Flunarizine. A reappraisal of its pharmacological properties and therapeutic use in neurological disorders

Ratanasampil is more effective than flunarizine in relieving migraine

Aims: Migraine is a common neurological disorder with high incidence in population. This study aimed to investigate the therapeutic efficacy of Tibetan medicine Ratanasampil (RNSP) and to identify the serum biomarkers for diagnosis and response assessment.Materials and methods: We prospectively recruited 108 migraine patients living at high altitude (2,260 m), including 40 patients for RNSP group, 40 patients for flunarizine (FLZ) group, and 28 patients for placebo group. Serum levels of 5-hydroxytryptamine (5-HT), brain-derived neurotrophic factor (BDNF), calcitonin gene related peptide (CGRP), nerve growth factor (NGF) and β-endorphin (β-EP) before and after therapy were measured.Results: In comparison with placebo, both FLZ and RNSP significantly reduced the migraine days, HIT-6 score and verbal rating scale, headache intensity, duration, accompanying symptoms and headache score in four and eight weeks treatment. RNSP showed no significant difference to FLZ in the above parameters after four weeks treatment, but showed significantly better relief after eight weeks treatment. The overall effective rate of RNSP (92.5%) was also significantly higher than FLZ (74.4%, p < 0.05), mainly due to significantly higher ratio of patients with full recovery. The serum levels of biomarkers, including 5-HT, BDNF, NGF and β-EP, significantly elevated after eight weeks of treatment with RNSP, whereas the level of CGRP significantly decreased. The serum level of 5-HT exhibited significantly bigger percentage changes than other markers.Conclusion: In conclusion, RNSP was more effective than FLZ in relieving migraine after eight weeks continuous treatment. Serum 5-HT, BDNF, CGRP, NGF and β-EP were effective markers reflecting the response to RNSP and FLZ therapy.

The Pharmacological Treatment of Pediatric Vertigo

Vertigo in children is a challenging topic. The lack of dedicated trials, guidelines and papers causes inhomogeneity in the treatment of vertigo in children. Meniere’s disease, migraine equivalents, vestibular neuritis, paroxysmal positional benign vertigo (BPPV), persistent postural-perceptual dizziness (PPPD) and motion sickness may affect children with various degrees of incidence and clinical severity compared to adults. Several drugs are proposed for the management of these conditions, even if their use is subordinated to the child’s age. In this review, we summarize the existing evidence related to the use of drugs for this clinical condition in children as a start point for new trials, stating the urgent need for international guidelines.

Styryl Group, a Friend or Foe in Medicinal Chemistry

The styryl (Ph-CH=CH-R) group is widely represented in medicinally important compounds, including drugs, clinical candidates, and molecular probes as it positively impacts the lipophilicity, oral absorption, and biological activity. The analysis of matched molecular pairs (styryl vs. phenethyl, phenyl, methyl, H) for the biological activity indicates the superiority aspect of styryl compounds. However, the Michael acceptor site in the styryl group makes it amenable to the nucleophilic attack by biological nucleophiles and transformation to the toxic metabolites. One of the downsides of styryl compounds is isomerization that impacts the molecular conformation and directly affects biological activity. The impact of cis-trans isomerism and isosteric replacements on biological activity is exemplified. We also discuss the styryl group-bearing drugs, clinical candidates, and fluorescent probes. Overall, the present review reveals the utility of the styryl group in medicinal chemistry and drug discovery.

Pharmacokinetics of Flunarizine Hydrochloride After Single Oral Doses in Healthy Subjects: Bioequivalence Study and Food Effects

We designed a study to compare the newly developed 5-mg flunarizine hydrochloride capsules (test) to that of its marketed counterpart (5-mg; reference) among healthy adult Chinese volunteers. We performed an open-label, single-center study that consisted of 2 randomized, crossover trials, including a fasting trial and a fed trial. In each part of the study, the subjects were randomly assigned to either receive the test or reference products (5-mg flunarizine) in a 1:1 ratio. Subjects then received the alternative products, following a 14-day washout period. Concentrations of plasma flunarizine were analyzed using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters (noncompartmental model) were evaluated using the WinNonlin software. The analysis of variance and Food and Drug Administration bioequivalence statistical criterion of 90% confidence interval for 80% to 125% range (set at P ≤ .05) of geometric means ratios of test: reference product for peak plasma concentration, area under the plasma concentration-time curve (AUC) from time 0 to time t, and AUC from time 0 to infinity were determined. Tolerability was evaluated during the entire study period. Overall, 23 volunteers completed the fasting study, while 40 volunteers completed the fed study. The test formulation was found to be bioequivalent to the marketed formulation, as the 90% confidence interval for the ratio of geometric means of peak plasma concentration (fasting: 87.61%-101.67%; fed: 87.38%-104.06%), AUC from time 0 to time t (fasting: 89.44%-99.92%; fed: 92.65%-98.28%), and AUC from time 0 to infinity (fasting: 95.02%-104.33%; fed: 90.41%-96.96%) were within equivalence limits (80-125%) under both the fasting and fed conditions. When flunarizine was given alongside high-fat meals, time to maximum concentration was delayed ≈3.5 hours compared to fasting conditions. Meantime, high-fat meals increased its exposure by nearly 50%. Furthermore, there were no serious adverse events found among the subjects. This study confirmed that test and reference flunarizine hydrochloride capsules were bioequivalent under fasting and postprandial conditions.

Inhibition of gap junctional intercellular communication by an anti-migraine agent, flunarizine

Gap junctions (GJs), which consist of proteins called connexins, are intercellular channels that allow the passage of ions, second messengers, and small molecules. GJs and connexins are considered as emerging therapeutic targets for various diseases. Previously, we screened numerous compounds using our recently developed iodide yellow fluorescent protein gap junctional intercellular communication (I-YFP GJIC) assay and found that flunarizine (FNZ), used for migraine prophylaxis and as an add-on therapy for epilepsy, inhibits GJIC in LN215 human glioma cells. In this study, we confirmed that FNZ inhibits GJIC using the I-YFP GJIC assay. We demonstrated that FNZ inhibits GJ activities via a mechanism that is independent of calcium channels and dopaminergic D2, histaminergic H1, or 5-HT receptors. In addition, we showed that FNZ significantly increases connexin 43 (Cx43) phosphorylation on the cell surface, but does not alter the total amount of Cx43. The beneficial effects of FNZ on migraines and epilepsy might be related to GJ inhibition.

Simulation of phase I metabolism reactions of selected calcium channel blockers by human liver microsomes and photochemical methods with the use of Q-TOF LC/MS

The in vitro phase I metabolism of perhexiline and flunarizine, two calcium channel blockers was investigated during this study with the use of human liver microsomes (HLM) method compared with TiO₂, WO₃ and ZnO catalyzed photochemical reaction. In order to determine the structures of metabolites an quadrupole time-of-flight mass spectrometry combined with liquid chromatography (Q-TOF LC/MS) system was used. The obtained high resolution mass spectra enabled to identify thirteen products of metabolism of selected drugs including three not yet described metabolites of perhexiline and two new metabolites of flunarizine. The vast majority of metabolites were confirmed also with the participation of photocatalytic approach of the drug metabolism simulation. The comparison of all metabolic profiles made with the use of computational methods drew attention particularly to TiO₂ and WO₃ catalyzed photochemical reaction as similar to HLM incubation. Additionally, in silico toxicity assessment of the detected transformation products of the analyzed substances was also evaluated.

