Pharmacokinetics, pharmacodynamics and clinical use of trazodone and its active metabolite m-chlorophenylpiperazine in the horse

Trazodone is a serotonin receptor antagonist and reuptake inhibitor used extensively as an anxiolytic in human and small animal veterinary medicine. The aims of this study were to determine the pharmacokinetics of oral trazodone in experimental horses and to evaluate the effect of oral trazodone in clinical horses. Six experimental horses were administered trazodone at 7.5 or 10 mg/kg. Plasma concentrations of trazodone and its metabolite (m-CPP) were determined via UPLC-MS/MS. Noncompartmental pharmacokinetic analysis, sedation and ataxia scores were determined. Trazodone was rapidly absorbed after oral administration with a maximum concentration of 2.5-4.1 μg/ml and half-life of the terminal phase of approximately 7 hr. The metabolite was present at low levels in all horses, representing only 2.5% of the total area under the curve. In experimental horses, concentration-dependent sedation and ataxia were noted, lasting up to 12 hr. For clinical cases, medical records of horses treated with trazodone for various abnormal behaviours were reviewed and data were summarized. Trazodone was successful in modifying behavioural problems to some degree in 17 of 18 clinical cases. Tolerance and subsequent lack of drug effect occurred in two of 18 clinical cases following 14 or 21 days of use. In both populations of horses, adverse effects attributed to trazodone include oversedation, muscle fasciculations and transient arrhythmias.

Isobolographic analysis of the cutaneous antinociceptive interaction between bupivacaine co-injected with serotonin in rats

BACKGROUND

The aim of this experiment was to investigate a long-lasting local anesthetic bupivacaine combined with serotonin at inducing cutaneous antinociception.

METHODS

The skin antinociception, characterized by an inhibition of the cutaneous trunci muscle reflex (CTMR) following the pinprick on the dorsal skin of rats, was evaluated. The cutaneous antinociceptive effects of bupivacaine alone, serotonin alone, or bupivacaine co-injected with serotonin in a dose-dependent fashion were constructed, while the drug-drug interactions were evaluated by isobologram.

RESULTS

Subcutaneous serotonin, as well as the local anesthetic bupivacaine provoked dose-related cutaneous antinociception. On an equipotent basis (50% effective dose [ED₅₀]), the relative potency was bupivacaine (0.43 [0.37-0.50] μmol)>serotonin (1.27 [1.15-1.40] μmol) (p<0.01). At the equi-anesthetic doses (ED₇₅, ED₅₀ and ED₂₅), the duration of bupivacaine was similar to that of serotonin at producing cutaneous antinociceptive effects. Co-administration of bupivacaine and serotonin displayed a synergistic antinociception.

CONCLUSIONS

The preclinical data demonstrated that serotonin is less potent in eliciting cutaneous antinociceptive effects but has the similar duration of action, compared with bupivacaine. We also found a more significant depth of the sensory block with bupivacaine+serotonin than bupivacaine alone.

Cerebellar heterogeneity and its impact on PET data quantification of 5-HT receptor radioligands

In the quantification of positron emission tomography (PET) radiotracer binding, a commonly used method is reference tissue modeling (RTM). RTM necessitates a proper reference and a ubiquitous choice for G-protein coupled receptors is the cerebellum. We investigated regional differences in uptake within the grey matter of the cerebellar hemispheres (CH), the cerebellar white matter (CW), and the cerebellar vermis (CV) for five PET radioligands targeting the serotonin system. Furthermore, we evaluated the impact of choosing different reference regions when quantifying neocortical binding. The PET and MR images are part of the Cimbi database: 5-HT1AR ([11C]CUMI-101, n = 8), 5-HT1BR ([11C]AZ10419369, n = 36), 5-HT2AR ([11C]Cimbi-36, n = 29), 5-HT4R ([11C]SB207145, n = 59), and 5-HTT ([11C]DASB, n = 100). We employed SUIT and FreeSurfer to delineate CV, CW, and CH and quantified mean standardized uptake values (SUV) and nondisplaceable neocortical binding potential (BPND). Statistical difference was assessed with paired nonparametric two-sided Wilcoxon signed-rank tests and multiple comparison corrected via false discovery rate. We demonstrate significant radioligand specific regional differences in cerebellar uptake. These differences persist when using different cerebellar regions for RTM, but the influence on the neocortical BPND is small. Nevertheless, our data highlight the importance of validating each radioligand carefully for defining the optimal reference region.

