A randomized study of IV prochlorperazine plus diphenhydramine versus IV hydromorphone for migraine-associated symptoms: A post hoc analysis.

OBJECTIVE: We conducted a randomized trial among emergency department patients with migraine to determine the relative impact on migraine-associated symptoms of hydromorphone, an opioid, versus prochlorperazine, an antidopaminergic antiemetic. METHODS: This was a post hoc analysis of data from a double-blind study registered at http://clinicaltrials.gov (NCT02389829). Patients who met International Classification of Headache Disorders, 3rd edition criteria for migraine without aura or for probable migraine without aura were eligible for participation. Participants received either hydromorphone 1 mg IV or prochlorperazine 10 mg IV plus diphenhydramine 25 mg IV and could receive a second dose of the same medication 1 h later if needed. The outcomes were sustained relief of nausea, photophobia, and phonophobia. RESULTS: A total of 127 patients were enrolled, of whom 63 received prochlorperazine and 64 received hydromorphone. Of 49 patients in the prochlorperazine arm who reported nausea at baseline, 34 (69.4%) reported complete resolution without relapse versus 15/49 (30.6%) in the hydromorphone arm (absolute risk reduction [ARR] = 38.8%, 95% CI: 20.5%-57.0%, p < 0.001). Of 55 patients in the prochlorperazine arm who reported photophobia at baseline, 23 (41.8%) reported complete resolution without relapse versus 13/62 (20.9%) patients treated with hydromorphone (ARR = 20.8%, 95% CI: 4.3%-37.3%, p = 0.014). Of 56 patients in the prochlorperazine arm who reported phonophobia at baseline, 25 (44.6%) reported complete resolution without relapse versus 16/59 (27.1%) in the hydromorphone arm (ARR = 17.5%, 95% CI: 0.3%-34.8%, p = 0.049). For adverse events, three patients in the prochlorperazine arm reported anxiety or restlessness, and nine patients in the hydromorphone arm reported dizziness or weakness. CONCLUSIONS: Prochlorperazine plus diphenhydramine is more efficacious than hydromorphone for the treatment of migraine-associated symptoms.

Effectiveness of Standard Combination Therapy in Pediatric Migraine.

BACKGROUND: A combination of parenteral medications (often referred to as standard combination therapy) is frequently used in the treatment of acute migraine in the pediatric emergency department (PED). The primary aim of this study was to evaluate the two-hour, 24-hour, and seven-day impact of one such regimen on pain in children who present to the PED. Standard combination therapy for purposes of our study is defined as a bolus of intravenous saline, and a combination of intravenous ketorolac, prochlorperazine, and diphenhydramine. METHODS: This prospective observational study included 120 children between the ages seven and 18 years who presented to the PED with migraine, whose parents could read and understand the consent form in English, and who were treated with standard combination therapy. The primary outcome measure for this study was the change in severity of pain as noted by the child using the Faces Pain Scale-Revised. We analyzed normally distributed continuous variables by mean and standard deviation, whereas non-normally distributed continuous variables are reported by median and interquartile range. RESULTS: Nonparametric Friedman testing on the entire cohort (n = 120) noted that there was a statistically significant change in the Faces pain scale from before administration of standard combination therapy to the two-hour, 24-hour, and one-week time point with a reduction in pain score of 87.5%, 100%, and 50%, respectively, at the three time points. CONCLUSIONS: This study noted moderate relief of pain after administration of standard combination therapy, which persisted at one-week after administration.

Antiviral activity of chlorpromazine, fluphenazine, perphenazine, prochlorperazine, and thioridazine towards RNA-viruses. A review.

