Can ocean warming alter sub-lethal effects of antiepileptic and antihistaminic pharmaceuticals in marine bivalves?

The negative effects induced in marine organisms by Climate Change related abiotic factors consequences, namely ocean warming, are well-known. However, few works studied the combined impacts of ocean warming and contaminants, as pharmaceutical drugs. Carbamazepine (CBZ) and cetirizine (CTZ) occur in the marine environment, showing negative effects in marine organisms. This study aimed to evaluate the impacts of ocean warming on the effects of CBZ and CTZ, when acting individually and combined (drug vs drug), in the edible clam Ruditapes philippinarum. For that, drugs concentration, bioconcentration factors and biochemical parameters, related with clam's metabolic capacity and oxidative stress, were evaluated after 28 days exposure to environmentally relevant scenarios of these stressors. The results showed limited impacts of the drugs (single and combined) at control and warming condition. Indeed, it appeared that warming improved the oxidative status of contaminated clams (higher reduced to oxidized glutathione ratio, lower lipid peroxidation and protein carbonylation levels), especially when both drugs were combined. This may result from clam's defence mechanisms activation and reduced metabolic capacity that, respectively, increased elimination and limited production of reactive oxygen species. At low stress levels, defence mechanisms were not activated which resulted into oxidative stress. The present findings highlighted that under higher stress levels clams may be able to activate defence strategies that were sufficient to avoid cellular damages and loss of redox homeostasis. Nevertheless, low concentrations were tested in the present study and the observed responses may greatly change under increased pollution levels or temperatures. Further research on this topic is needed since marine heat waves are increasing in frequency and intensity and pollution levels of some pharmaceuticals are also increasing in coastal systems.

pH-Dependent Uptake and Sublethal Effects of Antihistamines in Zebrafish (Danio rerio) Embryos.

Reported off-target effects of antihistamines in humans draw interest in ecotoxicity testing of first- and second-generation antihistamines, the latter of which have fewer reported side effects in humans. Because antihistamines are ionizable compounds, the pH influences uptake and toxicity and thus is highly relevant when conducting toxicity experiments. Zebrafish embryo toxicity tests were performed with the 3 first-generation antihistamines ketotifen, doxylamine, and dimethindene and the 2 second-generation antihistamines cetirizine and levocabastine at pH 5.5, 7.0, and 8.0. We detected effects on survival, phenotype, swimming activity, and heart rate for 4 antihistamines with the exception of levocabastine, which did not show any lethal or sublethal effects. When compared to lethal concentrations, effect concentrations neither of phenotype malformation nor of swimming activity or heart rate deviated by more than a factor of 10 from lethal concentrations, indicating that all sublethal effects were fairly nonspecific. First-generation antihistamines are weak bases and showed decreasing external effect concentrations with increasing neutral fraction, accompanied by increased uptake in the fish embryo. As a result, internal effect concentrations were independent from external pH. The pH-dependent toxicity originates from speciation-dependent uptake, with neutral species taken up in higher amounts than the corresponding ionic species. Cetirizine, which shifts from a zwitterionic to an anionic state in the measured pH range, did not show any pH-dependent uptake or toxicity. Environ Toxicol Chem 2019;00:1-11. © 2019 SETAC.

Antiallergic and antihistaminic actions of Ceasalpinia bonducella seeds: Possible role in treatment of asthma.

