Formulation design and in vitro ex vivo evaluation of transdermal patches of Cinnarizine.

The aim of this study was to develop a Transdermal patch containing Cinnarizine using different ratios of hydrophilic and hydrophobic polymeric systems by solvent evaporation technique employing Polyethylene glycol (PEG 400) as plasticizer. The physicochemical compatibility of the drug and the polymers were studied by performing FT-IR spectroscopic analysis. Formulated patches were evaluated for physicochemical properties, skin irritation, in vitro drug release, ex-vivo permeation studies across rat abdominal skin and stability studies. The results of FT-IR studies revealed that there were no interactions between drug and polymers used. All the formulations exhibited uniformity in physicochemical properties. In vitro permeation studies of the formulations were performed by using Franz diffusion cells. Formulation F3 showed better permeation through rat skin (i.e., 8527.5±1.25µ/cm2 /hr) compared to rest of formulations and followed Fick's diffusion mechanism. On the basis of in-vitro drug release and ex-vivo skin permeation performance, Formulation F3 containing the polymeric blend 19:1 Hydroxypropylmethyl Cellulose (HPMC E 50cps: Eudragit RL 100) has shown optimum release in comparison to other formulations and indicated good physical stability. So it has been demonstrated that Cinnarizine can be designed as matrix type transdermal drug delivery system (TDDS) and further in-vivo evaluations were required.

Zebrafish (Danio rerio) embryos as a model for testing proteratogens.

Zebrafish embryos have been shown to be a useful model for the detection of direct acting teratogens. This communication presents a protocol for a 3-day in vitro zebrafish embryo teratogenicity assay and describes results obtained for 10 proteratogens: 2-acetylaminofluorene, benzo[a]pyrene, aflatoxin B(1), carbamazepine, phenytoin, trimethadione, cyclophosphamide, ifosfamide, tegafur and thio-TEPA. The selection of the test substances accounts for differences in structure, origin, metabolism and water solubility. Apart from 2-acetylaminofluorene, which mainly produces lethal effects, all proteratogens tested were teratogenic in zebrafish embryos exposed for 3 days. The test substances and/or the substance class produced characteristic patterns of fingerprint endpoints. Several substances produced effects that could be identified already at 1 dpf (days post fertilization), whereas the effects of others could only be identified unambiguously after hatching at ≥ 3 dpf. The LC50 and EC50 values were used to calculate the teratogenicity index (TI) for the different substances, and the EC20 values were related to human plasma concentrations. Results lead to the conclusion that zebrafish embryos are able to activate proteratogenic substances without addition of an exogenous metabolic activation system. Moreover, the teratogenic effects were observed at concentrations relevant to human exposure data. Along with other findings, our results indicate that zebrafish embryos are a useful alternative method for traditional teratogenicity testing with mammalian species.

Effect of route of administration on the pharmacokinetics and toxicokinetics of cinnarizine in dogs.

AIMS: Cinnarizine, a piperazine derivative, is currently used for the treatment of cerebral thrombosis, cerebral arteriosclerosis, subarachnoid hemorrhage and some other diseases. However, it exhibits variable dissolution and low bioavailability after oral administration. Cinnarizine for injection was developed in order to enhance its bioavailability and make the practice more convenient for patients suffering from dysphagia. The aim of the present study was to compare the pharmacokinetics and toxicokinetics of cinnarizine following intravenous and oral administration in dogs and provide scientific basis for the development of cinnarizine for injection. METHODS: Beagle dogs were given single- or multiple-dose of cinnarizine by oral (single-dose: 10mg/kg; multiple-dose: 21.5, 12.9, 4.3mg/kg) and intravenous (single-dose: 10mg/kg; multiple-dose: 10, 6, 2mg/kg) routes. HPLC was applied to detect the plasma concentration of cinnarizine. The pharmacokinetics and toxicokinetics parameters were calculated and compared. RESULTS: The pharmacokinetics of cinnarizine following oral administration in dogs was found to fit the one-compartment mode. That of cinnarizine following intravenous injection in dogs was found to fit the two-compartment model. The relative bioavailability of oral administration was 46.4%. Cinnarizine cumulated significantly in dogs when 10mg/kg cinnarizine was injected repeatedly. Multiple-dose of cinnarizine over 6mg/kg induced reversible kidney injury in dogs. CONCLUSION: The present study indicates that pharmacokinetics and toxicokinetics properties of cinnarizine for injection show advantages over the oral preparation. But caution should be taken with the cumulative action when cinnarizine is injected and the dose of cinnarizine should be lower than 6mg/kg.

Acute toxicity and toxicokinetics of dipfluzine hydrochloride, a novel calcium channel blocker.