In 2020 the whole world focused on antivirus drugs towards SARS-CoV-2. Most of the researchers focused on drugs used in other viral infections or malaria. We have not seen such mobilization towards one topic in this century. The whole situation makes clear that progress needs to be made in antiviral drug development. The first step to do it is to characterize the potential antiviral activity of new or already existed drugs on the market. Phenothiazines are antipsychotic agents used previously as antiseptics, anthelminthics, and antimalarials. Up to date, they are tested for a number of other disorders including the broad spectrum of viruses. The goal of this paper was to summarize the current literature on activity toward RNA-viruses of such drugs like chlorpromazine, fluphenazine, perphenazine, prochlorperazine, and thioridazine. We identified 49 papers, where the use of the phenothiazines for 23 viruses from different families were tested. Chlorpromazine, fluphenazine, perphenazine, prochlorperazine, and thioridazine possess anti-viral activity towards different types of viruses. These drugs inhibit clathrin-dependent endocytosis, cell-cell fusion, infection, replication of the virus, decrease viral invasion as well as suppress entry into the host cells. Additionally, since the drugs display activity at nontoxic concentrations they have therapeutic potential for some viruses, still, further research on animal and human subjects are needed in this field to verify cell base research.

Endocytosis Inhibition in Humans to Improve Responses to ADCC-Mediating Antibodies.

A safe and controlled manipulation of endocytosis in vivo may have disruptive therapeutic potential. Here, we demonstrate that the anti-emetic/anti-psychotic prochlorperazine can be repurposed to reversibly inhibit the in vivo endocytosis of membrane proteins targeted by therapeutic monoclonal antibodies, as directly demonstrated by our human tumor ex vivo assay. Temporary endocytosis inhibition results in enhanced target availability and improved efficiency of natural killer cell-mediated antibody-dependent cellular cytotoxicity (ADCC), a mediator of clinical responses induced by IgG1 antibodies, demonstrated here for cetuximab, trastuzumab, and avelumab. Extensive analysis of downstream signaling pathways ruled out on-target toxicities. By overcoming the heterogeneity of drug target availability that frequently characterizes poorly responsive or resistant tumors, clinical application of reversible endocytosis inhibition may considerably improve the clinical benefit of ADCC-mediating therapeutic antibodies.

Antimelanoma activity of perphenazine and prochlorperazine in human COLO829 and C32 cell lines.

Cutaneous melanoma is least common (only about 1% of skin cancers) but is the deadliest malignant tumor. Moreover, amelanotic types of melanoma are very difficult for clinical diagnosis. The standard therapy can cause a lot of side effects, e.g., nausea, vomiting, and headaches, which means that novel and effective strategies are required. Interestingly, phenothiazine derivatives possess sedative, antiemetic, and anticancer activity. Our goal was to determine the effect of perphenazine and prochlorperazine on cell viability, motility, microphthalmia-associated transcription factor (MITF) and tyrosinase content in melanotic and amelanotic melanoma cells. The viability of C32 and COLO829 melanoma cells was evaluated by the WST-1 colorimetric assay; impact on motility of human melanoma was performed by wound-healing assay, while tyrosinase and MITF content were determined by Western blot. In the present study, we explore the anticancer effect of perphenazine and prochlorperazine in human melanotic (COLO829) and amelanotic (C32) melanoma cells concluding that prochlorperazine inhibits cell viability in a concentration-dependent manner, impairs motility, and decreases tyrosinase and MITF amounts. Moreover, the analyzed drugs decrease/increase MITF amount depending on the type of melanoma. We demonstrated that the decrease of MITF and tyrosinase protein induces motility inhibition of C32 cells, which suggests the ability of those drugs to restore cancer cell sensitivity to treatment. The ability of prochlorperazine to contain the spread of the amelanotic melanoma in vivo may be helpful in the development of a new and effective antimelanoma therapies.

Characterization of binding of antipsychotics to muscarinic receptors using mouse cerebral cortex.

Antipsychotics are often the first-line treatment for behavioral and psychological symptoms of dementia. However, the potential anticholinergic effects of antipsychotics could counteract the therapeutic effects of cholinesterase inhibitors used to treat dementia. We investigated the inhibitory effects of 26 antipsychotics on [N-Methyl-3H]scopolamine specific binding in mouse cerebral cortex. At 10-5 M, chlorpromazine, levomepromazine, prochlorperazine, timiperone, zotepine, pimozide, blonanserin, olanzapine, quetiapine, and clozapine inhibited [N-Methyl-3H]scopolamine binding by > 45%. Furthermore, the pKi values of chlorpromazine, levomepromazine, zotepine, olanzapine, and clozapine overlapped with their clinically achievable blood concentrations. Therefore, the anticholinergic properties of these antipsychotics could attenuate the effects of cholinesterase inhibitors.