A Comparison of the Pharmacokinetics and Tolerability of the Anti-Migraine Compound Almotriptan in Healthy Adolescents and Adults

This study was designed to assess and compare the pharmacokinetics and tolerability of almotriptan, a 5-HT1B/1D agonist used to treat migraine attacks, in adolescents and adults. Healthy adolescents ( n = 18) and adults ( n = 18) received a single 12.5-mg dose of almotriptan after fasting overnight. Plasma and urinary almotriptan concentrations were measured by high-performance liquid chromatography. Pharmacokinetic parameters of almotriptan were determined by non-compartment analysis. The 90% confidence interval (CI) approach was employed to assess age effects. Mean Cmax, tmax, area under the curve (AUC 0-∞), half-life, and percentage excreted in urine were nearly identical for the two populations. Mean oral (CLPO) and renal (CLR) clearances were similar between the age groups; however, weight-corrected CLPO was approximately 32% higher (90% CI 16, 51) in adolescents compared with adults. The higher weight-corrected CLPO appeared to offset increases in exposure expected on the basis of lower body weight in adolescents. The findings were the same when a subgroup ( n = 9) of 12-14-year old children was compared with adults. The type, incidence and severity of adverse events were similar between the two age groups and were consistent with those reported previously during adult clinical trials. Based on these pharmacokinetic and tolerability findings, no dose adjustment for almotriptan would be required when treating patients as young as 12 years old.

Pharmacokinetic and Pharmacodynamic Variability as Possible Causes for Different Drug Responses in Migraine. A Comment

The pharmacokinetics of antimigraine drugs zolmitriptan and sumatriptan varied considerably with a fourfold to 10-fold variation in plasma levels. In addition, the pharmacodynamics of triptans as investigated in vitro also varied considerably. In theory, there should probably be a 10-fold variation in doses available, but in clinical practice a fourfold difference in doses will probably cover the needs of most patients.

Brain delivery of buspirone hydrochloride chitosan nanoparticles for the treatment of general anxiety disorder

The present work discusses the preparation, characterization and in vivo evaluation of thiolated chitosan nanoparticles (TCS-NPs) of buspirone hydrochloride (BUH) for brain delivery through intranasal route. TCS NPs were prepared by ionic gelation method and characterized for various parameters. The NPs formed were having particle size of 226.7±2.52nm with PDI 0.483±0.031. Drug entrapment efficiency (EE) and loading capacity (LC) were found to be 81.13±2.8 and 49.67±5.5%. The cumulative percentage drug permeation through nasal mucosa was 76.21%. Bioadhesion study carried out on porcine mucin and showed a bioadhesion efficiency of 90.218±0.134%. Nose-to-brain delivery of placebo NPs was investigated by confocal laser scanning microscopy (CLSM) technique using rhodamine-123 as a marker. The brain concentration achieved after intranasal administration of TCS-NPs was 797.46±35.76ng/ml with tmax 120min which was significantly higher than achieved after intravenous administration on BUH solution 384.15±13.42ng/ml and tmax of 120min and intranasal administration of BUH solution 417.77±19.24ng/ml and tmax 60min.

Zolmitriptan (Zomig®)

New triptans are being released in rapid succession with each addition demonstrating some specific pharmacokinetic properties, which may be translated into clinical advantages. Zolmitriptan (Zomig) offers a range of alternatives to migraine sufferers. The conventional tablet is consistently effective across a wide range of migraine subtypes. The orally disintegrating tablet offers an effective option for those migraineurs who are nauseated or need to take their medication earlier in the course of their migraine. Since it can be taken without fluid, the orally disintegrating tablet may be consistently used early in the migraine attack when the pain is still mild. The nasal spray aggregates all the benefits of the oral formulations and has a faster onset of action. The 5-mg dose of all three forms of zolmitriptan offers additional benefits over the 2.5-mg dose at early time points. The physician can now choose the optimum route of delivery of zolmitriptan to stop the headache, increase the likelihood of reducing disability and restore the patient to complete functionality.