A high-throughput LC-MS/MS method for determination of flunarizine in human plasma: Pharmacokinetic study with different doses

A high-throughput and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the determination of flunarizine in human plasma. Liquid-liquid extraction under acidic conditions was used to extract flunarizine and flunarizine-d8 from 100 μL human plasma. The mean extraction recovery obtained for flunarizine was 98.85% without compromising the sensitivity of the method. The chromatographic separation was performed on Hypersil Gold C₁₈ (50 × 2.1 mm, 3 μm) column using methanol-10 mm ammonium formate, pH 3.0 (90:10, v/v) as the mobile phase. A tandem mass spectrometer (API-5500) equipped with an electrospray ionization source in the positive ion mode was used for detection of flunarizine. Multiple reaction monitoring was selected for quantitation using the transitions, m/z 405.2 → 203.2 for flunarizine and m/z 413.1 → 203.2 for flunarizine-d8. The validated concentration range was established from 0.10 to 100 ng/mL. The accuracy (96.1-103.1%), intra-batch and inter-batch precision (CV ≤ 5.2%) were satisfactory and the drug was stable in human plasma under all tested conditions. The method was used to evaluate the pharmacokinetics of 5 and 10 mg flunarizine tablet formulation in 24 healthy subjects. The pharmacokinetic parameters C_max and AUC were dose-proportional.

Flunarizine for Headache Prophylaxis in Children With Sturge-Weber Syndrome

BACKGROUND

Children with Sturge-Weber syndrome can experience severe headache with or without transient hemiparesis. Flunarizine, a calcium antagonist, has been used for migraine. The experience with flunarizine for headache in a cohort of children at a national center for Sturge-Weber syndrome is reviewed, reporting its efficacy and adverse effect in this population.

METHODS

We collected data from health care professionals' documentation on headache (severity, frequency, duration) before and on flunarizine in 20 children with Sturge-Weber syndrome. Adverse effects reported during flunarizine treatment were collated. The Wilcoxon signed rank test was used to determine the significance of pre- versus post-treatment effect.

RESULTS

Flunarizine was used for headache alone (13) or mixed migrainous episodes and vascular events (7). The median duration of treatment was 145 days (range 43 to 1864 days). Flunarizine reduced headache severity (z = -3.354, P = 0.001), monthly frequency (z = -2.585, P = 0.01), and duration (z = -2.549, P = 0.01). Flunarizine was discontinued owing to intolerable adverse effects in a minority (2). Sedation and weight gain were the most common side effects. There were no reports of behavior change or extrapyramidal features.

CONCLUSIONS

The most effective management for headaches in patients with Sturge-Weber syndrome has not been established. This retrospective observational study found benefit of flunarizine prophylaxis on headache severity, frequency, and duration in children with Sturge-Weber syndrome without severe side effects. Flunarizine is not licensed for use in the United Kingdom, but these data support its off-license specialist use for headache prophylaxis in Sturge-Weber syndrome.

Comparison of the Efficacy and Safety of Flunarizine to Propranolol in the Prophylaxis of Migraine

This study was designed to compare flunarizine, a cerebro-specific calcium channel antagonist, and propranolol in the prophylaxis of migraine with or without aura. Following a 1 month single-blind placebo baseline period, 94 patients were equitably randomised under double-blind conditions to take flunarizine 10 mg daily or propranolol 80 mg twice daily for 4 months. Both treatments led to a significant reduction in the frequency of migraines and use of rescue analgesics with a significantly greater decrease in number of attacks for flunarizine after 1 and 4 months. Neither treatment affected the severity nor duration of migraines. Overall, 67% of flunarizine patients and 51 % of propranolol patients responded positively. Propranolol significantly reduced blood pressure and heart rate; flunarizine had no effect on cardiovascular function. Weight gain was noted with both treatments. Flunarizine is at least as effective as propranolol in the prophylactic treatment of migraine and may have a better safety profile.

Management of vestibular migraine

Vestibular migraine is considered to be the second most common cause of vertigo and the most common cause of spontaneous episodic vertigo. The duration of attacks varies from seconds to days, usually lasting minutes to hours, and they mostly occur independently of headaches. Long-lasting individual attacks are treated with generic antivertiginous and antiemetic drugs. Specific antimigraine drugs are unlikely to be very effective for rescue. The mainstay of the management of vestibular migraine is prophylactic medication. To date, there are no controlled trials available; the body of knowledge builds on case series and retrospective or observational studies. Most drugs are also used for the prevention of migraine headaches. The choice of medication should be guided by its side effect profile and the comorbidities of patients. Betablockers such as propanolol or metoprolol are preferred in patients with hypertension but in the absence of asthma. Anticonvulsants include topiramate when patients are obese, valproic acid and lamotrigine. Lamotrigine is preferred if vertigo is more frequent than headaches. Calcium antagonists include verapamil and flunarizine. If patients have anxiety, tricyclic antidepressants such as amitryptiline or nortryptiline or SSRIs and benzodiazepines such as clonazepam are recommended. Acetazolamide is effective in rare genetic disorders related to migraine-like episodic ataxia; however, its place in vestibular migraine is still to be established. Nonpharmacological measures such as diet, sleep, hygiene and avoidance of triggers are recommended as they are for migraine. Vestibular rehabilitation might be useful when there are complications such as loss of confidence in balance or visual dependence.

Effect of flunarizine, a calcium channel blocker, on intraocular pressure and aqueous humor dynamics in monkeys

PURPOSE

To evaluate the effects of flunarizine, a nonselective calcium channel blocker, on intraocular pressure (IOP) in monkeys with laser-induced unilateral glaucoma and on aqueous humor dynamics in normal monkeys.

METHODS

The IOP was measured before and hourly for 6 hours after single-dose administration of 0.5%, 1%, or 2% flunarizine to the glaucomatous eye of 8 monkeys with unilateral laser-induced glaucoma. In a separate multiple-dose study, 0.5% flunarizine was applied twice daily for 5 consecutive days to the glaucomatous eye of the same 8 monkeys. IOP was measured at untreated baseline, after treatment with vehicle only, and on treatment days 1, 3, and 5. Tonographic outflow facility and fluorophotometric flow rates of aqueous humor were measured in 7 normal monkeys before and after the fifth dose of twice-daily treatment with 0.5% flunarizine.

RESULTS

Unilateral application of 50 microL of 0.5%, 1%, or 2% flunarizine reduced IOP bilaterally. In the treated glaucomatous eyes, flunarizine reduced the IOP for 2, 3, or 5 hours, with a maximum reduction of 2.5+/-0.5 (mean+/-SEM) mm Hg (9%), 3.0+/-0.4 mm Hg (10%), and 5.0+/-0.8 mm Hg (18%) following the 0.5%, 1%, and 2% concentrations, respectively (P<0.01). The maximum reductions in IOP in the contralateral untreated eyes were 1.3+/-0.5 mm Hg, 1.5+/-0.3 mm Hg, and 2.9+/-0.7 mm Hg following the 0.5%, 1%, and 2% concentrations, respectively (P<0.05). Both the magnitude and duration of the ocular hypotensive effect of 0.5% flunarizine were enhanced with twice-daily administration for 5 days. Outflow facility in normal monkey eyes was increased (P<0.05) by 39% in the treated eyes compared with vehicle-treated contralateral eyes and by 41% compared with baseline values, and aqueous humor flow rates were unchanged (P>0.30).

