Histamine-2 (H2 ) antagonists can be safely removed from standard paclitaxel premedication regimens.

AIMS: The aim of this study is to investigate the rates of hypersensitivity reactions (HSRs) in patients receiving paclitaxel chemotherapy, with and without a histamine-2 (H2 ) antagonists. METHOD: This prospective, multi-centre, cohort study compared patients receiving paclitaxel treated with premedication regimens containing chlorphenamine, dexamethasone and an H2 antagonist vs patients treated without an H2 antagonist. Rates of HSRs were described and logistic multivariable regression was used to investigate any associations with H2 antagonist treatment, adjusting for confounding variables. RESULTS: A total of 1043 individuals were included in the study; of these, 638 (61%) patients received an H2 antagonist and 405 (49%) were not given an H2 antagonist. Incidence of HSR in the cohort treated with H2 antagonists was 11.31% (n = 70) vs 9.86% (n = 41) in the cohort without. There was no statistically significant difference between the rates of HSR observed in those receiving and not receiving an H2 antagonist (odds ratio 1.04, 95% CI 0.65, 1.66, P = .9). CONCLUSIONS: Results presented within the study are consistent with other recently published evidence to suggest that H2 antagonists do not confer any advantage as part of premedication regimens in reducing the incidence of HSR in patients treated with paclitaxel.

The Role of Cetirizine in the Changing Landscape of IV Antihistamines: A Narrative Review.

Since 1955, the only available H1 antihistamines for intravenous administration have been first-generation formulations and, of those, only intravenously administered (IV) diphenhydramine is still approved in the USA. Orally administered cetirizine hydrochloride, a second-generation H1 antihistamine, has been safely used over-the-counter for many years. In 2019, IV cetirizine was approved for the treatment of acute urticaria. In light of this approval, this narrative review discusses the changing landscape of IV antihistamines for the treatment of histamine-mediated conditions. Specifically, IV antihistamines will be discussed as a treatment option for acute urticaria and angioedema, as premedication to prevent infusion reactions related to anticancer agents and other biologics, and as an adjunct treatment for anaphylaxis and other allergic reactions. Before the development of IV cetirizine, randomized controlled trials of IV antihistamines for these indications were lacking. Three randomized controlled trials have been conducted with IV cetirizine versus IV diphenhydramine in the ambulatory care setting. A phase 3 trial of IV cetirizine 10 mg versus IV diphenhydramine 50 mg was conducted in 262 adults who presented to the urgent care/emergency department with acute urticaria requiring antihistamines. For the primary efficacy endpoint, defined as change from baseline in a 2-h patient-rated pruritus score, non-inferiority of IV cetirizine to IV diphenhydramine was demonstrated (score - 1.6 vs - 1.5, respectively; 95% CI - 0.1, 0.3). Compared with IV diphenhydramine, IV cetirizine demonstrated fewer adverse effects including less sedation, a significantly shorter length of stay in the treatment center, and fewer returns to the treatment center at 24 and 48 h. Similar findings were demonstrated in another phase 2 acute urticaria trial and in a phase 2 trial assessing IV cetirizine for pretreatment for infusion reactions in the oncology/immunology setting. IV cetirizine is associated with similar patient outcomes, fewer adverse effects, and increased treatment center efficiency than IV diphenhydramine.

Antihistamine-related deaths in England: Are the high safety profiles of antihistamines leading to their unsafe use?

AIMS: Antihistamines are routinely taken to control allergic reactions or sedation to induce sleep. There are, however, growing concerns regarding sedating antihistamine misuse. This research aims to evaluate deaths related to antihistamines in England occurring during 2000-2019. METHODS: Cases reported to the National Programme on Substance Abuse Deaths from England occurring in 2000-2019 with antihistamine detections at postmortem were extracted for analysis. RESULTS: In total, 1666 antihistamine postmortem detections were identified from 1537 cases. Sedating antihistamines available for purchase under pharmacist supervision but without need for a prescription (pharmacy-only medications) were present in a significant majority of cases (85.2%, P < .01). Despite an increasing trend for antihistamine-related deaths over time, the proportion of deaths where an antihistamine was implicated declined over the same period. Specific concerns with regards to the misuse of these pharmacy-only sedating antihistamines are raised with regards to the significant proportion of cases that were concluded as suicide (20.9%, P < .01), and the high prevalence of their use in combination with other central nervous system depressants (94.8% of cases). CONCLUSION: This is the first report in over 40 years regarding antihistamine-related mortality from England. The rising trend in sedating antihistamine-related deaths may be contributed to by their increasing availability and the perceived negligible dangers associated with antihistamines, both from the general public and learned professionals. Awareness of the dangerous sedative properties that some antihistamines possess is, however, heightened in individuals deliberately seeking these effects. Urgent review of sedating antihistamines currently assigned under the pharmacy-only classification is needed to achieve antihistamine harm reduction.

