine have high affinity for histamine H1 receptors, the present study investigated the effects of H1 antagonists on cholinomimetic-induced jaw movements. Diphenhydramine, doxepin, and mepyramine (all injected IP 2.5–20.0 mg/kg) were assessed for their ability to block the jaw movements induced by 5.0 mg/kg of the anticholinesterase tacrine. Within this dose range, only diphenhydramine produced a robust and significant reduction in jaw movement activity. Thus, diphenhydramine was subjected to further testing, which employed procedures previously used to assess the effects of other antitremorogenic drugs, such as clozapine. Diphenhydramine did not induce jaw movement activity. In addition to suppressing jaw movement activity after acute injections, diphenhydramine also suppressed tacrine-induced jaw movements after repeated (14-day) administration. In summary, the present results show that diphenhydramine suppresses cholinomimetic-induced jaw movements, an effect that is similar to other antiparkinsonian or antitremor drugs such as anticholinergics, L-DOPA, DA antagonists, and clozapine. Nevertheless, doxepin produced only mild effects, and mepyramine, which has a higher affinity and selectivity than diphenhydramine for H1 receptors, failed to suppress cholinomimetic-induced jaw movements. These results suggest that diphenhydramine suppresses tremulous movements through a mechanism that does not depend upon antagonism of histamine H1 receptors.

Modulation of the tight junctions of the Caco-2 cell monolayers by H2-antagonists.

The tight junctions in the intestinal epithelium represent highly specialized intercellular junctions. Ranitidine, an H2-antagonist, causes a tightening of the tight junctions. Hence, we have investigated the effect of ranitidine and other H2-antagonists on the function of the intestinal tight junctions. Effect of the H2-antagonists on the tight junctions has been investigated using the transepithelial electrical resistance (TEER) and the transport of mannitol across the Caco-2 cell monolayers. Four different H2-antagonists caused an increase in the TEER across the Caco-2 cell monolayers, accompanied by a decrease in the permeability for mannitol. The effect was concentration-dependent and saturable. Ranitidine and famotidine, caused a decrease in their own transport rate across the Caco-2 cells. Ranitidine competitively inhibited the increase in TEER caused by famotidine, whereas compounds which represent molecular fragments of ranitidine had no effect. The relative potency of the four H2-antagonists in causing an increase in the TEER correlated inversely with the oral bioavailability of these compounds in humans. We hypothesize that the H2-antagonists exert their effect on the tight junctions of Caco-2 cells by modulation of interactions among proteins associated with the tight junctional complex.

Generalization of D-, L- and DL-chlorpheniramine and zolantidine to the discriminative stimulus effects of cocaine and methamphetamine.

We recently demonstrated that some H-antagonists have cocaine or methamphetamine-like discriminative stimulus effects. In the present study, the effects of optical isomers of chlorpheniramine (D-, L- and DL-forms) on the discriminative stimulus effects of cocaine and methamphetamine were examined in rats trained to discriminate between cocaine (10.0 mg/kg) or methamphetamine (1.0 mg/kg) and saline, to determine whether these effects of H1-antagonists are mediated by the blockade of H-receptors. In generalization tests with optical isomers of chlorpheniramine, the D-, L- and DL-forms all completely generalized to the discriminative stimulus effects of cocaine, but did not generalize to those of methamphetamine. Dose-generalization by the optical isomers of chlorpheniramine to the discriminative stimulus effects of cocaine did not correlate with the H-antagonistic potency of these drugs. These results suggest that all of the optical isomers of chlorpheniramine have cocaine-like discriminative stimulus effects, but that these effects are not mediated by H1-receptor blockade. On the other hand, the H2-antagonist, zolantidine, generalized to the discriminative stimulus effects of methamphetamine, but not to those of cocaine, suggesting that zolantidine may have methamphetamine-like discriminative stimulus effects. In the present study, GBR12909 (dopamine uptake inhibitor) completely generalized to the discriminative stimulus effects of cocaine, but not to those of methamphetamine, whereas apomorphine (dopamine receptor agonist) generalized more potently to the discriminative stimulus effects of methamphetamine than to those of cocaine. These findings imply that although the dopaminergic system plays an important role in the discriminative stimulus effects of both cocaine and methamphetamine, there may be differences between their effects.

Interactions between H1-antagonists and opioids: a drug discrimination study.