CONCLUSIONS

Flunarizine reduces IOP in a dose-dependent manner when administered to glaucomatous monkey eyes, but also has an ocular hypotensive effect on the contralateral untreated eyes. An increase in tonographic outflow facility seems to account for the IOP reduction in normal monkey eyes.

Pharmacogenomics and migraine: possible implications

Pharmacogenomics is the science about how inherited factors influence the effects of drugs. Drug response is always a result of mutually interacting genes with important modifications from environmental and constitutional factors. Based on the genetic variability of pharmacokinetic and in some cases pharmacodynamic variability we mention possible implications for the acute and preventive treatment of migraine. Pharmacogenomics will most likely in the future be one part of our therapeutic armamentarium and will provide a stronger scientific basis for optimizing drug therapy on the basis of each patient’s genetic constitution.

In vitro plasma protein binding determination of flunarizine using equilibrium dialysis and liquid chromatography-tandem mass spectrometry

A highly sensitive method was developed and validated for determining the free fraction of flunarizine in human plasma. Equilibrium dialysis was used for the separation of free (unbound) drug and liquid chromatography/tandem mass spectrometry (LC-MS/MS) was used for quantitation. Post-dialysis plasma or buffer samples of 0.2 mL were extracted using a liquid-liquid extraction procedure and analyzed using a high performance liquid chromatography electrospray tandem mass spectrometer system. The compounds were eluted isocratically on a Supelco Supelcosil ABZ+Plus column, ionized using a positive ion atmospheric pressure electrospray ionization source, and analyzed using multiple reaction monitoring. The ion transitions monitored were m/z 405-->203 for flunarizine and m/z 409-->207 for flunarizine-d4 (internal standard, IS). The chromatographic run time was 3.5 min per injection, with retention times of 2.1 min for both flunarizine and IS. The calibration curve for flunarizine was linear over the concentration range of 0.25-2000 ng/mL (r(2)>0.9989) in the combined matrix of human plasma and isotonic sodium phosphate buffer (1:1, v/v) with the lower limit of quantitation of 0.25 ng/mL. The inter-assay coefficient of variability (CV) for the quality control samples was less than 13.5%, and the inter-assay percent nominal was greater than 98.2%. In vitro protein binding of flunarizine was determined at concentrations of 5, 10 and 100 microg/mL using the validated method. Flunarizine was extensively bound to plasma protein with a 0.083+/-0.005% overall percent free drug in plasma and a CV value less than 7.8%. This validated method will be used for the ex vivo assessment of flunarizine protein binding in human plasma from a drug-drug interaction clinical study.

Atypical antipsychotic profile of flunarizine in animal models

RATIONALE

Flunarizine is known as a calcium channel blocker commonly used in many countries to treat migraine and vertigo. Parkinsonism has been described as one of its side-effects in the elderly, which is in agreement with its recently characterized moderate D2 receptor antagonism.

OBJECTIVES

To perform a pre-clinical evaluation of flunarizine as a potential antipsychotic.

METHODS

We evaluated the action of orally administered flunarizine in mice against hyperlocomotion induced by amphetamine and dizocilpine (MK-801) as pharmacological models of schizophrenia, induction of catalepsy as a measure for extrapyramidal symptoms and impairment induced by dizocilpine on the delayed alternation task for working memory.

RESULTS

Flunarizine robustly inhibited hyperlocomotion induced by both amphetamine and dizocilpine at doses that do not reduce spontaneous locomotion (3-30 mg/kg). Mild catalepsy was observed at 30 mg/kg, being more pronounced at 50 mg/kg and 100 mg/kg. Flunarizine (30 mg/kg) improved dizocilpine-induced impairment on the delayed alternation test.

CONCLUSIONS

These results suggest a profile comparable to atypical antipsychotics. The low cost, good tolerability and long half-life (over 2 weeks) of flunarizine are possible advantages for its use as an atypical antipsychotic. These results warrant clinical trials with flunarizine for the treatment of schizophrenia.

Anticonvulsant profile of flunarizine and relation to Na(+) channel blocking effects

The present study will summarize our findings concerning the anticonvulsant properties of the Ca2+ channel blocker flunarizine in a variety of experimental models of epilepsy. Flunarizine exhibits anticonvulsant effects against tonic seizures induced by electroshock or various chemoconvulsants in mice, however, did not protect against pentylenetetrazol-induced clonic seizures. In the MES test, the efficacy of clinically established antiepileptics was increased by co-medication. In the rotarod test, a minimal "neurotoxic" dose (TD50) of 18.0 mg/kg intraperitoneally was determined. In models of complex partial seizures like the hippocampal stimulation and the amygdala kindling in rats, flunarizine showed only a moderate activity. Thus, it can be suggested that the anticonvulsant potency of flunarizine in various screening tests is lower than that of standard antiepileptics such as carbamazepine and phenytoin. Concerning the possible mode of action, whole-cell patch-clamp experiments with cultured neonatal rat cardiomyocytes showed that flunarizine depressed the fast inward Na+ current in a concentration- and frequency-dependent manner well comparable with the action of phenytoin. It is concluded that the use-dependent inhibition of voltage-dependent Na+ channels may essentially contribute to the anticonvulsant activity of flunarizine in models for generalized tonic-clonic seizures. The clinical efficacy as add-on therapy is critically discussed in view of the present data.

Pharmacokinetic profile of topical flunarizine in rabbit eye and plasma

The purpose of this study was to determine the aqueous humor, cornea, iris-ciliary body, retina and plasma levels and pharmacokinetics of a new topical formulation containing 0.05% flunarizine upon single drop application. Albino rabbits were used and tissue samples were collected at 15, 30, 60, 120 and 240 min after instillation. Drug concentrations in ocular tissues and plasma were measured by gas chromatography assay. After single dose application peak levels of drug were achieved at 15 min in cornea and at 30 min in aqueous humor, iris-ciliary body and retina. Unilateral topical flunarizine caused a significant reduction of intraocular pressure in rabbits. The pharmacokinetic profile showed a good ocular bioavailability of the drug providing that the new topical formulation containing 0.05% flunarizine reach the target tissues at effective concentrations and therefore may be use in the treatment of glaucoma.

Inherited muscle and brain channelopathies

In the past 5 years, advances in the complementary fields of neurogenetics and cellular electrophysiology have resulted in an explosion of knowledge about a group of disorders now known as the neurological channelopathies. These advances have resulted in more accurate DNA-based diagnosis and have increased our understanding of cellular pathophysiology. This is leading to more tailored therapies for patients with these disorders.

Determination of flunarizine in rat brain by liquid chromatography-electrospray mass spectrometry

A rapid liquid chromatography-electrospray mass spectrometry (LC-ES-MS) assay for the determination of flunarizine (FZ) in rat brain has been developed. A C18 column and an isocratic elution were employed for the separation. Using post-column split, 64% of the eluent was introduced into the ES-MS system for detection. The [M+H]+ (m/z 406) and a fragmented ion (m/z 203) were detected using selected ion monitoring. The linear range of this assay was good, ranging from 0.05 to 5 microM (r2=0.99). The intra- and inter-day precisions showed relative standard deviations ranging from 1.4% to 2.0% and 1.3% to 2.9%, respectively. The application of this newly developed method was demonstrated by examining the pharmacokinetics of FZ in rat brain.