Opioid-Induced "Likeability" and "Feeling Good" Are Not Associated With Return Visits to an ED Among Migraine Patients Administered IV Hydromorphone.

BACKGROUND: Parenteral opioids are used in more than 50% of emergency department (ED) visits for migraine. Use of opioids for migraine has been associated with subsequent ED visits, perhaps because of opioid-induced euphoria. In this study, we quantify the extent to which nontherapeutic effects of opioids influence migraine outcomes. We hypothesized that "feeling good" and medication likeability would in fact be associated with receipt of opioids (rather than relief of migraine pain) and that receipt of opioids (rather than relief of migraine pain) would be associated with return visits to the ED. METHODS: During an ED-based clinical trial, migraine patients were randomized to receive hydromorphone 1 mg or prochlorperazine 10 mg + diphenhydramine 25 mg IV. Thirty minutes after medication administration, we asked, (1) How much did you like the medication you received? and (2) How good did the medication make you feel? Participants were asked to provide answers on a 0-10 scale. We also determined 0-10 pain scores at baseline and 1 hour and number of return visits for headache during the subsequent month. RESULTS: Sixty-three patients received prochlorperazine and 64 hydromorphone. Prochlorperazine pain scores improved by 6.8 (SD: 2.6), hydromorphone by 4.7 (SD: 3.3) (95%CI for difference of 2.1: 1.0, 3.2). On the 0-10 likeability scale, prochlorperazine patients reported a mean of 7.2 (SD: 2.8), hydromorphone 6.9 (SD: 2.9) (95% CI for difference of 0.3: -0.7, 1.3). On the 0-10 feeling good scale, prochlorperazine patients reported a mean of 7.5 (SD: 2.3), hydromorphone 6.8 (SD: 2.8) (95%CI: for difference of 0.7: -0.2, 1.6). In the hydromorphone group, 8/57 (14%, 95%CI: 7, 26%) returned to the ED vs 5/63 (8%, 95%CI: 3,18%) in the prochlorperazine group. In regression modeling, feeling good was independently associated with pain relief (P < .01) but not with medication received (P = .67) or return visits (P = .12). Similarly, medication likeability was independently associated with pain relief (P < .01) but not medication received (P = .12) or return visits (P = .16). CONCLUSION: We did not detect an association between hydromorphone and medication likeability, feeling good, or return visits to the ED. Headache relief was associated with medication likeability and feeling good.

Perphenazine and prochlorperazine induce concentration-dependent loss in human glioblastoma cells viability.

Phenothiazine derivatives possess biological properties very useful for cancer therapy, such as antiemetic and sedative activity as well as good blood-brain barrier permeability. Our goal was to determine if perphenazine and prochlorperazine are possessing cytotoxic activity towards U87-MG cells. It has been shown that the analyzed drugs induce concentration-dependent loss in cell viability, what correlates with their chemical structure. The calculated EC50 values for perphenazine (0.98 µM) and prochlorperazine (0.97 µM) are related to their toxic concentrations in human plasma. The obtained results suggest that perphenazine and prochlorperazine may have a potential for the development of new and effective anticancer therapies.

Randomized study of IV prochlorperazine plus diphenhydramine vs IV hydromorphone for migraine.