We previously demonstrated that combination of opioids, pentazocine and dihydrocodeine, with the histamine H1-receptor antagonists tripelennamine and chlorpheniramine could enhance their rewarding effects in rats. In the present study, the effects of combined treatment with opioids and H1-antagonists on discriminative stimulus effects were examined in rats trained to discriminate between cocaine (10 mg/kg) or morphine (3.0 mg/kg) and saline, since it is believed that discriminative stimulus effects of abused drugs are related to their rewarding effects. Tripelennamine and chlorpheniramine, but not pentazocine or dihydrocodeine, generalized to the discriminative stimulus effects of cocaine. Pentazocine (3.0 mg/kg) and dihydrocodeine (5.6 mg/kg) significantly potentiated the cocaine-like discriminative stimulus effects of low doses of tripelennamine and chlorpheniramine, respectively. On the other hand, pentazocine and dihydrocodeine, but not tripelennamine or chlorpheniramine, generalized to the discriminative stimulus effects of morphine. Neither 1.0 or 3.0 mg/kg tripelennamine nor chlorpheniramine affected the morphine-like discriminative stimulus effects of pentazocine and dihydrocodeine, respectively. These results suggest that the potentiation of the cocaine-like discriminative stimulus effects of H1-antagonists by opioids may be involved in the enhanced rewarding effects of combinations of opioids and H1-antagonists.

P-125 - Effects of H1-antagonists on radial arm maze performance in rats

P-125 - Effects of H1-antagonists on radial arm maze performance in rats

Effects of H1-antagonists on discriminative stimulus effects of cocaine and methamphetamine in rats

The effects of H(1)-antagonists, such as tripelennamine, chlorpheniramine and pyrilamine, on the discriminative stimulus effects of cocaine and methamphetamine in rats were examined. Rats were trained to discriminate between cocaine (10mg/kg, i.p.) or methamphetamine (1.0mg/kg, i.p.) and saline, with responses maintained under a fixed-ratio 10 (FR10) schedule of food delivery. In generalization tests, tripelennamine generalized to the discriminative stimulus effects of cocaine and methamphetamine, while chlorpheniramine only generalized to cocaine. These generalizations of tripelennamine and chlorpheniramine were attenuated by the dopamine receptor antagonist haloperidol. Furthermore, tripelennamine and chlorpheniramine, but not pyrilamine, potentiated the discriminative stimulus effects of cocaine and methamphetamine. These results suggest that some H(1)-antagonists possess cocaine- and/or methamphetamine-like discriminative stimulus effects which may be mediated by the dopaminergic system, and as a result the discriminative stimulus effects of cocaine and methamphetamine were potentiated by these H(1)-antagonists.

Once-Daily Bedtime Dose of Roxatidine and Ranitidine in Acute Duodenal Ulcer: A Combined Assessment of Acid Inhibitory Activity and Healing Rate.

This study was carried out in order to compare the antisecretory effect of a single bedtime dose of roxatidine 150 mg and ranitidine 300 mg and to assess the relationship between the degree and the duration of acid suppression and the healing rates obtained in duodenal ulcer patients treated with the above regimens. Sixty-three patients with endoscopically proven ulcer underwent 24-h gastric pH-metry on day 0, day 1, and day 28 of treatment with both roxatidine and ranitidine. Ulcer healing was checked endoscopically after 4 weeks of therapy. RESULTS: Eight patients did not complete the study, leaving 55 patients eligible for final analysis, 28 in the roxatidine group and 27 in the ranitidine group. Duodenal ulcers were healed in 24--28 (85%) patients of the former and in 22--27 (81%) patients of the latter group (p minus sign NS). Gastric pH was significantly higher (p < 0.001) than basal values on days 1 and 28 with both H2-antagonists. The 24-h pH levels did not differ between day 1 and day 28 with both roxatidine and ranitidine. There was also do difference between the two active treatments. The pattern of gastric acidity significantly differed (p < 0.01) between responder (n = 46) and nonresponder (n = 9) patients to both H2-blockers, and this difference was mainly sustained by nocturnal pH. CONCLUSIONS: A bedtime close of roxatidine 150 mg and ranitidine 300 mg was able to heal more than 80% of duodenal ulcers within 4 weeks of treatment. The lack of tolerance to H2-blockers in duodenal ulcer patients contributes to this good result. The antisecretory effect of H2-antagonists is reduced in nonresponder patients with respect to responder patients and this is mainly due to an impaired control of nocturnal acidity.