Ultraviolet A photosensitivity profile of dexchlorpheniramine maleate and promethazine-based creams: Anti-inflammatory, antihistaminic, and skin barrier protection properties.

BACKGROUND: Unwanted side effects such as dryness, hypersensitivity, and cutaneous photosensitivity are challenge for adherence and therapeutical success for patients using treatments for inflammatory and allergic skin response. AIMS: In this study, we compared the effects of two dermatological formulations, which are used in inflammatory and/or allergic skin conditions: dexchlorpheniramine maleate (DCP; 10 mg/g) and promethazine (PTZ; 20 mg/g). METHODS: We evaluated both formulations for phototoxicity potential, skin irritation, anti-inflammatory and antihistaminic abilities, and skin barrier repair in vitro and ex vivo using the standard OECD test guideline n° 432, the ECVAM protocol n° 78, and cultured skin explants from a healthy patient. Ultraviolet A was chosen as exogenous agent to induce allergic and inflammatory response. RESULTS: Both PTZ and DCP promoted increases in interleukin-1 (IL-1) synthesis in response to ultraviolet A (UVA) radiation compared to control. However, the increase observed with PTZ was significantly greater than the DCP, indicating that the latter has a lower irritant potential. DCP also demonstrated a protective effect on UVA-induced leukotriene B4 and nuclear factor kappa B (NF-κB) synthesis. Conversely, PTZ demonstrates more robust UVA antihistaminic activity. Likewise, PTZ promoted a significantly greater increase in the production of involucrin and keratin 14, both associated with protective skin barrier property. CONCLUSION: In conclusion, these data suggest possible diverging UVA response mechanisms of DCP and PTZ, which gives greater insight into the contrasting photosensitizing potential between DCP and PTZ observed in the patients.

Histamine Receptor H1-Mediated Sensitization of TRPV1 Mediates Visceral Hypersensitivity and Symptoms in Patients With Irritable Bowel Syndrome.

BACKGROUND & AIMS: Histamine sensitizes the nociceptor transient reporter potential channel V1 (TRPV1) and has been shown to contribute to visceral hypersensitivity in animals. We investigated the role of TRPV1 in irritable bowel syndrome (IBS) and evaluated if an antagonist of histamine receptor H1 (HRH1) could reduce symptoms of patients in a randomized placebo-controlled trial. METHODS: By using live calcium imaging, we compared activation of submucosal neurons by the TRPV1 agonist capsaicin in rectal biopsy specimens collected from 9 patients with IBS (ROME 3 criteria) and 15 healthy subjects. The sensitization of TRPV1 by histamine, its metabolite imidazole acetaldehyde, and supernatants from biopsy specimens was assessed by calcium imaging of mouse dorsal root ganglion neurons. We then performed a double-blind trial of patients with IBS (mean age, 31 y; range, 18-65 y; 34 female). After a 2-week run-in period, subjects were assigned randomly to groups given either the HRH1 antagonist ebastine (20 mg/day; n = 28) or placebo (n = 27) for 12 weeks. Rectal biopsy specimens were collected, barostat studies were performed, and symptoms were assessed (using the validated gastrointestinal symptom rating scale) before and after the 12-week period. Patients were followed up for an additional 2 weeks. Abdominal pain, symptom relief, and health-related quality of life were assessed on a weekly basis. The primary end point of the study was the effect of ebastine on the symptom score evoked by rectal distension. RESULTS: TRPV1 responses of submucosal neurons from patients with IBS were potentiated compared with those of healthy volunteers. Moreover, TRPV1 responses of submucosal neurons from healthy volunteers could be potentiated by their pre-incubation with histamine; this effect was blocked by the HRH1 antagonist pyrilamine. Supernatants from rectal biopsy specimens from patients with IBS, but not from the healthy volunteers, sensitized TRPV1 in mouse nociceptive dorsal root ganglion neurons via HRH1; this effect could be reproduced by histamine and imidazole acetaldehyde. Compared with subjects given placebo, those given ebastine had reduced visceral hypersensitivity, increased symptom relief (ebastine 46% vs placebo 13%; P = .024), and reduced abdominal pain scores (ebastine 39 ± 23 vs placebo 62 ± 22; P = .0004). CONCLUSIONS: In studies of rectal biopsy specimens from patients, we found that HRH1-mediated sensitization of TRPV1 is involved in IBS. Ebastine, an antagonist of HRH1, reduced visceral hypersensitivity, symptoms, and abdominal pain in patients with IBS. Inhibitors of this pathway might be developed as a new treatment approach for IBS. ClinicalTrials.gov no: NCT01144832.