Dipfluzine hydrochloride, diphenylpiperazine calcium channel blocker, is a promising candidate to treat ischemic stroke. The purpose of the study is to evaluate the acute toxicity and toxicokinetics of dipfluzine hydrochloride after single intravenous doses in rats. Acute toxicity study was performed in rats at doses of 5, 6, 10, 15, 25, 30, 35, and 40mg/kg. Concentrations of dipfluzine in plasma and tissues were determined with a reverse-phase HPLC method after single doses of 5, 15 and 30mg/kg. The results demonstrated that no-observed-adverse-effect level (NOAEL), lowest-observed-adverse-effect level (LOAEL), maximal tolerance dose (MTD), and minimal lethal dose (MLD) were respectively 5, 6, 30, 35mg/kg for i.v. administration of dipfluzine hydrochloride. The toxicokinetic study revealed that the severity of toxicity was linear with the level of systemic exposure. The highest tissue exposure was detected in lung tissue and it may primarily contribute to the pulmonary congestion in dead rats. Longer elimination half-lives of dipfluzine in kidney, brain, liver, and pancreas imply a possible accumulation of dipfluzine in these tissues for long-term exposure. In addition, a temporary impairment in liver and heart was observed for clinical chemistry in 30mg/kg dose group. The findings will help to design further studies to characterize the repeat-dose toxicity of dipfluzine hydrochloride.

Quantitative prediction of catalepsy induced by amoxapine, cinnarizine and cyclophosphamide in mice.

Parkinsonism can be a side effect of antipsychotic drugs, and has recently been reported with peripherally acting drugs such as calcium channel blockers, antiarrhythmic agents and so on. In this study, we examined the quantitative prediction of drug-induced catalepsy by amoxapine, cinnarizine and cyclophosphamide, which have been reported to induce parkinsonism. Dose-dependent catalepsy was induced by these drugs in mice. In vivo dopamine D(1), D(2) and muscarinic acetylcholine (mACh) receptor occupancies by these drugs in the striatum were also examined. The in vitro binding affinities (K(i) values) of amoxapine and cinnarizine to dopamine D(1), D(2) and mACh receptors in rat striatal synaptic membrane were 200 and 2900 nM, 58.4 and 76.4 nM and 379 and 290 nM, respectively. Cyclophosphamide did not bind to these receptors at concentrations up to 100 microM. Twenty drugs, including those mentioned above, showed a significant correlation between the observed intensity of catalepsy and the values predicted with a pharmacodynamic model (Haraguchi K, Ito K, Kotaki H, Sawada Y, Iga T. Prediction of drug-induced catalepsy based on dopamine D(1), D(2), and muscarinic acetylcholine receptor occupancies. Drug Metab Disp 1997; 25: 675-684) based on in vivo occupancy of dopamine D(1), D(2) and mACh receptors. We conclude that occupancy of dopamine D(1) and D(2) receptors contributes to catalepsy induction by amoxapine and cinnarizine.

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.

Inhibition of steroid sex hormones release in rats by two Ca2+ channel blockers.

The calcium channel blockers Diltiazem HCl (2 mg kg-1 day-1, IP) or Cinnarizine (8 mg kg-1 day-1, IP) were given for a period of 30 days to adult male and female albino rats. The effect of each calcium channel blocker on circulating blood levels of steroid sex hormones was investigated by radioimmunoassay in comparison with the normal control level. The data demonstrated that both Diltiazem and Cinnarizine significantly decreased serum normal testosterone levels in males (36% and 52% inhibition respectively) as well as both normal estradiol and progesterone contents in females (58% and 45% inhibition with Diltiazem and 68% and 52% inhibition with Cinnarizine respectively). This study indicates the importance of blood sex hormones-follow up in case of long term Ca2+ channel blockers medication.

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.

Acute toxicity of dipfluzine and its effects on isolated vascular smooth muscle.

Dipfluzine (Dip) is a new derivative of cinnarizine (Cin) first developed by Department of Chemistry, Beijing University. Dip showed a dose-dependently inhibitory effect on both KCl- and NE-induced contraction in the rabbit aortic rings. It was more effective in suppressing the contractile response evoked by KCl than that by NE. Dip also inhibited the KCl-induced contraction in porcine basilar, coronary and radial arteries. Their pD2' values were 5.7 +/- 0.6, 5.4 +/- 0.4 and 4.6 +/- 0.5 respectively. The selectivity of Dip for vasodilation was proved by higher pD2' value of the basilar artery than that of the coronary and radial arteries, and this selectivity of Dip was more significant than that of Cin. The acute iv LD50 of Dip and Cin in mice were 37 and 36 mg/kg, respectively.

Flunarizine. A review of its pharmacodynamic and pharmacokinetic properties and therapeutic use.