Indomethacin induced changes in mucosal lysosomal enzyme activity: effect of H2 antagonists.

Indomethacin induced gastric damage in rats was accompanied by a decrease in mucosal activities of three lysosomal enzymes tested, with serum levels remaining unchanged. Petreatments with cimetidine (100 mg/kg b.w.) and ranitidine (30 mg/kg b.w.) were found partially to prevent the decrease of N-acetylglucosaminidase and acid phosphatase, as well as of beta-glucuronidase, while the latter was also prevented by famotidine (10 mg/kg b.w.). All the H2 antagonists tested reduced dose-dependently the extent of gastric injury induced by indomethacin and reversed the changes in protein levels. The stabilisation of lysosomal membranes and thus the prevention of lysosomal leakage may be one of the favourable additional mechanisms of antiulcer activity of H2 antagonists.

H2-Antagonists and Alcohol

There are conflicting data on the existence of significant first-pass metabolism of alcohol (ethanol) in the human stomach and its inhibition by histamine H2-receptor antagonists. Alcohol is predominantly metabolised in the liver by the microsomal alcohol oxidising system, alcohol dehydrogenase (ADH) and a catalase enzyme. Histochemical and kinetic studies have revealed several ADH isoenzymes in the gastric mucosa with different kinetic properties. After small oral doses of alcohol first-pass metabolism in the stomach occurs, as shown by reduced area under the plasma concentration-time curve (AUC) compared with intravenous or intraduodenal administration. The activity of gastric ADH is reduced in women, the elderly, Asian individuals, the fasting state, chronic alcoholism and after gastrectomy. The effect is only present with small (< or = 0.3 g/kg) alcohol doses and with a high alcohol concentration. In a number of studies, cimetidine in therapeutic doses over 7 days produced a significant increase in the AUC and in the peak plasma concentration after administration of alcohol 0.15 and 0.30 g/kg. This was related to an inhibition of gastric ADH activity, as shown by in vitro studies. Ranitidine inhibited gastric ADH to a similar extent on a molar basis, but its effect on alcohol levels in vivo was less constant in various studies. Nizatidine also reduced gastric alcohol first-pass metabolism, but famotidine and roxatidine did not show this effect. In other studies, H2-receptor antagonists did not change AUC and peak alcohol concentration. The controversy is not easy to resolve, since a number of the positive studies did not use a placebo-controlled, randomised, crossover design, while some of the negative studies did not exclude habitual alcohol consumers and included Oriental volunteers, although both groups have been shown to lack significant gastric ADH activity. In this case, when first-pass metabolism of alcohol does not exist, this by definition cannot be abolished by H2-antagonists. The inclusion of oral and intravenous dosage data of alcohol is mandatory to positively identify first-pass metabolism in any individuals. The significance of the effect of H2-antagonists on blood alcohol concentrations is minor. It only occurs in young, male, nonalcoholic, non-Asian individuals, and alcohol must be given in a small (social) dose, in a high concentration, and after meals. An increase in alcohol levels in predisposed patients during treatment with some H2-antagonists cannot be excluded, although the likelihood is small. Furthermore, carefully designed studies are needed to clarify fully the significance of this interaction.

The Hemodynamic Effects of H2 Antagonists in Intensive Care Unit Patients

Many critical care patients require intravenously ad ministered H2-receptor antagonists to reduce the acidity of gastric acid secretions and prevent the incidence of stress-related mucosal damage. These patients are often already hemodynamically compromised or unstable. The use of an H2-receptor antagonist that further com promises the cardiovascular status of these critically ill patients could prove detrimental.

The Effect of H2 Antagonists on Duration of Action of Suxamethonium in the Parturient

Summary Fifteen patients who underwent elective Caesarean section were given sodium citrate, either alone or combined with oral cimetidine or ranitidine, as antacid premedication. No significant diflerences in time to 25 or 50% recovery of the first twitch of a train-of-four after administration of suxamethonium were found between any of the groups. It is concluded that H2-antagonists do not significantly affect the duration of action of suxamethonium in parturients, in contrast to the findings of a study in nonpregnant patients.