OBJECTIVE: To determine outcomes among patients with migraine in the emergency department (ED) who receive IV hydromorphone vs IV prochlorperazine + diphenhydramine. METHODS: This study was conducted in 2 EDs in New York City. Patients who met international criteria for migraine were eligible for participation if they had not used an opioid within the previous month. Clinicians, participants, investigators, and research personnel were blinded to treatment. Patients were randomized in blocks of 4. Participants received hydromorphone 1 mg or prochlorperazine 10 mg + diphenhydramine 25 mg. Diphenhydramine was administered to prevent akathisia, a common side effect of IV prochlorperazine. The primary outcome was sustained headache relief, defined as achieving a headache level of mild or none within 2 hours of medication administration and maintaining that level for 48 hours without the requirement of rescue medication. A planned interim analysis was conducted once 48-hour data were available for 120 patients. RESULTS: The trial was halted by the data monitoring committee after 127 patients had been enrolled. The primary outcome was achieved in the prochlorperazine arm by 37 of 62 (60%) participants and in the hydromorphone arm by 20 of 64 (31%) participants (difference 28%, 95% confidence interval 12-45, number needed to treat 4, 95% confidence interval 2-9). CONCLUSIONS: IV hydromorphone is substantially less effective than IV prochlorperazine for the treatment of acute migraine in the ED and should not be used as first-line therapy. CLINICALTRIALSGOV IDENTIFIER: NCT02389829. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for patients in the ED with migraine, IV prochlorperazine + diphenhydramine is superior to IV hydromorphone.

Prochlorperazine Increases KCC2 Function and Reduces Spasticity after Spinal Cord Injury.

In mature neurons, low intracellular chloride level required for inhibition is maintained by the potassium-chloride cotransporter, KCC2. Impairment of Cl- extrusion after KCC2 dysfunction has been involved in many central nervous system disorders, such as seizures, neuropathic pain, or spasticity, after a spinal cord injury (SCI). This makes KCC2 an appealing drug target for restoring Cl- homeostasis and inhibition in pathological conditions. In the present study, we screen the Prestwick Chemical Library® and identify conventional antipsychotics phenothiazine derivatives as enhancers of KCC2 activity. Among them, prochlorperazine hyperpolarizes the Cl- equilibrium potential in motoneurons of neonatal rats and restores the reciprocal inhibition post-SCI. The compound alleviates spasticity in chronic adult SCI rats with an efficacy equivalent to the antispastic agent, baclofen, and rescues the SCI-induced downregulation of KCC2 in motoneurons below the lesion. These pre-clinical data support prochlorperazine for a new therapeutic indication in the treatment of spasticity post-SCI and neurological disorders involving a KCC2 dysfunction.

Prochlorperazine interaction with melanin and melanocytes.

Prochlorperazine is a phenothiazine-class antipsychotic drug usually used to treat nausea, vomiting and schizophrenia. Phenothiazine derivatives have been known to cause serious side effects, like extrapyramidal symptoms, but also skin disorders which mechanism has not been fully established. The aim of this study was to examine the interaction between prochlorperazine and melanin as well as to estimate the effect of prochlorperazine on cell viability, melanogenesis and antioxidant defense system in normal human melanocytes. We have demonstrated that prochlorperazine forms stable complexes with melanin, characterized by two classes of independent binding sites with the association constants K1∼106 M-1 and K2∼102 M-1. It has been shown that prochlorperazine induces concentration-dependent loss in cell viability. The value of EC50 was calculated to be 18.49 µM. Prochlorperazine in a concentration of 0.001 µM stimulated melanogenesis, while in concentrations 1.0 and 10.0 µM melanization process was inhibited. Furthermore, the drug in concentrations of 0.1, 1.0 and 10.0 µM caused changes in cellular antioxidant defense system, what indicated the induction of oxidative stress. The observed changes in cell viability, melanization and antioxidant defense system in normal human melanocytes after prochlorperazine treatment may explain a potential role of melanin, oxidative stress and melanocytes in mechanisms of undesirable side effects after accumulation of this drug in pigmented tissues.

Oligoantiemesis or Inadequate Prescription of Antiemetics in the Emergency Department: A Local and National Perspective.