Flunarizine is a 'selective' calcium entry blocker with a similar chemical structure and pharmacological profile to the related compound, cinnarizine. However, in contrast to cinnarizine it has a long plasma half-life and need only be given once a day. The majority of therapeutic trials in the prophylaxis of migraine, occlusive peripheral vascular disease and vertigo of central or peripheral origin have been placebo-controlled, and have shown that the drug produces significantly greater beneficial effects than placebo as evaluated by subjective and objective criteria. A small number of comparative studies have shown flunarizine to be at least as effective as pizotifen in migraine prophylaxis, and in a longer term study as effective as cinnarizine in vertigo of central origin. However, it has not been compared with other drugs which may be useful in these areas, such as methysergide in migraine prophylaxis, some antihistamines or phenothiazines in vertigo, or (understandably at this stage of its evolution) with surgical revascularisation in severe occlusive peripheral vascular disease. In preliminary placebo-controlled studies there was some evidence that flunarizine may improve impaired cognitive function in patients with cerebrovascular disorders, but such findings need further confirmation in additional carefully conducted studies. With a very long half-life, flunarizine may be given once daily; and drowsiness, the main side effect, can be minimised by taking the daily dose in the evening. Thus, it appears that flunarizine will offer a useful alternative in some therapeutic areas that can be difficult to manage with previously available therapy. However, a definitive statement on its relative place in therapy of such conditions must await a few well-controlled comparative studies.

Determinación del índice terapéutico de la cinaricina, la difenhidramina y el ketotifeno / Determination of cinnarizine, diphenhydramine, and ketotifen therapeutical index

Se calculó el indice terapéutico (IT) de la cinaricina (Cin), la difenhidramina (Dif) y el ketotifeno (Ket). La curva de letalidad se determinó en ratones y la de efectividad en cobayos sometidos a un aerosol de histamina. Los resultados se procesaron por el método de Litchfield y Wilcoxon (1949). El IT calculado según la fórmula DL 1/DE 99 fue de 0,44, 1,17 y 30,2, respectivamente para la Cin., la Dif. y el Ket. Se concluyó que el Ket. fue el antihistamínico más efectivo, con un gran margen de seguridad con respecto a las dosis letales. La Dif. ocupó una posición intermedia, en tanto que el margen de seguridad de la Cin. fue nulo, ya que se superpusieron las dosis tóxicas mínimas con las dosis efectivas máximas (AU)

Anticonvulsive properties of cinnarizine and flunarizine in rats and mice.

The anticonvulsive properties of orally administered cinnarizine [(E)-1-(diphenylmethyl)-4-(3-phenyl-2-propenyl)-piperazine], its difluoro derivative flunarizine [(E)-1-(bis-(4-fluorophenyl)methyl)-4-(3-phenyl-2-propenyl)-piperazine], diphenylhydantoin and phenobarbital, were studied against maximal metrazol seizures (MMS) in rats and maximal electroshock seizures (MES) in mice. In rats (MMS), the lowest ED50 for protection against tonic extension of hindpaws was 4.10 mg/kg (1 h 35 min after treatment) with sodium phenobarbital, 6.04 mg/kg (5 h 45 min) with flunarizine dihydrochloride, 9.84 mg/kg (2 h 34 min) with cinnarizine and 19.30 mg/kg (3 h 38 min) with diphenylhydantoin. In mice (MES), protection against tonic extension of hindpaws was (2 h after treatment) 7.0 mg/kg with diphenylhydantoin, 13.2 mg/kg with sodium phenobarbital, 20.9 mg/kg with flunarizine kihydrochloride and 49.0 mg/kg with cinnarizine. Except at subtoxic doses no side effects were observed in rats and mice given cinnarizine, flunarizine kihydrochloride or kiphenylhydantoin. Phenobarbital induced ataxia in rats and mice at 22 mg/kg and 42.7 mg/kg, respectively, and loss of righting reflex at 112.8 mg/kg and 160 mg/kg, respectively. Flunarizine is the longest-acting drug and has the slowest onset. At a dose of twice the minimal ED50 flunarizine affords protection against tonic extension of hindpaws in rats (MMS) for 23 h 30 min dephenylhydantoin for 11 h 38 min, phenobarbital for 8 h 22 min and cinnarizine for 8 h 16 min. Peak effect was reached with flunarizine at 5 h 45 min, with diphenylhydantoin at 3 h 38 min, with cinnarizine at 2 h 34 min and with phenobarbital at 1 h 35 min. The anti-MMS profiles of cinnarizine and flunarizine resemble that of dephenylhydantoin as all three compounds are selective blockers of tonic extension of hindpaws. Phenobarbital antagonized the whole MMS-pattern, i.e., tremors, clonic convulsions and tonic extension of fore- and hindpaws. However, the effects of phenobarbital against tremors, clonic convulsions and tonic extension of forepaws may reflect more a general CNS-depressant effect than a specific anticonvulsive activity since neurotoxic effects (ataxia and loss of righting reflex) appear at the same doses.