Drug-induced parkinsonism: cinnarizine and flunarizine are potent uncouplers of the vacuolar H+-ATPase in catecholamine storage vesicles

Cinnarizine (1-diphenylmethyl-4-(3-phenyl-2-propenyl)piperazine) and its di-fluorinated derivative flunarizine inhibit the MgATP-dependent generation of a transmembrane proton electrochemical gradient in chromaffin granule ghosts. The concentrations giving 50% inhibition (IC50) of the MgATP-dependent generation of the pH-gradient were 5.9+/-0.6 microM (n = 6) and 3.0+/-0.3 microM (n = 5) for cinnarizine and flunarizine, respectively. The IC50 values for inhibiting the generation of the membrane potential were even lower, i.e. 0.19+/-0.06 microM (n = 6) and 0.15+/-0.01 microM (n = 4) for cinnarizine and flunarizine, respectively. Cinnarizine (10 microM) also inhibited the energy-dependent vesicular uptake of [14C]-dopamine (50 microM) by 76%, i.e. from 2.1+/-0.9 to 0.5+/-0.6 nmol/mg protein/min (n = 5, P < 0.002). Cinnarizine (10 microM) increased the MgATPase activity of the granule ghosts by 47+/-26% (n = 4) compatible with an uncoupling of the vacuolar H+-ATPase activity. The IC50-values observed for the two compounds are in the same range as their reported therapeutic plasma concentrations in vivo, suggesting that cinnarizine and flunarizine may well inhibit proton pumping and catecholamine uptake in storage vesicles also in vivo. This mechanism of action may contribute to the drug-induced parkinsonism seen as a side-effect of the two drugs.

Neuroprotective effects of lamotrigine enhanced by flunarizine in gerbil global ischemia

We examined whether the anti-ischemic effect of lamotrigine (LTG), which inhibits the presynapic sodium channel, could be enhanced by the calcium channel blocker-flunarizine (FNR) in cerebral ischemia. Global ischemia was induced in Mongolian gerbils for 5 min under the monitoring of scalp temperature. LTG and FNR were administered intraperitoneally 1 h before ischemia. After 7 days, animals were killed and viable neurons in CA1 area were counted. LTG treated group showed significant protective effects compared to control group (P < 0.01). These effects were more prominent in group treated with LTG and FNR (P = 0.01). Combination of two drugs did not increase the mortality rate compared to single-treated group. These results show that a synergistic reduction of neuronal death can be achieved by combination of LTG and FNR without serious adverse reaction.

Effects of dotarizine and flunarizine on chromaffin cell viability and cytosolic Ca2+

Dotarizine (a novel piperazine derivative with antimigraine properties) and flunarizine (a Ca2+ channel antagonist) were compared concerning: first, their ability to cause chromaffin cell damage in vitro; second, the possible correlation of their octanol/water partition coefficients and those of another 28 compounds (i.e., Ca2+ channel antagonists, blockers of histamine H1 receptors, antimycotics, beta-adrenoceptor antagonists, neuroleptics), with their ability to cause cell damage; third, their capacity to protect the cells against the damaging effects of veratridine; and fourth, their capabilities to enhance the basal cytosolic Ca2+ concentration in fura-2-loaded single chromaffin cells, or to modify the pattern of [Ca2+]i oscillations elicited by veratridine. After 24-h exposure to 1-30 microM dotarizine, the viability of bovine adrenal chromaffin cells (measured under phase contrast or as lactate dehydrogenase, released into the medium) was similar to that of control, untreated cells; at 100 microM, 80% lactate dehydrogenase release was produced. At 1-3 microM flunarizine caused no cell damage; however 10 microM caused 20% lactate dehydrogenase release and 30 and 100 microM over 90% lactate dehydrogenase release. The time course of cell damage was considerably faster for flunarizine, in comparison to dotarizine. Out of 30 molecules tested (at 10 microM), having different octanol/water partition coefficients (log P), dotarizine was among the molecules causing no cell damage; flunarizine caused 20% cell loss, lidoflazine and verapamil over 50% cell loss, and penfluridol, draflazine, astemizole or nifedipine over 80% cell loss. No correlation was found between log P and cytotoxicity. Both dotarizine (10-30 microM) and flunarizine (3-10 microM) provided protection against veratridine-induced cell death; however, at 30 microM dotarizine afforded a pronounced protection while flunarizine enhanced the cytotoxic effects of veratridine. Dotarizine (30 microM) (but not flunarizine) caused a prompt transient elevation of the basal [Ca2+]i. Both compounds abolished the K+-induced increases of [Ca2+]i as well as the oscillations of [Ca2+]i induced by veratridine. The blocking effects of dotarizine were readily reversed after washout, while those of flunarizine were long-lasting. These differences might be relevant to the clinical use of dotarizine as an antimigraine drug.

Low dose flunarizine protects the fetal brain from ischemic injury in sheep

Flunarizine, a calcium channel blocker, reduced cerebral damage caused by hypoxic-ischemic insults in neonatal rats and in fetal sheep near term. However, the high dose regimen used in these studies produced cardiovascular side effects that might have counteracted the neuroprotective properties of flunarizine. Therefore, the neuroprotective effect was tested in a low dose protocol (1 mg/kg estimated body weight). Twelve fetal sheep near term were instrumented chronically. Six fetuses were pretreated with 1 mg of flunarizine per kg of estimated body weight 1 h before ischemia, whereas the remainder (n=6) received solvent. Cerebral ischemia was induced by occluding both carotid arteries for 30 min. To exclude the possibility that the neuroprotective effects of flunarizine were caused by cerebrovascular alterations we measured cerebral blood flow by injecting radiolabeled microspheres before (-1 h), during (3 min and 27 min) and after (40 min, 3 h, and 72 h) cerebral ischemia. At the end of the experiment (72 h) the ewe was given a lethal dose of sodium pentobarbitone and saturated potassium chloride i.v., and the fetal brain was perfused with formalin. Neuronal cell damage was assessed in various brain structures by light microscopy after cresyl violet/fuchsin staining using a scoring system: 1, 0-5% damage; 2, 5-50% damage; 3, 50-95% damage; 4, 95-99% damage; and 5, 100% damage. In 10 other fetal sheep effects of low dose flunarizine on circulatory centralization caused by acute asphyxia could be excluded. In the treated group neuronal cell damage was reduced significantly in many cerebral areas to varying degrees (range for control group, 1.03-2.14 versus range for treated group, 1.00-1.13; p < 0.05 to p < 0.001, respectively). There were only minor differences in blood flow to the various brain structures between groups. We conclude that pretreatment with low dose flunarizine protects the brain of fetal sheep near term from ischemic injury. This neuroprotective effect is not mediated by changes in cerebral blood flow. We further conclude that low dose flunarizine may be clinically useful as a treatment providing fetal neuroprotection, particularly because the fetal cardiovascular side effects are minimal.