ETHNOPHARMACOLOGICAL RELEVANCE: Seed kernel of the plant Ceasalpinia bonducella Linn (Caesalpiniacaeae) are used for the treatment of asthma in folk medicine and ancient books. AIM OF STUDY: To assess the pharmacological efficacy of the plant in asthma and to confine and describe the synthetic constituents from the seeds that are in charge of the action. MATERIAL AND METHODS: The viability of petroleum ether, ethanol extract and ethyl acetate fraction from ethanol extract of C. bonducella seeds were screened for the treatment of asthma by various methods viz. effect of test drug on clonidine and haloperidol induced catalepsy, milk-induced leukocytosis and eosinophilia, mast cell stabilizing activity in mice and studies on smooth muscle preparation of guinea pig ileum (in-vitro). Column chromatography of active extract was done to pinpoint the active compound followed by structure elucidation by FTIR, GCMS and NMR spectroscopic methods. RESULTS: Ethyl acetate fraction from ethanol extract of C. bonducella seeds exhibited antihistaminic activity at the dose of 50 and 100 mg/kg, inhibited clonidine-induced catalepsy but not haloperidol-induced catalepsy. Ethyl acetate fraction from ethanol extract significantly inhibited increased leukocyte and eosinophil count due to milk allergen and showed maximum protection against mast cell degranulation by clonidine. The results of guinea pig ileum indicated that the compound 2 methyl, 1 hexadecanol isolated from ethyl acetate fraction of ethanol extract relaxed significantly the ileum muscle strips pre-contracted by which suggests the involvement of ß2-agonists on the relaxation of the tissue. All the results are dose dependent. Active ethyl acetate fraction from ethanol extract showed presence of anti-asthmatic compound, 2-methyl, 1-hexadecanol. CONCLUSION: The ethyl acetate fraction from ethanol extract of seeds of the plant C. bonducella can inhibit parameters linked to asthma disease.

Genotoxicity of 4-(piperazin-1-yl)-8-(trifluoromethyl)pyrido[2,3-e][1,2,4] triazolo[4,3-a]pyrazine, a Potent H4 Receptor Antagonist for the Treatment of Allergy: Evidence of Glyoxal Intermediate Involvement.

BACKGROUND: 4-(piperazin-1-yl)-8-(trifluoromethyl)pyrido[2,3-e][1,2,4]triazolo[4,3-a]pyrazine (1) is a small-molecule which demonstrated a sub-nM inhibitory potency toward the histamine H4 receptor (H4R). However, it was found to be mutagenic in an in vitro Ames assay. Metabolic bioactivation of 1 could potentially arise from the piperazine moiety by forming reactive intermediates such as glyoxal, aldehyde-imine and/or iminium ion, which could all lead to genotoxicity. The aim of this study was to investigate bioactivation of 1 to determine the potential causes of the genotoxicity and mitigate liabilities in this scaffold. METHODS: 1 was investigated for its genotoxicity in phenobarbital and ß-naphthoflavone induced Sprague Dawley rat liver S9 fractions. Trapping agents such as o-phenylenediamine was used postincubation. RESULTS: Following metabolic profiling of 1, two oxidative metabolites were observed and identified in phenobarbital- and ß -naphthoflavone induced Sprague Dawley rat liver S9 fractions. Metabolic pathway of 1 was primarily mediated by the metabolism of the piperazine moiety. The trapped glyoxal was identified by using high resolution LC-MS instrument. Structural characterization of the trapped glyoxal was determined by comparison of retention time, accurate mass measurement and Collision Induced Dissociation (CID) spectra to authentic standard. CONCLUSION: In the present investigation, a novel method was developed to trap glyoxal, which may potentially be liberated from piperazine moiety. These findings led to modifications on the piperazine ring to mitigate the bioactivation pathways leading to mutagenicity. Subsequently, the next generation compounds with modified piperazine moiety, retained H4R inhibitory potency in vitro and were not genotoxic in the Ames mutagenicity assay.

An Immunohistochemical Investigation of Renal Phospholipidosis and Toxicity in Rats.

Immunohistochemical staining for the lysosome-associated membrane protein 2 (LAMP-2) has been proposed previously as an alternative to electron microscopy to identify hepatic phospholipidosis. This study used LAMP-2 immunohistochemistry (IHC) to diagnose phospholipidosis in rats exhibiting renal tubular injury. Rats were administered toreforant, a histamine H4 receptor antagonist by oral gavage at a dose of 3, 10, or 100 mg/kg/d for 6 months. Hematoxylin and eosin staining revealed renal tubular epithelial cell vacuolation, hypertrophy, degeneration, and luminal dilation in the 100 mg/kg/d group animals. Renal tubular injury was confirmed using kidney injury marker 1 (KIM-1) IHC. The involvement of phosopholipidosis in the renal injury was investigated by LAMP-2. Adipophilin IHC was included to differentiate phospholipidosis from lipidosis. Increased LAMP-2 staining was observed in the 100 mg/kg/d group animals when compared to vehicle group animals. Lysosome-associated membrane protein-2 staining was most prominent in the outer stripe of the outer medulla where KIM-1 staining was also most prominent. By contrast, adipophilin staining was not increased. Phospholipidosis was also confirmed by electron microscopy. These data support the use of LAMP-2 IHC as a diagnostic tool and suggest an association between phospholipidosis and the renal tubular injury caused by toreforant.