BACKGROUND: Nausea and vomiting are common, but prevalence of antiemetic use in ED patients is unknown. OBJECTIVES: We determined the use of antiemetics in emergency department (ED) patients presenting with nausea and vomiting (NV). METHODS: We conducted a retrospective chart review of ED patients presenting to a local ED with NV and analyzed data from the National Hospital Ambulatory Care Survey for similar patients to determine the frequency of administration of antiemetics in the ED. RESULTS: Of 3876 patients presenting to a local ED with NV in 2014, 2637 (68% [95% confidence interval (CI) 67-69%]) received an antiemetic. Of an estimated 11.3 million U.S. ED visits for NV in 2011 (the latest year available), antiemetics were prescribed in 56% (95% CI 53-59%). Females, older patients, and those with vomiting were more likely to receive antiemetics. Use of antiemetics was associated with reduced admissions in the single institution (odds ratio [OR] 0.62, 95% CI 0.52-0.74), but not in the national database (OR 1.08, 95% CI 0.74-1.60). CONCLUSIONS: Many patients presenting with NV do not receive antiemetics while in the ED. Effort should be made to further study and reduce the phenomenon of undertreatment of nausea or vomiting, coined "oligoantiemesis."

Induction and antagonism of pica induced by teriparatide in rats.

Intermittent subcutaneous injection of teriparatide, an active fragment of human parathyroid hormone, is clinically used for the treatment of osteoporosis. Patients suffer from nausea, which is one of the side effects teriparatide induces; however, the etiology of teriparatide-induced nausea remains unknown. We have reported pica, kaolin ingestion behavior, can be used as an assessment of nausea-related response in rats. In this study, we investigated the characteristics of teriparatide-induced pica and the abilities of anti-emetic drugs to inhibit teriparatide-induced pica. Male and female adolescent (4-week-old), young (8-week-old), and adult (30-week-old) naive rats, and ovariectomized (OVX: 17-week-old) and sham-operated (17-week-old) rats subcutaneously received teriparatide (0.4 mg/kg, n=4), and their kaolin and food intakes were monitored for 24 h after the injection. Among the tested rats, we found that OVX rats, rather than male, female, and sham-operated rats, showed marked teriparatide-induced pica (0 mg/kg: 0.17±0.07 g, 0.4 mg/kg: 6.18±0.91 g). Teriparatide-induced pica in OVX rats was inhibited by intraperitoneal pretreatment with serotonin 5-HT3 (granisetron 0.5 mg/kg), dopamine D2 (prochlorperazine 0.5 mg/kg), neurokinin NK1 (fosaprepitant 1 mg/kg), and histamine H1 (diphenhydramine 10 mg/kg) receptor antagonists to 70%, 11%, 19%, and 59% of that in vehicle-treated control, respectively. These results suggest that teriparatide-induced pica in OVX rats has the potential to reflect teriparatide-induced nausea; 5-HT3, D2, NK1, and H1 receptor activation is involved in the development of this behavior; antagonists of these receptors have the potential to be medical candidates used as treatments for teriparatide-induced nausea in human patients.

Quantitative high throughput screening using a primary human three-dimensional organotypic culture predicts in vivo efficacy.

The tumour microenvironment contributes to cancer metastasis and drug resistance. However, most high throughput screening (HTS) assays for drug discovery use cancer cells grown in monolayers. Here we show that a multilayered culture containing primary human fibroblasts, mesothelial cells and extracellular matrix can be adapted into a reliable 384- and 1,536-multi-well HTS assay that reproduces the human ovarian cancer (OvCa) metastatic microenvironment. We validate the identified inhibitors in secondary in vitro and in vivo biological assays using three OvCa cell lines: HeyA8, SKOV3ip1 and Tyk-nu. The active compounds directly inhibit at least two of the three OvCa functions: adhesion, invasion and growth. In vivo, these compounds prevent OvCa adhesion, invasion and metastasis, and improve survival in mouse models. Collectively, these data indicate that a complex three-dimensional culture of the tumour microenvironment can be adapted for quantitative HTS and may improve the disease relevance of assays used for drug screening.

Repurposing of prochlorperazine for use against dengue virus infection.

The increasing prevalence of dengue virus (DENV) infection presents serious disease and economic burdens in countries where dengue epidemics are occurring. Despite the clinical importance, no DENV vaccine or anti-DENV drug is available. In this study, we found that prochlorperazine (PCZ), a dopamine D2 receptor (D2R) antagonist approved to treat nausea, vomiting, and headache in humans has potent in vitro and in vivo antiviral activity against DENV infection. PCZ can block DENV infection by targeting viral binding and viral entry through D2R- and clathrin-associated mechanisms, respectively. Administration of PCZ immediately or 6 hours after DENV infection in a Stat1-deficient mouse model completely protected against or delayed lethality. Overall, PCZ showed a previously unknown antiviral effect against DENV infection, and D2R may play a role in the DENV life cycle. Prophylactic and/or therapeutic treatment with PCZ might reduce viral replication and relieve the clinical symptoms of patients with dengue.