Anticonvulsant effects of nimodipine and two novel dihydropyridines (PCA 50922 and PCA 50941) against seizures elicited by pentylenetetrazole and electroconvulsive shock in mice

In animal models of epilepsy, calcium entry blockers have shown anticonvulsant properties. We studied the antiepileptic effects of nimodipine and two novel dihydropyridines, a calcium antagonist (PCA 50922) and a calcium agonist (PCA 50941), on pentylenetetrazole seizure and maximal electroshock seizure (MES) in mice. Anticonvulsant profile of nimodipine and PCA 50922 was similar to that of clonazepam, but markedly different from that of phenytoin. None of the doses of the PCA 50941 showed anticonvulsant effect.

The effect of Dotarizine (Ca2+ channel blocker) on cerebral vessel reactivity in animals subjected to hyperventilation and anoxia

Dotarizine--a novel piperazine derivative--belongs to wide spectrum Ca+ channel antagonists. It was reported to have strong vasodilatory and antiserotoninergic activities. Unlike other Ca+ channel blockers Dotarizine was found to have lower oral toxicity. In the presented study the influence of the oral administration of the novel compound on the blood flow velocity changes in different cerebral arteries--in basilar artery (BA) and middle cerebral artery (MCA)--was investigated under hyperventilation and hypoxic conditions of rabbits. In the first experimental group 25 mg/kg of Dotarizine dissolved in 0.25% agar was administered orally three times at the 10 hours' intervals. The sham group of animals was fed with agar of the same concentration. The results revealed that oral administration of Dotarizine diminished the vasoconstrictive effect of hyperventilation and this was more pronounced in MCA than in BA. During anoxic conditions stronger vasodilatory effects were observed in both groups of vessels and the low value of pulsatility index (PI) reflected pronounced decrease of the peripheral resistance, in comparison to the control group. Thus, the oral administration of Dotarizine decreases the peripheral resistance of cerebral vessels and therefore seems to have influence on the minute arteries of cerebrovascular system of the brain.

Neuroprotective therapy for argon-laser induced retinal injury

Laser photocoagulation treatment of the central retina is often complicated by an immediate side effect of visual impairment, caused by the unavoidable laser-induced destruction of the normal tissue lying adjacent to the lesion and not affected directly by the laser beam. Furthermore, accidental laser injuries are at present untreatable. A neuroprotective therapy for salvaging the normal tissue might enhance the benefit obtained from treatment and allow safe perifoveal photocoagulation. We have developed a rat model for studying the efficacy of putative neuroprotective compounds in ameliorating laser-induced retinal damage. Four compounds were evaluated: the corticosteroid methylprednisolone, the glutamate-receptor blocker MK-801, the anti-oxidant enzyme superoxide dismutase, and the calcium-overload antagonist flunarizine. The study was carried out in two steps: in the first, the histopathological development of retinal laser injuries was studied. Argon laser lesions were inflicted in the retinas of 18 pigmented rats. The animals were killed after 3, 20 or 60 days and their retinal lesions were evaluated under the light microscope. The laser injury mainly involved the outer layers of the retina, where it destroyed significant numbers of photoreceptor cells. Over time, evidence of two major histopathological processes was observed: traction of adjacent normal retinal cells into the central area of the lesion forming an internal retinal bulging, and a retinal pigmented epithelial proliferative reaction associated with subretinal neovascularization and invasion of the retinal lesion site by phagocytes. The neuroprotective effects of each of the four compounds were verified in a second step of the study. For each drug tested, 12 rats were irradiated with argon laser inflictions: six of them received the tested agent while the other six were treated with the corresponding vehicle. Twenty days after laser exposure, the rats were killed and their lesions were subjected to image-analysis morphometry. The extent of retinal destruction was assessed by measuring the lesion diameter and the amount of photoreceptor cell loss in the outer nuclear layer. Methylprednisolone and MK-801 were shown to ameliorate laser-induced retinal damage, whereas both superoxide dismutase and flunarizine were ineffective. Furthermore, MK-801 diminished the proliferative reaction of the retinal pigment epithelial cells. On the basis of our results we suggest that the pigmented rat model is suitable for studying and screening various compounds for their neuroprotective efficacy in treating retinal laser injury. We further suggest that glutamate might play a key role in mediating retinal injury induced by laser irradiation.

Dose-dependent effect of betahistine on the vestibulo-ocular reflex: a double-blind, placebo controlled study in patients with paroxysmal vertigo

The effect of betahistine on the vestibulo-ocular reflex (VOR) was assessed in 12 patients suffering from paroxysmal vertigo. Only patients who responded to betahistine treatment were admitted to the study in order to increase the probability of quantifying the effect of the drug on vestibular function. Patients received placebo or 16, 32 or 64 mg betahistine orally under double-blind conditions. Vestibular function was tested a few minutes before intake, and 1, 2, 3, 4, 6 and 8 h after intake, by torsion swing stimulus in the dark, visuo-vestibular interaction upon simultaneous visual and vestibular stimulation and high frequency passive head shaking. Betahistine significantly affected the velocity gain of low and high frequency VOR. The reduction in gain was maximal about 4 h after administration of the 16 mg dose in the torsion swing experiment and the 32 mg dose in the head shaking experiment. Above these doses, the effect on velocity gain was less marked. Betahistine had no effect on visuo-vestibular interaction or nystagmus duration during low frequency torsion. These results suggest that betahistine has a complex action on H3 receptors and that the site of action may be in the vestibular nuclei.

Serotonergic effects of dotarizine in coronary artery and in oocytes expressing 5-HT2 receptors

In strips of pig coronary arteries incubated in oxygenated Krebs-bicarbonate solution at 37 degrees C, dotarizine blocked the phasic contractions evoked by 5-HT (0.5 microM) or K+ depolarization (35 mM K+) with an IC50 of 0.22 and 3.7 microM, respectively. Flunarizine inhibited both types of contractions with IC50 values of 1.7 microM for 5-HT and 2.4 microM for K+ responses. In Xenopus oocytes injected with in vitro transcribed RNA encoding for 5-HT2A or 5-HT2C receptors, 5-HT (100 nM for 20 s) applied every 10 min caused, in both cases, a reproducible inward current through Ca2(+)-activated Cl- channels (ICl). Dotarizine inhibited the 5-HT2A response in a concentration-dependent manner, with an IC50 of 2.2 nM. In contrast, the 5-HT2C response was unaffected by 1 microM dotarizine and blocked around 62% by 10 microM of this drug. The ICl activated either by intracellular injection of inositol 1,4,5-trisphosphate (IP3) in oocytes or by direct photorelease of Ca2+ in DM-nitrophen-injected oocytes was unaffected by 10 microM dotarizine. It is concluded that dotarizine blocks 5-HT2A receptors with a high affinity; the compound is devoid of intracellular effects on any further steps of the transduction pathway (i.e., IP3 receptor). Contrary to flunarizine that blocks equally well the serotonergic and the K+ vascular responses, dotarizine exhibits 17-fold higher affinity for vascular 5-HT receptors. These findings might be relevant to an understanding of the mechanism involved in the use of dotarizine and flunarizine as prophylactic agents in migraine.