P21 (Cdc42/Rac)-activated kinase 1 (pak1) is associated with cardiotoxicity induced by antihistamines.

Astemizole, a non-sedating histamine H1 receptor blocker, is widely known to cause cardiac arrhythmia, which prolongs the QT interval. However, the precise molecular mechanism involved in antihistamine-induced cardiovascular adverse effects other than hERG channel inhibition is still unclear. In this study, we used DNA microarray analysis to detect the mechanisms involved in life-threatening adverse effects caused by astemizole. Rat primary cardiomyocytes were treated with various concentrations of astemizole for 24 h and the corresponding cell lysates were analyzed using a DNA microarray. Astemizole altered the expression profiles of genes involved in calcium transport/signaling. Using qRT-PCR analysis, we demonstrated that, among those genes, p21 (Cdc42/Rac)-activated kinase 1 (pak1) mRNA was downregulated by treatment with terfenadine and astemizole. Astemizole also reduced pak1 protein levels in rat cardiomyocytes. In addition, astemizole decreased pak1 mRNA and protein levels in H9c2 cells and induced an increase in cell surface area (hypertrophy) and cytotoxicity. Fingolimod hydrochloride (FTY720), a pak1 activator, inhibited astemizole-induced hypertrophy and cytotoxicity in H9c2 cells. These results suggest that antihistamine-induced cardiac adverse effects are associated with pak1 expression and function.

Effects of an antihistamine on carbon and nutrient recycling in streams.

In stream ecosystems, microbes and macroinvertebrates consume leaf litter deposited from the riparian vegetation, and thereby recycle resources tied up in the litter. Several environmental variables influence rates of this recycling, but it is not well known if common pharmaceuticals, such as antihistamines, originating from wastewater effluent, have additional impacts. Exposure to dilute concentrations of antihistamines may adversely influence aquatic detritivorous invertebrates, because invertebrates use histamines for neurotransmission, resulting in hampered recycling of resource tied up in leaf detritus. In this study, we therefore investigated if the antihistamine fexofenadine, at a concentration of 2000ngl(-1), alters rates of leaf litter decomposition in stream microcosms. Stonefly larvae (n=10, per microcosm), together with natural microbial communities, served as main decomposer organisms on alder leaf litter. First, we used 30 microcosms containing fexofenadine, while the other 30 served as non-contaminated controls, and of each 30 microcosms, 14 contained stonefly larvae and microbes, while the remaining 16 contained only microbes. We found, in contrast to our hypothesis, that fexofenadine had no effect on leaf litter decomposition via impacts on the stonefly larvae. However, independent on if stoneflies were present or not, concentrations of organic carbon (TOC) and nitrogen (N) were strongly affected, with 20-26 and 24-31% lower concentrations of TOC and N, respectively, in the presence of fexofenadine. Second, in a scaled down follow-up experiment, we found that microbial activity increased by 85%, resulting in a 10% decrease in pH, in the presence of fexofenadine. While the antihistamine concentration we used is higher than those thus far found in the field (1-10ngl(-1)), it is still 100 times lower than the predicted no-effect concentration for fexofenadine. As such, our results indicate that low µg l(-1) levels of antihistamines can have an effect on carbon and nutrient recycling in aquatic system.

Comparative pharmacology and toxicology of pharmaceuticals in the environment: diphenhydramine protection of diazinon toxicity in Danio rerio but not Daphnia magna.