Combined drug therapy in the management of granulomatous amoebic encephalitis due to Acanthamoeba spp., and Balamuthia mandrillaris.

Granulomatous amoebic encephalitis (GAE) is caused by two protist pathogens, Acanthamoeba spp., and Balamuthia mandrillaris. Although rare, it almost always results in death. In the present study, amoebae were treated with various combinations of clinically-approved drugs, targeting vital cellular receptors and biochemical pathways. The results revealed that among the seven different combinations tested, three proved highly effective against both Acanthamoeba castellanii as well as B. mandrillaris at a concentration of 100µM. These combinations included (i) prochlorperazine plus loperamide; (ii) prochlorperazine plus apomorphine; and (iii) procyclidine plus loperamide. In viability assays, none of the drug-treated amoebae emerged as viable trophozoites, suggesting irreversible amoebicidal effects. Four combinations of drugs tested showed varied potency against A. castellanii and B. mandrillaris at 100µM. The combination of haloperidol and loperamide was highly effective against A. castellanii at 100µM, but potent effects against B. mandrillaris were observed only at 250µM. Digoxin and amlodipine were effective against A. castellanii and B. mandrillaris at 100µM and 250µM, respectively. In contrast, the combination of apomorphine and haloperidol was effective against B. mandrillaris and A. castellanii at 100µM and 250µM, respectively. At 100µM, the combination of procyclidine and amiodarone was effective against neither A. castellanii nor B. mandrillaris. In this case, amoebicidal properties were observed at 750µM for A. castellanii, and 950µM for B. mandrillaris. As these drugs are used clinically against non-communicable diseases, the findings reported here have the potential to be tested in a clinical setting against amoebic encephalitis caused by A. castellanii and B. mandrillaris.

Effects of prochlorperazine on normal vestibular ocular and perceptual responses: a randomised, double-blind, crossover, placebo-controlled study.

BACKGROUND: The present study investigated whether prochlorperazine affects vestibulo-ocular reflex (VOR) and vestibulo-perceptual function. METHODS: We studied 12 healthy naïve subjects 3 h after a single dose of oral prochlorperazine 5 mg in a randomised, placebo-controlled, double-blind, crossover study in healthy young subjects. Two rotational tests in yaw were used: (1) a threshold task investigating perceptual motion detection and nystagmic thresholds (acceleration steps of 0.5°/s(2)) and (2) suprathreshold responses to velocity steps of 90°/s in which vestibulo-ocular and vestibuloperceptual time constants of decay, as well as VOR gain, were measured. RESULTS: Prochlorperazine had no effect upon any measure of nystagmic or perceptual vestibular function compared to placebo. This lack of effects on vestibular-mediated motion perception suggests that the drug is likely to act more as an anti-emetic than as an antivertiginous agent.

Impact of genetic and non-genetic factors on clinical responses to prochlorperazine in oxycodone-treated cancer patients.

BACKGROUND: The contributions of DRD2 and OPRM1 genetic variants to clinical responses to prochlorperazine remain to be clarified in opioid-treated patients. We evaluated the clinical responses to prochlorperazine based on non-genetic and genetic factors in oxycodone-treated patients. METHODS: Seventy Japanese cancer patients starting oral prochlorperazine together with oxycodone were enrolled. Predose plasma prochlorperazine concentrations and serum prolactin concentrations were determined. The incidences of oxycodone-induced nausea and vomiting were monitored for 2weeks. RESULTS: Plasma prochlorperazine concentration and oxycodone daily dose were not associated with the incidences of nausea and vomiting. The incidence of nausea was significantly higher in the DRD2 TaqIA A1A2+A1A1 group than in the A2A2 group. The incidence of vomiting was significantly higher in females than in males. Before and after the prochlorperazine administration, the serum prolactin concentration was significantly higher in female patients than in male patients. The serum prolactin concentration was weakly correlated with prochlorperazine concentration and was significantly higher in the OPRM1 118AA group than in the AG+GG group. CONCLUSIONS: DRD2 TaqIA and female gender altered the prophylactic antiemetic efficacy of prochlorperazine. OPRM1 A118G together with plasma exposure of prochlorperazine and gender affected prolactin secretion in oxycodone-treated patients.