'Wide-spectrum Ca2+ channel antagonists': lipophilicity, inhibition, and recovery of secretion in chromaffin cells

Repetitive application of short depolarizing K+ pulses (70 mM K+, 2 mM Ca2+ Krebs-HEPES solution, for 10 s every 5 min) produced reproducible catecholamine secretory responses from superfused bovine chromaffin cells. At 10 microM for 15 min, the piperazine derivatives dotarizine, flunarizine and lidoflazine inhibited secretion by around 90%; cinnarizine halved the secretory response. Recovery of secretion after 30-min washout with Krebs-HEPES solution amounted to 75% in the case of dotarizine, 8% for flunarizine, 46% for lidoflazine and 21% for cinnarizine. The benzothiazol derivatives (10 microM) (+)-S-lubeluzole and R91154 (the (-)-R-enantiomer of lubeluzole) blocked the response by 75%; sabeluzole inhibited secretion by only 34% and R56865 (N-[1-(4-(4-fluorophenoxy)butyl]-4-piperidinyl-N-methyl-2-benzo-thiaz olamine) by 61%. Recoveries were around 70% in the case of these four benzothiazol derivatives. The diphenylbutyl-piperazine derivatives fluspirilene and penfluridol inhibited secretion by over 80%; no recovery was produced after 30-min washout. The inhibition of secretion was time dependent, as the recovery of the response was. Blockade of secretion by dotarizine and flunarizine occurred even in the absence of intermittent K+ stimulations of the cells. No obvious correlation was seen between the octanol/water partition coefficients of the ten compounds tested (that ranged between 6 and 4.61), the rate and extent of blockade of secretion, and the recovery of the secretory response upon washout. Rather than non-specific actions on ion channels (and secretion) due to their high lipophilicity, we believe that blockade of various Ca2+ channels relates to their binding properties to specific channel micro and macrodomains, as the case might be for 'narrow' (omega-conotoxin GVIA) and 'wide-spectrum' (omega-conotoxin MVIIC) peptide toxins.

Effects of the calcium channel blockers Dotarizine and Flunarizine on cerebrovascular reactivity

Dotarizine and Flunarizine are piperazine derivatives considered to be effective compounds for the treatment of various cerebrovascular disorders. In the present study the influence of these two drugs on changes in cerebral vessel diameter and blood flow velocity were measured and compared utilising transcranial Doppler sonography during hyperventilation in anaesthetized cats. Drugs were administered in 15 min intravenous infusions at a dose of 0.05 mg/kg/min. This investigation revealed that the 15 min intravenous administration of both compounds abolished the cerebral vasoconstrictor effects of hyperventilation and due to vasodilator effects they increased blood flow velocity to initial values. No statistically significant differences were found between the vasodilator effects of Dotarizine and Flunarizine. Results obtained suggest that Dotarizine, a novel piperazine derivative, has similar vasodilator and Ca2+ channel blocking effects on cerebrovascular reactivity compared to the widely clinically applied Flunarizine.

A review of the treatment of primary headaches. Part I: Migraine

Finding the best treatment for a patient's migraine is often a problem in clinical practice since the condition is very common, often debilitating and may prove refractory to therapy. Over recent years, more effective migraine treatments have been found and validated, and the traditional remedies have undergone controlled testing. This article reviews the various therapies available for both the acute treatment and prevention of migraine. Treatments often effective against migraine attacks are: aspirin, analgesics, non steroid anti-inflammatory drugs (NSAIDs), ergot derivatives and sumatriptan. Five main classes of prophylactic drug are currently used: beta-blockers, calcium antagonists, serotonin modulators, NSAIDs and ergot compounds. Biofeedback, one of the most efficacious non-pharmacological preventive treatments of migraine, is also discussed. The variables influencing the choice of acute and preventive treatments, including contraindications and drug availability, are also described in order to provide a practical and up-to-date guide to migraine therapy.

Possible pharmacokinetic and pharmacodynamic factors affecting parkinsonism inducement by cinnarizine and flunarizine

Potentialities of cinnarizine [1-(diphenylmethyl)-4-(3-phenyl-2-propenyl)piperazine, CZ] and its fluorine derivative flunarizine [1-[bis(4-fluorophenyl)-methyl]-4-(3-phenyl-2-propenyl)piperazine, FZ] to induce parkinsonism as an adverse effect were evaluated pharmacokinetically and pharmacodynamically in rats. In multiple-dose experiments, CZ or FZ was given to rats at a daily dose of 20 mumol/kg for 1, 5, 10, 15, and 30 days, and CZ, FZ, and the ring-hydroxylated metabolites of their cinnamyl moiety [1-(diphenylmethyl)-4-[3-(4'-hydroxyphenyl)-2-propenyl]piperazine, C-2 and 1-[bis(4-fluorophenyl)methyl]-4-[3-(4'- hydroxyphenyl)propenyl]piperazine, F-2] in the plasma and striatum were determined 24 hr after the final dose. Plasma and striatum concentrations of the above compounds except for FZ reached steady state after 10 doses, but their concentrations of FZ continued to increase throughout the experiments. The concentrations obtained after the 30 doses were in the order of FZ > F-2 > CZ > C-2 for the plasma and of F-2 > FZ > CZ > C-2 for the striatum. The ratios of striatum to plasma concentrations of C-2 and F-2 were 2.4 and 3 times higher than those of the parent drugs. Binding affinities of CZ, FZ, and their 10 metabolites for rat striatal dopamine D-2 receptors (D2-R) were assessed by competitive radioligand-binding studies using [3H]-N-[(2RS,3RS)-1-benzyl-2-methyl-3-pyrrolidinyl]-5-chloro-2-met hoxy- 4-methylamino-benzamide ([3H]-YM-09151-2). The IC50s calculated from their Ki values were in the order of F-2 < C-2 < FZ < CZ < C-4 << F-1, indicating that C-2 and F-2 exhibit higher affinities for D2-R than the parent drugs, whereas affinities of other metabolites were 1 to 2 orders of magnitude less than those of C-2 and F-2. These results suggest some important roles of C-2 and F-2 in the development of parkinsonism as active metabolites during chronic medication with CZ and FZ, respectively.

Flunarizine of limited value in children with intractable epilepsy

Fourteen ambulatory children and adolescents with intractable epilepsy were studied in an open phase II study to investigate the pharmacokinetics and pharmacodynamics of flunarizine as an add-on treatment. Flunarizine was given in increasing doses starting with 0.1-0.3 mg/kg/day until effect was observed or a steady-state plasma concentration of 50-60 ng/ml was reached. Treatment was continued for 3 months at steady state. Pharmacokinetics were determined during the immediate posttreatment period. Positive antiepileptic effect (> or = 50% reduction in seizure frequency) was observed in 4 of 14 patients (29%; 95% CI: 52-5). Independently of antiepileptic effect, 10 of 14 parents (71.4%; 95% CI: 95-48) observed positive cognitive effects. In all patients treatment was withdrawn due to either lack of effect or weight gain. Flunarizine was rapidly absorbed; mean time of peak concentration (Tmax) was 2.7 hours (range: 1-8). The mean terminal half-life was 23.2 days (range: 7-48), the total plasma clearance of flunarizine per fraction of the dose absorbed (CLp/F) was 0.28 ml/min/kg (range: 0.07-042), and the volume of distribution of flunarizine per fraction of the dose absorbed (Vd/F) was 187 L/kg (range: 99-348). We conclude that flunarizine (0.1-0.3 mg/kg/day) seems to be of limited antiepileptic value in children with intractable epilepsy. The pharmacokinetic profile of flunarizine complicates its clinical use.