Pharmaceuticals and other contaminants of emerging concern present unique challenges to environmental risk assessment and management. Fortunately, mammalian pharmacology and toxicology safety data are more readily available for pharmaceuticals than other environmental contaminants. Identifying approaches to read-across such pharmaceutical safety information to non-target species represents a major research need to assess environmental hazards. Here, we tested a biological read-across hypothesis from emergency medicine with common aquatic invertebrate and vertebrate models. In mammals, the antihistamine diphenhydramine (DPH) confers protection from poisoning by acetylcholinesterase inhibition because DPH blocks the acetylcholine receptor. We employed standardized toxicity methods to examine individual and mixture toxicity of DPH and the acetylcholinesterase inhibitor diazinon (DZN) in Daphnia magna (an invertebrate) and Danio rerio (zebrafish, a vertebrate). Though the standardized Fish Embryo Toxicity method evaluates early life stage toxicity of zebrafish (0-3 days post fertilization, dpf), we further evaluated DPH, DZN, and their equipotent mixture during three development stages (0-3, 3-6, 7-10 dpf) in zebrafish embryos. Independent action and concentration addition mixture models and fish plasma modeling were used to assist interpretation of mixture toxicity experiments. Though our primary hypothesis was not confirmed in acute studies with Daphnia magna, DPH conferred a protective effect for acute DZN toxicity to zebrafish when DPH plasma levels were expected to be greater than mammalian therapeutic, but lower than acutely lethal, internal doses. We further observed that timing of developmental exposure influenced the magnitude of DZN and DPH toxicity to zebrafish, which suggests that future zebrafish toxicity studies with pharmaceuticals and pesticides should examine exposure during developmental stages.

Antihistamines modulate the integrin signaling pathway in h9c2 rat cardiomyocytes: Possible association with cardiotoxicity.

The identification of biomarkers for toxicity prediction is crucial for drug development and safety evaluation. The selective and specific biomarkers for antihistamines-induced cardiotoxicity is not well identified yet. In order to evaluate the mechanism of the life-threatening effects caused by antihistamines, we used DNA microarrays to analyze genomic profiles in H9C2 rat cardiomyocytes that were treated with antihistamines. The gene expression profiles from drug-treated cells revealed changes in the integrin signaling pathway, suggesting that cardiac arrhythmias induced by antihistamine treatment may be mediated by changes in integrin-mediated signaling. It has been reported that integrin plays a role in QT prolongation that may induce cardiac arrhythmia. These results indicate that the integrin-mediated signaling pathway induced by antihistamines is involved in various biological mechanisms that lead to cardiac QT prolongation. Therefore, we suggest that genomic profiling of antihistamine-treated cardiomyocytes has the potential to reveal the mechanism of adverse drug reactions, and this signal pathway is applicable to prediction of in vitro cardiotoxicity induced by antihistamines as a biomarker candidate.

Antihistamines.

The discovery of histamine, its physiological role and reversal of its pharmacological effects by antihistamines takes us on a journey through the origins of modern physiology and the rising understanding of pharmacology at the end of the 19th and the early part of the 20th centuries. This journey, which has been traced in the excellent historical review by Michael Emanuel [Clin Exp Allergy 1999;29:1-11], is populated by some of the greatest scientists of the era, including six Nobel laureates - Bovet, Dale, Ehrlich, Richet, Windaus and Black. In addition, it laid the basis of medicinal chemistry not only for antihistamines, but also for the discovery of a plethora of drugs still in use today.

Mechanism of the histamine H(3) receptor-mediated increase in exploratory locomotor activity and anxiety-like behaviours in mice.