Levocetirizine and rupatadine in chronic idiopathic urticaria.

BACKGROUND: Chronic idiopathic urticaria (CIU) is a common dermatological condition. Its pathogenesis involves mainly histamine and also other mediators, including platelet-activating factor (PAF) and tumor necrosis factor-α (TNF-α). In the absence of an exact etiology, H1 -antihistaminics are the mainstay of treatment. Levocetirizine is widely prescribed for CIU. Rupatadine, a newer antihistaminic, has PAF receptor antagonist activity and has shown anti-TNF-α activity in vitro. These additional anti-inflammatory effects may improve its efficacy. OBJECTIVES: This study was conducted to compare the efficacy and safety of rupatadine and levocetirizine, respectively, in CIU patients. METHODS: A prospective, open, comparative, randomized study was conducted in 100 patients, of whom 50 were treated with levocetirizine and 50 were treated with rupatadine. Efficacy parameters used were urticarial activity score (UAS) and Dermatology Life Quality Index (DLQI) values. Safety was evaluated by monitoring for adverse drug reactions and by using the critical flicker fusion threshold (CFFT) test and a visual analog scale (VAS) at baseline, and at 2, 4, and 6 weeks. RESULTS: The mean UAS decreased to 0.10 in the levocetirizine group and to 0.38 in the rupatadine group. Patients in the levocetirizine group showed a more significant (P < 0.001) improvement, although symptoms improved in both groups. Significant reductions in mean DLQI scores were observed in both groups, but the decrease was statistically significant in the levocetirizine group (P < 0.05). Somnolence was the most common side effect in both groups. Patients in the levocetirizine group showed more psychomotor impairment based on the CFFT test. Findings on the VAS showed sedative effects in both groups (P < 0.05). CONCLUSIONS: Levocetirizine was found to be more efficacious than rupatadine in CIU patients, but both drugs caused mild sedation.

Acute hepatitis after starting pinaverium bromide in a patient taking mirtazapine.

A 56-year-old man presented with chronic abdominal pain. He had been evaluated extensively in the recent past undergoing upper gastrointestinal endoscopy, colonoscopy and CT scan of the abdomen with normal results. The provisional diagnosis of irritable bowel syndrome was performed and pinaverium bromide was started. The patient had pre-existing hypertension, a major depressive disorder and gastro-oesophageal reflux disease. He had been taking nebivolol and pantoprazole for several years and mirtazapine for the last 1 year. The patient developed nausea, vomiting and anorexia after 5 days of starting pinaverium bromide. Investigations revealed marked elevation of liver enzymes and bilirubin. He was negative for HIV, HBSAg, anti-hepatitis C virus, IgM for hepatitis A virus, hepatitis E virus, antinuclear antibody and antimitochondrial antibody. An ultrasound showed mild hepatomegaly with hypoechoic echo texture; the rest of scan was normal. Pinaverium and mirtazapine were stopped immediately. The patient was treated symptomatically and his liver profile returned to normal after 4 weeks.

Effect of azelastine on cardiac repolarization of guinea-pig cardiomyocytes, hERG K⁺ channel, and human L-type and T-type Ca²âº channel.

Azelastine is a second generation histamine H1-receptor antagonist used as an anti-asthmatic and anti-allergic drug that can induce QT prolongation and torsades de pointes. We investigated the acute effects of azelastine on human ether-a-go-go-related gene (hERG) channels, action potential duration (APD), and L-type (I(Ca,L)) and T-type Ca²âº current (I(Ca,T)) to determine the electrophysiological basis for its proarrhythmic potential. Azelastine increased the APD at 90% of repolarization concentration dependently, with an IC50 of 1.08 nM in guinea-pig ventricular myocytes. We examined the effects of azelastine on the hERG channels expressed in Xenopus oocytes and HEK293 cells using two-microelectrode voltage-clamp and patch-clamp techniques. Azelastine induced a concentration-dependent decrease of the hERG current amplitude at the end of the voltage steps and tail currents. The IC50 for the azelastine-induced block of the hERG currents expressed in HEK293 cells was 11.43 nM, while the drug inhibited I(Ca,L) and I(Ca,T) with IC50 values of 7.60 and 26.21 µM, respectively. The S6 domain mutations, Y652A partially attenuated and F656A abolished hERG current block. These results suggest that azelastine is a potent blocker of hERG channels rather than I(Ca,L) or I(Ca,T), providing molecular mechanisms for the arrhythmogenic side effects during the clinical administration of azelastine.