The effects of a purified toxic extract of Prymnesium patelliferum on transport of ions through the plasma membrane of synaptosomes

Extract of the ichthyotoxic marine alga Prymnesium patelliferum has been shown to have several different effects on the transport of neurotransmitters across nerve membranes. It inhibits the sodium dependent uptake of L-glutamate and GABA and enhances the calcium-dependent release of acetylcholine. We have therefore investigated the effects of a purified toxic extract of P. patelliferum on some membrane properties using rat brain synaptosomes. We found that under conditions where the algal extract inhibited the uptake of L-glutamate, it increased the intracellular concentrations of Na+ and Ca2+, stimulated efflux of K+ determined as 86Rb efflux, and depolarized the synaptosomal membrane. There was no effect on Na+/K(+)-ATPase or ouabain-insensitive ATPase activities. Further, there was no leakage of the cytosolic marker LDH, indicating that the various effects of the algal extract were not due to nonspecific leakage or lysis of the synaptosomes. The rise in the cytosolic concentration of free Ca2+ induced by the algal extract was dependent on extracellular Ca2+, and was inhibited by flunarizine (1-100 microM) but not by the Ca2+ channel blockers omega-conotoxin GVIA (1 microM), diltiazem (100 microM), nifedipine (100 microM) or verapamil (100-500 microM). The increase in Na+ influx induced by the algal extract was insensitive to tetrodotoxin (3 microM) and procaine (100 microM), whereas both the Na+ influx and the membrane depolarization were inhibited by flunarizine (1-100 microM). The increase in K+ efflux was insensitive to flunarizine (5-100 microM). From these results it appears that the toxic extract of P. patelliferum increases the permeability of synaptosomes to Ca2+, Na+ and K+ and that these effects may be responsible for the plasma membrane depolarization and the disturbance of the neurotransmitter transport processes.

Clobazam, oxcarbazepine, tiagabine, topiramate, and other new antiepileptic drugs

Clinical investigators recently have studied at least 21 new antiepileptic drugs (AEDs) in people with epilepsy. This review briefly examines 15 of these new AEDs: clobazam (CLB), dezinamide, flunarizine (FNR), loreclezole, milacemide (MLM), MK-801, nafimidone, ORG-6370, oxcarbazepine (OCBZ), progabide (PGB), ralitoline, stiripentol, tiagabine (TGB), topiramate (TPM), and zonisamide (ZNS). CLB, PGB, and TGB represent agents that act on the GABA system, and MLM acts on the glycine system. MK-801 and ZNS (in part) are excitatory amino acid antagonists, and FNR is a calcium-channel antagonist. OCBZ is a keto analogue of carbamazepine, which is not metabolized to the epoxide and may have fewer side effects. The remaining agents are novel compounds with a variety of suspected mechanisms. TPM appears especially effective for intractable partial seizures but has a high incidence of cognitive side effects. None of these new AEDs is useful for all patients with inadequate seizure control or ongoing toxicity. The role of each will require further clinical study and experience.

Dotarizine versus flunarizine as calcium antagonists in chromaffin cells

1. Dotarizine is a novel piperazine derivative structurally related to flunarizine that is currently being evaluated in clinical trials for its antimigraine and antivertigo effects. This clinical profile may be related to its Ca2+ antagonist properties. Therefore, the actions of both compounds as calcium antagonists were compared in bovine chromaffin cells. 2. Dotarizine and flunarizine blocked 45Ca2+ uptake into K+ depolarized chromaffin cells (70 mM K+/0.5 mM Ca2+ for 60 s) in a concentration-dependent manner, with IC50s of 4.8 and 6.7 microM, respectively. 3. Dotarizine and flunarizine also inhibited the whole-cell Ca2+ and Ba2+ currents (ICa, IBa) in voltage-clamped chromaffin cells, induced by depolarizing test pulses to 0 mV, during 50 ms, from a holding potential of -80 mV. Blockade exhibited IC50s of 4 microM for dotarizine and 2.2 microM for flunarizine. Dotarizine increased the rate of inactivation of ICa and IBa; inhibition of whole-cell currents was use-dependent. 4. Transient increases of the cytosolic Ca2+ concentration, [Ca2+]i, produced by K+ stimulation (70 mM K+ for 5 s) of single fura-2-loaded chromaffin cells, were also inhibited by dotarizine and flunarizine with IC50s of 1.2 and 0.6 microM, respectively. Upon washout of dotarizine, the [Ca2+]i increases recovered fully after 5-10 min. In contrast, the responses remained largely inhibited 10 min after washing out flunarizine. 5. Catecholamine release induced by K+ stimulation (10-s pulses of 70 mM) was inhibited by dotarizine with an IC50 of 2.6 microM and by flunarizine with an IC50 of 1.2 microM. The blocking effects of both compounds developed slowly, and was fully established after 20-30 min of superfusion. While blockade by dotarizine quickly reversed upon its washout, that of flunarizine lasted even 25 min after washing out.6. Catecholamine release from electroporated chromaffin cells triggered by 10 micro M Ca2+ was not affected by 10 micro M dotarizine or flunarizine.7. Overall, the results suggest that dotarizine behaves as a Ca2+ antagonist in bovine chromaffin cells. It exhibits a potency similar to flunarizine in blocking Ca2+ entry, Ca2+ channels, Cai2+ signals and secretion. The dotarizine effects are readily reversible suggesting that in contrast to flunarizine, it does not accumulate in cells. Dotarizine is devoid of intracellular effects on the secretory machinery. All its blocking effects on Ca2+ entry, [Ca2+]i rise and secretion are probably due to blockade of various Ca2+channel subtypes in chromaffin cells. This blockade is use-dependent and seems to be due to the increase by dotarizine of the rate of Ca2+ channel inactivation.

New anticonvulsant drugs. Focus on flunarizine, fosphenytoin, midazolam and stiripentol

In the past decade, several new antiepileptic drugs have been tested. Most recently, 5 new antiepileptic drugs have been launched onto European and US markets. These include vigabatrin, oxcarbazepine and lamotrigine in Europe, and felbamate and gabapentin in the US. In addition to these, 3 additional drugs are in the clinical investigational stage: flunarizine, fosphenytoin and stiripentol. A fourth agent is midazolam, which was originally introduced in 1986, but recently has shown effectiveness in the treatment of status epilepticus. Flunarizine is a selective calcium channel blocker that has shown anticonvulsant properties in both animal and human studies. It is a long-acting anticonvulsant that clinical studies have shown to have effects similar to those of phenytoin and carbamazepine in the treatment of partial, complex partial and generalised seizures. Fosphenytoin was developed to eliminate the poor aqueous solubility and irritant properties of intravenous phenytoin. It is rapidly converted to phenytoin after intravenous or intramuscular administration. In clinical studies, this prodrug showed minimal evidence of adverse events and no serious cardiovascular or respiratory adverse reactions. It may have a clear advantage over the present parenteral formulation of phenytoin. Midazolam is a benzodiazepine that is more potent than diazepam as a sedative, muscle relaxant and in its influence on electroencephalographic measures. It has been shown to be an effective treatment for refractory seizures in status epilepticus. Stiripentol has anticonvulsant properties as well as the ability to inhibit the cytochrome P450 system. There are significant metabolic drug interactions between stiripentol and phenytoin, carbamazepine and phenobarbital (phenobarbitone). Stiripentol has been studied in patients with partial seizures, refractory epilepsy and refractory absence seizures with some efficacious results.