The phenothiazine-class antipsychotic drugs prochlorperazine and trifluoperazine are potent allosteric modulators of the human P2X7 receptor.

P2X7, an ATP-gated cation channel, is involved in immune cell activation, hyperalgesia and neuropathic pain. By regulating cytokine release in the brain, P2X7 has been linked to the pathophysiology of mood disorders and schizophrenia. We here assess the impact of 123 drugs that act in the central nervous system on human P2X7. Most prominently, the tricyclic antipsychotics prochlorperazine (PCP) and trifluoperazine (TFP) potently inhibited P2X7-mediated Ca2+ entry, dye permeation and ionic currents. In divalent cation-containing bath solutions or after prolonged incubation, ATP-evoked P2X7 currents were inhibited by 10 µM PCP. This effect was not related to dopamine receptor antagonism. Surprisingly, PCP co-applied with ATP enhanced inward currents in bath solutions with low divalent cation concentrations. Intracellular perfusion with PCP did not substitute for the extracellularly applied drug, indicating that its binding sites are accessible from the extracellular space. Since P2X7 current potentiation by PCP was voltage-dependent, at least one site may be located within the electrical field of the membrane. While the channel opening and closure kinetic was altered by PCP, the apparent affinity of ATP remained unchanged (potentiation) or changed slightly (inhibition). Measurements in human monocyte-derived macrophages confirmed the PCP-induced inhibition of ATP-evoked Ca2+ influx, Yo-Pro-1 permeability, and whole cell currents. Interestingly, neither heterologously expressed rat or mouse P2X7 nor native P2X7 in rat astrocyte cultures or in mouse bone marrow-derived macrophages were inhibited by perazines with a similar potency. We conclude that perazine-type neuroleptics are potent, but species-selective allosteric modulators of human but not murine P2X7 receptors.

In vitro efficacies of clinically available drugs against growth and viability of an Acanthamoeba castellanii keratitis isolate belonging to the T4 genotype.

The effects of clinically available drugs targeting muscarinic cholinergic, adrenergic, dopaminergic, and serotonergic receptors; intracellular calcium levels and/or the function of calcium-dependent biochemical pathways; ion channels; and cellular pumps were tested against a keratitis isolate of Acanthamoeba castellanii belonging to the T4 genotype. In vitro growth inhibition (amoebistatic) assays were performed by incubating A. castellanii with various concentrations of drugs in the growth medium for 48 h at 30°C. To determine amoebicidal effects, amoebae were incubated with drugs in phosphate-buffered saline for 24 h, and viability was determined using trypan blue exclusion staining. For controls, amoebae were incubated with the solvent alone. Of the eight drugs tested, amlodipine, prochlorperazine, and loperamide showed potent amoebicidal effects, as no viable trophozoites were observed (>95% kill rate), while amiodarone, procyclidine, digoxin, and apomorphine exhibited up to 50% amoebicidal effects. In contrast, haloperidol did not affect viability, but all the drugs tested inhibited A. castellanii growth. Importantly, amlodipine, prochlorperazine, and loperamide showed compelling cysticidal effects. The cysticidal effects were irreversible, as cysts treated with the aforementioned drugs did not reemerge as viable amoebae upon inoculation in the growth medium. Except for apomorphine and haloperidol, all the tested drugs blocked trophozoite differentiation into cysts in encystation assays. Given the limited availability of effective drugs to treat amoebal infections, the clinically available drugs tested in this study represent potential agents for managing keratitis and granulomatous amoebic encephalitis caused by Acanthamoeba spp. and possibly against other meningoencephalitis-causing amoebae, such as Balamuthia mandrillaris and Naegleria fowleri.