A case of mannitol hypersensitivity.

Mannitol is used for increased intracranial pressure and prevention of nephrotoxicity. We present a case report of a patient who experienced an anaphylactic response to mannitol and review the literature.

Cheese: an old drug in a new wrapper.

BACKGROUND: An unexpected outbreak of "cheese" heroin, which contained diphenhydramine and usually acetaminophen, began in Dallas around 2004. Onset occurred among youths living in neighborhoods populated by first-generation Hispanic immigrants. Little was known about the problem or the social strengths and deficits of these youth, who were primarily inhalers ("snorters") but at risk of transitioning to injection. METHODS: Multiple data sources were used, including surveys, data from emergency departments, law enforcement, treatment programs, and coroner, and interviews with users and key informants. RESULTS: Among heroin users under age 20, overdose deaths peaked in 2006, the school survey responses to using "cheese" heroin peaked in 2007, and treatment admissions peaked in 2008. Hispanic youth entering treatment were less likely to be injectors and report fewer problems than their Anglo counterparts and they were more likely to live with their families and to be supported by them. Sixty percent of the Hispanic youth had been in treatment previously and only 53% completed treatment. Cocaine and/or benzodiazepines were involved in 32% of the adolescent heroin deaths. CONCLUSIONS: The timely use of multiple data sources enabled this outbreak to be quickly identified and monitored, and the Cheese Heroin Task Force used the collected data to help respond to the problem, although retention in treatment and readmissions remained problematic. Cultural problems including immigration status, language, and misunderstandings about the nature of treatment were barriers to successful treatment outcomes. Completion of treatment as an inhaler is critical to reducing the likelihood of transitioning to injection.

Mirtazapine and mefloquine therapy for progressive multifocal leukoencephalopathy in a patient infected with human immunodeficiency virus.

PURPOSE: A case of progressive multifocal leukoencephalopathy (PML) in a patient infected with human immunodeficiency virus (HIV) treated with mirtazapine and mefloquine is reported. SUMMARY: A 49-year-old African-American man who was recently diagnosed with HIV infection was admitted to the hospital for progressive ataxia, dysarthria, and unsteady gait. Upon initial examination, the patient was fully oriented but appeared drowsy and uncooperative and was observed to be unsteady on his feet. Magnetic resonance imaging of the patient's brain revealed marked cerebellar and mild cerebral atrophy and moderate, nonspecific white matter disease. The results of a lumbar puncture revealed the presence of JC virus, and PML was diagnosed. As the patient's cognitive function began to worsen, mirtazapine and mefloquine were initiated. Treatment with mirtazapine 30 mg orally daily and mefloquine hydrochloride 250 mg orally for three days, then 250 mg weekly, was initiated. The dosing regimen was derived from a study currently underway at Washington University in St. Louis, Missouri. The patient also had pneumonia and, on day 7 of hospitalization, required intubation. The patient was extubated on day 11 and showed significant cognitive improvement; he was able to communicate his wish to enact a "Do Not Intubate" order. At this time, the patient began refusing all medications and ultimately died on hospital day 16 due to respiratory failure. CONCLUSION: A patient with HIV infection and PML was treated with mirtazapine and mefloquine. He tolerated the drugs well and exhibited functional and cognitive improvement, but the specific effects of mirtazapine and mefloquine were difficult to discern.

Essential oil from Citrus aurantifolia prevents ketotifen-induced weight-gain in mice.