Histaminergic neurons are activated by histamine H(3) receptor (H(3)R) antagonists, increasing histamine and other neurotransmitters in the brain. The prototype H(3)R antagonist thioperamide increases locomotor activity and anxiety-like behaviours; however, the mechanisms underlying these effects have not been fully elucidated. This study aimed to determine the mechanism underlying H(3)R-mediated behavioural changes using a specific H(3)R antagonist, JNJ-10181457 (JNJ). First, we examined the effect of JNJ injection to mice on the concentrations of brain monoamines and their metabolites. JNJ exclusively increased N(τ)-methylhistamine, the metabolite of brain histamine used as an indicator of histamine release, suggesting that JNJ dominantly stimulates the release of histamine release but not of other monoamines. Next, we examined the mechanism underlying JNJ-induced behavioural changes using open-field tests and elevated zero maze tests. JNJ-induced increase in locomotor activity was inhibited by α-fluoromethyl histidine, an inhibitor of histamine synthesis, supporting that H(3)R exerted its effect through histamine neurotransmission. The JNJ-induced increase in locomotor activity in wild-type mice was preserved in H(1)R gene knockout mice but not in histamine H2 receptor (H(2)R) gene knockout mice. JNJ-induced anxiety-like behaviours were partially reduced by diphenhydramine, an H(1)R antagonist, and dominantly by zolantidine, an H(2)R antagonist. These results suggest that H(3)R blockade induces histamine release, activates H(2)R and elicits exploratory locomotor activity and anxiety-like behaviours.

Antihistamines and aquatic insects: bioconcentration and impacts on behavior in damselfly larvae (Zygoptera).

Because aquatic insects use histamines as neurotransmitters, adverse impacts on aquatic insects living in aquatic environments that receive antihistamines with wastewater effluent are plausible. In this study, we exposed damselfly larvae to low concentrations of two commonly used antihistamines (Hydroxyzine and Fexofenadine, 360 ± 42 and 2,200 ± 43 ng l(-1), respectively), and recorded damselfly larvae behavior before and after exposure. Further, after the second set of behavioral assays was performed, we quantified bioconcentration of the antihistamines in the damselfly bodies. Our results showed significant changes in damselfly behavior following antihistamine exposure. After Hydroxyzine exposure, the damselfly larvae became less active, and they showed reduced fleeing response (i.e. increased boldness) after being exposed to Fexofenadine, the latter also being significantly different from the non-exposed (control) individuals. Further, we found high levels of bioconcentration in the damselflies; Hydroxyzine showed an average bioconcentration factor (BCF) of 2000. As such, our results indicate that low concentrations of antihistamines can have sub-lethal effects on aquatic insects manifested as behavioral changes, and that bioconcentration of these substances can be high. Therefore, the need to investigate the impact of emergent aquatic contaminants also on aquatic insects, and on behaviors that are of ecological importance, is further highlighted.

Antihistaminic and antiallergic actions of extracts of Solanum nigrum berries: possible role in the treatment of asthma.

ETHNOPHARMACOLOGICAL RELEVANCE: Berries of the plant Solanum nigrum Linn (Solanaceae) are used for the treatment of asthma in folk medicine and ancient books. AIM OF STUDY: To evaluate potential of the plant berries in the treatment of asthma. MATERIALS AND METHODS: Petroleum ether, ethanol and aqueous extracts of S. nigrum berries (50, 100 and 200mg/kg, i.p.) were screened for the treatment of asthma by the various methods viz. effect on clonidine and haloperidol induced catalepsy, milk-induced leucocytosis and eosinophilia, mast cell stabilizing activity in mice and studies on smooth muscle preparation of guinea pig ileum (in vitro). Active petroleum ether extract was standardized by HPTLC. RESULTS: The petroleum ether extract of S. nigrum berries inhibited clonidine-induced catalepsy significantly but not haloperidol-induced catalepsy. Petroleum ether extract significantly inhibited increased leukocyte and eosinophil count due to milk allergen and showed maximum protection against mast cell degranulation by clonidine. Petroleum ether extract resisted contraction induced by histamine better than other extracts. All the results are dose dependant. Active petroleum ether extract showed presence of antiasthmatic compound, ß-sitosterol. CONCLUSION: The petroleum ether extract of S. nigrum berries can inhibits parameters linked to the asthma disease.

Immunological, biochemical and histopathological evaluation of histamine receptors (H1R, H2R, H3R and H4R)-antagonist in rabbit experimental model: a short term study.