Drug-induced parkinsonism: a review

The main clinical features, pathophysiology and underlying mechanisms of drug-induced parkinsonism are reviewed. The clinical manifestations of drug-induced parkinsonism are often indistinguishable from idiopathic Parkinson's disease. However, some subtle differences may exist: for example drug-induced parkinsonism is often associated with tardive dyskinesias, bilateral symptoms and the absence of resting tremor, etc. Besides toxins (eg manganese, carbon monoxide or MPTP), many drugs are known to produce parkinsonism: dopamine blocking drugs (true neuroleptics used as antipsychotics: phenothiazines, butyrophenones, thioxanthenes but also sulpiride, "hidden" neuroleptics prescribed as anti-nausea or anti-vomiting drugs (such as metoclopramide and other benzamide derivatives), dopamine depleting drugs (reserpine, tetrabenazine), alpha-methyldopa, calcium channel blockers (flunarizine, cinnarizine, etc). The putative role of other drugs (eg fluoxetine, lithium, amiodarone) as well as the therapeutic management of this side effect are reviewed.

Drug-induced depression. Incidence, avoidance and management

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R), drug-induced depression may be classified as an Organic Mood Syndrome, Depressed Type. Unfortunately, the DSM-III-R diagnostic criteria are not sufficiently precise for application in research, and studies of drug-induced depression have rarely utilised these criteria. Research concerned with drug-induced depression is characterised by a number of methodological complications. These include differing definitions of depression, including depression defined as a symptom, a syndrome, or by diagnostic criteria for a specific mental disorder. In addition, patients undergoing pharmacological treatments for medical illnesses are typically exposed to considerable psychosocial stress due to the suffering and disability associated with illness. These psychosocial factors may in themselves precipitate episodes of depression. Due to these complicating factors, sophisticated study designs are required to confirm an aetiological role for medications as risk factors for depression. Unfortunately, adequate studies have rarely been conducted, and much of the literature consists of case reports and clinical observations. Consequently, clinicians are frequently required to make clinical judgements about the aetiology of patients' depressive symptoms in the absence of definitive scientific information about the role of drugs. Nevertheless, a knowledge of the relevant literature will assist clinicians in making reasoned judgements about the aetiology, prevention and management of these disorders.

Effects of dotarizine on 45Ca2+ movements and contractile responses in vascular smooth muscle

The inhibitory effects of dotarizine on 45Ca2+ movements and contractile responses were studied and compared, using the same parameters measured in rabbit aorta and basilar smooth muscle. Dotarizine 10(-9)-10(-5) M inhibited the contractile responses induced by high K+ (80 mM), noradrenaline (10(-6) M) or 5-hydroxytryptamine (5-HT, 10(-5) M). These effects were observed when dotarizine was added before or after the induced contractions and were more potent in basilar arteries than in aorta. Moreover, dotarizine at concentrations less than 10(-6) M did not modify the contractile response obtained in aorta rings. Contractile responses induced by the addition of Ca2+ to Ca(2+)-free high-K+ solution were also concentration dependently inhibited by dotarizine 10(-7)-10(-6) M in aorta and basilar arteries. Dotarizine also inhibited the contractile response induced by caffeine (20 mM) in aortic rings incubated in normal or in Ca(2+)-free medium. Dotarizine reduced the 45Ca(2+) uptake stimulated by high K+, noradrenaline or 5-HT even in the aorta or basilar artery, but the inhibition was greater in basilar arteries than in aorta. These results suggest that, in rabbit, dotarizine inhibits Ca2+ entry through Ca2+ channels, being more selective for the basilar artery, probably by acting on multiple sites to decrease the availability of intracellular free Ca2+ required for activation.

Binding of the calcium antagonist flunarizine to phosphatidylcholine bilayers: charge effects and thermodynamics

We have examined the partitioning/transfer of the Ca2+ antagonist flunarizine from the aqueous phase into phospholipid bilayers. We show that the binding of the cationic amphiphilic drug flunarizine to phospholipid bilayers displays traditional linear concentration-dependent characteristics once unmasked of electrostatic effects. The coefficient for the binding/partitioning of flunarizine to phosphatidylcholine was found to be 28700 M-1, supporting the notion that this drug may be particularly membrane-active. The thermodynamics of the partitioning/transfer process have also been studied using high-sensitivity titration calorimetry. Binding was found to be predominantly enthalpy-driven with only a small entropic contribution; delta H = -22.1 kJ.mol-1 (-5.3 kcal.mol-1) at 27 degrees C. This is in conflict with established ideas of entropy-driven partitioning of drugs into phospholipid membranes as a result of the 'hydrophobic effect'. The strong enthalpic nature of binding is interpreted as being indicative of strong lipophilic interactions between the drug and the phospholipid phase.

Virus-induced airway hyperresponsiveness in the guinea-pig: possible involvement of histamine and inflammatory cells

1. Guinea-pig tracheal contractions by histamine and by the cholinoceptor agonist, arecoline, are significantly enhanced (30% and 20%, respectively), 96 h after intra-tracheal inoculation with Parainfluenza-3 (PI-3) virus. 2. The airway hyperresponsiveness in animals inoculated with virus coincides with a significant increase in the number of broncho-alveolar cells (82%), and in the albumin concentration (121%) in lung lavage fluid, relative to values obtained in guinea-pigs challenged with control solution. 3. The chemiluminescence production by isolated broncho-alveolar cells, obtained from virus-infected guinea-pigs 96 h after inoculation stimulated with PI-3 virus in vitro, is significantly reduced by 42% relative to broncho-alveolar cells obtained from animals inoculated with control solution. This diminution was not specific for stimulation by PI-3 virus since the chemiluminescence production was also significantly reduced by 30% in response to zymosan. 4. Pretreatment of the guinea-pigs with the anti-allergic drugs, oxatomide (2.5 mg kg-1) or nedocromil (2.5 mg kg-1), or the specific H1-histamine receptor antagonist, levocabastine (0.25 mg kg-1), administered intra-peritoneally twice a day for five successive days, inhibits the virus-induced airway hyperresponsiveness, suppresses the influx of broncho-alveolar cells and increase in albumin content, and corrects the reduced chemiluminescence production by broncho-alveolar cells in response to zymosan. 5. In contrast, the cyclo-oxygenase inhibitor, suprofen (5.0 mg kg-1), the 5-HT2 receptor antagonist, ketanserin (0.63 mg kg-1), or the Ca2+ overload blocker, flunarizine (2.5 mg kg-1) do not modify the above mentioned processes. 6. The platelet-activating factor receptor antagonist, WEB 2170 (10 mg kg-1), reduces virus-induced airway hyperresponsiveness and influx of broncho-alveolar cells into the lungs but does not attenuate the increase of albumin in the bronchial lavage fluid. 7. Guinea-pigs nebulized with histamine, twice a day (30 min) during 4 successive days, do not demonstrate an increased airway responsiveness, but instead show tachyphylaxis in response to histamine in vitro. In addition, no influx of inflammatory cells is found in these animals. 8. These results suggest that histamine does not directly increase the responsiveness of the guinea-pig trachea; however, histamine may be involved in a cascade of events leading to airway hyperresponsiveness after a viral infection, a process that could be related to an influx and/or an activation of broncho-alveolar cells after PI-3 virus stimulation.