Obesity is a major health problem world-wide. Medical intervention is often needed to tackle this problem, and accordingly the need for developing more effective, safer and cheaper weight reducing drugs has become paramount in recent years. In the present study, the effects of lime (Citrus aurantifolia) essential oils in reducing body weight, individually and in co-administration with ketotifen, an antihistaminic drug that causes weight gain, has been investigated using a mouse model. During the 45 days experimental period, the mice that received ketotifen demonstrated an enhancement both in the amount of food intake and body weight compared with the control group. Groups treated with lime essential oil displayed a reduction in body weight and food consumption in mice, possibly through promoting anorexia which might have played a role in weight loss. Interestingly, co-administration of the lime essential oil and ketotifen caused significant suppression in gaining weight, as well as decreased body weights of mice. The data obtained in this study suggested that lime essential oil plays an important role in weight loss and could be useful in the treatment of drug-induced obesity and related diseases. The GC-MS analysis of the essential oils of C. aurantifolia was also performed and approximately 22 main components, with limonene (28.27%) being the principal one, were identified and quantified.

Revisão sobre a efícacia e segurança dos anti-histamínicos de primeira e segunda geração / Revision on efficacy and safety of antihistamines of first and second generation

Objetivo: Revisar a eficácia e segurança dos principais anti-histamínicos de primeira e segunda geração. Os anti-histamínicos correspondem a um grupo extenso de medicamentos que vêm apresentando grandes avanços no conhecimento de suas ações e estão entre os agentes mais utilizados na prática clínica em diversas doenças alérgicas. Método: Levantamento bibliográfico nos bancos de dados PubMed, Medline, LILACS, SCIELO e capítulos de livros nos últimos 10 anos, sendo incluídos artigos históricos. Resultados: Nessa revisão são destacadas as principais características da histamina, as diferenças entre os receptores de histamina, o desenvolvimento dos anti-histamínicos de primeira e segunda geração, sua classificação e os principais efeitos colaterais de cada grupo de anti-histamínicos. Conclusão: A presente revisão não pretende esgotar o assunto sobre eficácia e segurança dos anti-histamínicos, mas destaca a falta de estudos bem conduzidos sobre eficácia dos anti-histamínicos de primeira geração e o número crescente de metanálises sobre farmacodinâmica, potência, eficácia e segurança dos anti-histamínicos de segunda geração.

Objective: To review the efficacy and safety of the main antihistamines of first and second generation. The antihistamines represent an extensive group of drugs that are showing great advances in knowledge of their actions and are among the most common agents used in clinical practice in various allergic diseases. Method: Searches in PubMed, Medline, LILACS, SCIELO database and book chapters in the last 10 years, including historic articles. Results: This review highlights the main features of histamine, the differences between histamine receptors, development of first and second generation antihistamines, their classification, and the main side effects of each group of antihistamines. Conclusion: The present review is not intended to exhaust the subject on efficacy and safety of antihistamine, but it highlights the lack of well conducted studies of the efficacy of first-generation antihistamine and the rising number of meta-analysis of pharmacodynamics, potency, efficacy and safety of second-generation antihistamines.

Gender and interindividual variability in pharmacokinetics.

Like any other drugs, antiallergic medications can be associated with large inter- and intraindividual variability in their disposition. The best-documented examples belong to the H1 antihistamines. Variable drugs are more likely to show unpredictable therapeutic response with both increased risks of side effects and subtherapeutic dosing in individual subjects. This article will review the main factors contributing to intervariability in pharmacokinetics with a special emphasis on gender differences, genetic polymorphism, and food habits.

Hydroxyzine, a first generation H(1)-receptor antagonist, inhibits human ether-a-go-go-related gene (HERG) current and causes syncope in a patient with the HERG mutation.

QT prolongation, a risk factor for arrhythmias, can result from genetic variants in one (or more) of the genes governing cardiac repolarization as well as intake of drugs known to affect a cardiac K(+) channel encoded by human ether-a-go-go-related gene (HERG). In this paper, we will report a case of drug-induced long QT syndrome associated with an H(1)-receptor antagonist, hydroxyzine, in which a mutation was identified in the HERG gene. After taking 75 mg of hydroxyzine for several days, a 34-year-old female began to experience repetitive syncope. The deleterious effect of hydroxyzine was suspected because QTc interval shortened from 630 to 464 ms after cessation of the drug. Later on, the patient was found to harbor an A614V-HERG mutation. By using the patch-clamp technique in the heterologous expression system, we examined the functional outcome of the A614V mutation and confirmed a dominant-negative effect on HERG expression. Hydroxyzine concentration-dependently inhibited both wild-type (WT) and WT/A614V-HERG K(+) currents. Half-maximum block concentrations of WT and WT/A614V-HERG K(+) currents were 0.62 and 0.52 microM, respectively. Thus, accidental combination of genetic mutation and intake of hydroxyzine appeared to have led to a severe phenotype, probably, syncope due to torsade de pointes.