The present study was designed to delineate the immuno- and hepatotoxicological roles of HRs-antagonists in vivo which is elementary in existing literature. The cohort comprised of two experimental studies. Experimental study 1 was designed for immunological investigations and consisted of seven groups and immunized with intravenous injection of SRBC at day 3 containing six rabbits each. Experimental study 2 was designed to assess the functional status of liver and comprised of seven groups containing five rabbits each. In both experimental studies group-I received sterile distilled water intramuscularly, and group II-VI received subcutaneous histamine, pheniramine (H1R-antagonist), ranitidine (H2R-antagonist), iodophenpropit (H3R-antagonist) and JNJ7777120 (H4R-antagonist), respectively while group-VII received DMSO intramuscularly. ELISA was used to assess the immunological investigations. The SRBC-specific immunoglobulins (Igs), IgM and IgG were significantly increased (p<0.05). Hepatotoxicity due to same histamine and HRs-antagonists were demonstrated by biochemical and histopathological methods. Rabbits in group II-VI had significantly (p<0.05) elevated levels of serum enzymes (ALT, AST, ALP) and bilirubin. Histopathological examination showed maintained hepatic lobular architecture in histamine and DMSO-treated groups a kin to control. Notable findings in other groups included increased binuclearity in H1R, trinuclearity in H2R, oxyphilic clusters of hepatocytes in H3R and moderate centrilobular necrosis in H3R and H4R-antagonist-treated groups without obvious inflammatory cell infiltration and Kupffer cell prominence. It is concluded that HRs-antagonist play immune suppressive role through H1R, H2R and H4R while immune enhancing role through H3R. In addition, HRs-antagonists appear moderately hepatotoxic in terms of altered serum enzyme levels and non-inflammatory hepatocellular damage.

Discovery of two clinical histamine H(3) receptor antagonists: trans-N-ethyl-3-fluoro-3-[3-fluoro-4-(pyrrolidinylmethyl)phenyl]cyclobutanecarboxamide (PF-03654746) and trans-3-fluoro-3-[3-fluoro-4-(pyrrolidin-1-ylmethyl)phenyl]-N-(2-methylpropyl)cyclobutanecarboxamide (PF-03654764).

The discovery of two histamine H(3) antagonist clinical candidates is disclosed. The pathway to identification of the two clinical candidates, 6 (PF-03654746) and 7 (PF-03654764) required five hypothesis driven design cycles. The key to success in identifying these clinical candidates was the development of a compound design strategy that leveraged medicinal chemistry knowledge and traditional assays in conjunction with computational and in vitro safety tools. Overall, clinical compounds 6 and 7 exceeded conservative safety margins and possessed optimal pharmacological and pharmacokinetic profiles, thus achieving our initial goal of identifying compounds with fully aligned oral drug attributes, "best-in-class" molecules.

Discovery and characterization of 6-{4-[3-(R)-2-methylpyrrolidin-1-yl)propoxy]phenyl}-2H-pyridazin-3-one (CEP-26401, irdabisant): a potent, selective histamine H3 receptor inverse agonist.

Optimization of a novel series of pyridazin-3-one histamine H(3) receptor (H(3)R) antagonists/inverse agonists identified 6-{4-[3-(R)-2-methylpyrrolidin-1-yl)propoxy]phenyl}-2H-pyridazin-3-one (8a, CEP-26401; irdabisant) as a lead candidate for potential use in the treatment of attentional and cognitive disorders. 8a had high affinity for both human (K(i) = 2.0 nM) and rat (K(i) = 7.2 nM) H(3)Rs with greater than 1000-fold selectivity over the hH(1)R, hH(2)R, and hH(4)R histamine receptor subtypes and against an in vitro panel of 418 G-protein-coupled receptors, ion channels, transporters, and enzymes. 8a demonstrated ideal pharmaceutical properties for a CNS drug in regard to water solubility, permeability and lipophilicity and had low binding to human plasma proteins. It weakly inhibited recombinant cytochrome P450 isoforms and human ether-a-go-go-related gene. 8a metabolism was minimal in rat, mouse, dog, and human liver microsomes, and it had good interspecies pharmacokinetic properties. 8a dose-dependently inhibited H(3)R agonist-induced dipsogenia in the rat (ED(50) = 0.06 mg/kg po). On the basis of its pharmacological, pharmaceutical, and safety profiles, 8a was selected for preclinical development. The clinical portions of the single and multiple ascending dose studies assessing safety and pharmacokinetics have been completed allowing for the initiation of a phase IIa for proof of concept.