Prophylactic mirtazapine reduces intrathecal morphine-induced pruritus.

BACKGROUND: Activation of the serotonergic system is an important factor in the pathogenesis of intrathecal morphine-induced pruritus. Mirtazapine is a new antidepressant that selectively blocks 5-HT(2) and 5-HT(3) receptors. We therefore tested the hypothesis that preoperative mirtazapine would reduce the incidence of intrathecal morphine-induced pruritus. METHODS: One hundred and ten ASA I patients undergoing lower limb surgery under spinal anaesthesia were randomly allocated into two equal groups and received either mirtazapine 30 mg or an orally disintegrating placebo tablet 1 h before operation in a prospective, double-blinded trial. All patients received an intrathecal injection of 15 mg of 0.5% isobaric bupivacaine and 0.2 mg preservative-free morphine. The occurrence and the severity of pruritus were assessed at 3, 6, 9, 12, and 24 h after intrathecal morphine. RESULTS: Pruritus was significantly more frequent in the placebo group compared with the mirtazapine group (75% vs 52%, respectively; P=0.0245). The time to onset of pruritus in the two groups was also significantly different. The patients who experienced pruritus in the placebo group had a faster onset time than that in the mirtazapine group [mean (sd): 3.2 (0.8) vs 7.2 (4.1) h, P<0.0001]. CONCLUSIONS: Mirtazapine premedication prevents pruritus induced by intrathecal morphine in patients undergoing lower limb surgery with spinal anaesthesia.

[The investigation of efficacy and safety of Aerius to seasonal allergic rhinitis].

OBJECTIVE: To evaluate the efficacy and safety of Aerius to seasonal allergic rhinitis. METHOD: Using randomized, controlled method, treatment group 40 cases, oral administration Aerius 5 mg/d for 12 days; control group 35 cases, oral administration Aerius 5 mg/d for 12 days, investigating their efficacy and safety. RESULT: The total effective rate of treatment group was 92.50%, while control group was 85.71%, there was significant difference between them (P<0.05). Significant improvements of seasonal allergic rhinitis nasal obstruction were seen in treatment group after using Aerius (P<0.05). The incidence of side effect of treatment group was 2.50%. CONCLUSION: Aerius is safe and can effectively reduction in nasal and nonnasal symptoms in patients with seasonal allergic rhinitis.

Cardiotoxic effects of antihistamines: from basics to clinics (...and back).

Drug-induced arrhythmias, particularly those caused by a prolonged QT interval, have become a critical safety issue for compound selection during development by pharmaceutical companies and for health care regulators. The last two decades have witnessed enormous progress in the definition of the clinical conditions that facilitate the occurrence of such serious adverse effects, of its molecular basis, and in the preclinical strategies aimed at early identification of the cardiotoxic liability of compounds undergoing investigation or already used in the clinic. Moreover, despite the fact that acquired factors play an obvious role in drug-induced arrhythmias, it has become evident that the disease is often manifested upon the interaction of strong environmental stressors with specific genetic determinants of the affected individuals; in that sense, few examples can illustrate the existing interaction between acquired and genetic factors in disease manifestation better than drug-induced arrhythmogenesis. Progress in this field has been mainly driven by a strong interaction among various disciplines, including medicinal chemistry, pharmacology, electrophysiology, molecular genetics, and clinical cardiology; such an interdisciplinary approach has often generated unexpected discoveries of great clinical value, allowing clinicians to drive drug selection toward compounds of proven efficacy and safety. Historically, studies on antihistamines have paved the way for much of our current understanding of the mechanisms and problems associated with QT prolongation and drug-induced arrhythmogenesis; therefore, in this perspective, we will attempt to summarize how basic research studies have helped the interpretation of clinically relevant phenomena (from basics to clinics...) and how this information has prompted new emphasis in preclinical studies aimed at predicting the cardiotoxic potential of compounds (...and back). The current availability of several strategies provided with great predictive potential, together with an increased awareness of physicians, pharmaceutical industries, and health care regulators to this potentially serious cardiovascular side effect, has significantly decreased the risk associated with drug-induced arrhythmias caused by drugs newly introduced into the market; nevertheless, given the large number of cases of QT prolongation still occurring during treatment with a wide variety of congeners, it seems appropriate to review the issue of the cardiotoxic actions of antihistamines, as a better comprehension of the underlying mechanisms and risk factors is likely to contribute to the improvement of the risk/benefit ratio for pharmacological treatment in several therapeutic areas.