Genotoxicity and carcinogenicity studies of antihistamines.

This review provides a compendium of the results of genotoxicity and carcinogenicity assays performed on marketed antihistamines. Of the 70 drugs examined, 29 (41.4%) have at least one genotoxicity and/or carcinogenicity test result: 12 tested positive in at least one genotoxicity assay, six in at least one carcinogenicity assay, and four gave a positive response in both at least one genotoxicity assay and at least one carcinogenicity assay. Of 19 drugs with both genotoxicity and carcinogenicity data, eight were neither genotoxic nor carcinogenic, two were carcinogenic in at least one sex of mice or rats but tested negative in genotoxicity assays, five tested positive in at least one genotoxicity assay but were non-carcinogenic, and four gave a positive response in at least one genotoxicity assay and in at least one carcinogenicity assay. Only 12 (17.1%) of the 70 drugs examined have all data required by present guidelines for testing of pharmaceuticals, but it should be considered that a large fraction of them were developed and marketed prior the present regulatory climate.

Chronic toxicity of diphenhydramine hydrochloride and erythromycin thiocyanate to daphnia, Daphnia magna, in a continuous exposure test system.

Diphenhydramine hydrochloride (DH; Benadryl™, an over-the-counter antihistamine) and erythromycin thiocyanate (ET; a commonly used macrolide antibiotic) are pharmaceutical compounds whose chronic toxicity to Daphnia magna had not been characterized. Continuous exposure to DH concentrations about 5 times greater than the maximum reported environmental concentration of 0.023 µg/L for 21 days or to ET concentrations about 40 times the maximum reported environmental concentration of 6 µg/L for 21 days did not significantly impact D. magna survival and production. In this study the no observable effect concentration for DH was 0.12 µg/L and for ET was 248 µg/L.

Topological models for prediction of physico-chemical, pharmacokinetic and toxicological properties of antihistaminic drugs using decision tree and moving average analysis.

Various topostructural and topochemical indices were used to encode the structureal features of antihistaminic drugs. The values of 18 indices for each drug comprising the dataset were computed using an in-house computer program. In the present study, decision tree and moving average analysis were used to predict physico-chemical (log P), pharmacokinetic (T(max)) and toxicological properties (LD(50)) of antihistaminic drugs. A decision tree was constructed for each property to determine the importance of Topological Indices (TIs). Single topological index based models were developed using moving average analysis. The tree learned the information from the input data with an accuracy of >94% and predicted the cross-validated (10-fold) data with an accuracy of upto 71%. Moving average analysis resulted in single index based models with an accuracy upto 80%.

Diphenhydramine abuse and detoxification: a brief review and case report.

Many medicines available over the counter from pharmacies are known to have abuse potential, including diphenhydramine (DPH), an antihistamine with antimuscarinic properties used for the treatment of insomnia. We present a brief review of the literature describing DPH abuse, and report the case of GF, a 56 year old woman who was admitted to an inpatient addictions unit for detoxification from DPH. A literature search revealed five case reports of DPH abuse including a total of six patients, published between 1986 and 2001. All reported cases exhibited features of DSM-IV criteria for substance dependence, and there was an apparent link with antipsychotic usage. GF was treated with antipsychotics, and was using up to thirty 50 mg DPH tablets each day. She described feeling 'good and calm' and 'it stopped the tremors'. GF tolerated a gradual dose reduction schedule, and completed the detoxification programme relatively comfortably. She was discharged from the inpatient detoxification unit as planned, and had not relapsed at six months. The described case report highlights the importance of enquiring about non prescribed medication when taking a drug history. Similarly community pharmacists and GPs should be vigilant to excessive requests for DPH, particularly in patients with a psychotic illness.