Oral almotriptan: practical uses in the acute treatment of migraine

Almotriptan (Almogran, Lundbeck; Almirall Prodesfarma; Axert, Ortho-McNeil) is a novel 5-HT(1B/1D) receptor agonist (triptan) that is widely available on prescription for the acute treatment of migraine. Almotriptan has pharmacodynamic and pharmacokinetic profiles that make it suitable for use in this indication. It is a potent agonist at 5-HT(1B), (1D) and (1F) receptors, while having a low affinity for other 5-HT receptors. It is also a potent inhibitor of neurogenic inflammation. Almotriptan has a high oral bioavailability, is absorbed rapidly, has a relatively short plasma half-life and its route of elimination presents few potential problems. Placebo-controlled dose-finding studies have demonstrated that almotriptan tablets are effective and well-tolerated in the acute treatment of migraine, with a 12.5 mg dose providing the best balance between efficacy and tolerability. Large placebo-controlled studies show that the efficacy of oral almotriptan is comparable with that of the other oral triptans. In direct comparator-controlled studies, almotriptan was as effective as sumatriptan 50 and 100 mg but had a superior tolerability profile. Furthermore, the efficacy and tolerability of almotriptan is sustained in the long term following open-label administration. Meta-analyses and post hoc analyses of clinical data confirm these findings. In conclusion, almotriptan 12.5 mg is a good therapeutic choice for the symptomatic treatment of acute migraine attacks.

Pharmacokinetic Profile of Rizatriptan 10-mg Tablet and 10-mg Orally Disintegrating Tablet Administered With or Without Water in Healthy Subjects: An Open-Label, Randomized, Single-Dose, 3-Period Crossover Study

This open-label, 3-period crossover study compared the plasma concentration profiles of rizatriptan tablet, orally disintegrating tablet with water (ODTc), and ODT without water (ODTs) in 24 healthy volunteers aged 18 to 45 years. At each period, subjects received a single dose of either 10-mg rizatriptan tablet, 10-mg rizatriptan ODTs, or 10-mg rizatriptan ODTc. The authors hypothesized that ODTc has a greater geometric mean AUC(0-2h) than ODTs and that ODTc has a greater geometric mean AUC(0-1h) than tablet. A secondary end point was to compare the time of occurrence of the maximum rizatriptan plasma concentration (t(max)) of each dosing method. ODTc had a statistically significantly greater geometric mean AUC(0-2h) compared with ODTs (33.84 h x ng/mL vs 18.83 h x ng/mL; P < .001). ODTc had a slightly, but not statistically significantly, greater geometric mean AUC(0-1h) compared with rizatriptan tablet (17.07 h x ng/mL vs 13.32 h x ng/mL). The median t(max) was 0.67 hours for ODTc and tablet and 1.33 hours for ODTs. ODTc showed a slightly, but not significantly, faster rate of absorption compared with tablet. ODTs with water had a faster rate of absorption than ODTc. Future studies are needed to determine whether this pharmacokinetic difference produces differential efficacy in a clinical setting.

Bioequivalence study of 2 orodispersible formulations of zolmitriptan 5 mg in healthy volunteers

A bioequivalence study of 2 zolmitriptan (CAS 139264-17-8) orodispersible tablet formulations was carried out in 26 healthy volunteers according to an open label, randomized, 2-period, 2-sequence, crossover, single dose and fasting conditions design. The test and reference formulations were administered in 2 treatment days, separated by a washout period of 7 days. Plasma concentrations of zolmitriptan and its active metabolite (N-desmethyl-zolmitriptan) were obtained by LC/MS/MS method. Log-transformed AUCs and Cmax values were tested for bioequivalence based on the ratios of the geometric means (test/reference). Tmax was analysed nonparametrically. The 90% confidence intervals of the geometric mean values for the test/reference ratios for AUC0-t and Cmax were within the bioequivalence acceptance range of 80-125%. According to the European Guideline 1 it may be therefore concluded that test formulation of zolmitriptan 5 mg orodispersible tablet is bioequivalent to the reference formulation.

Anxiolytic effects of 5-HT₁A receptors and anxiogenic effects of 5-HT₂C receptors in the amygdala of mice

The aim of the present study is to test a hypothesis that 5-HT(1A) and 5-HT(2C) receptors in the amygdala play an important role in the regulation of anxiety behaviors. We examined alterations in anxiety-like behaviors after manipulation of the expression of 5-HT(1A) and 5-HT(2C) receptors in the amygdala using recombinant adenovirus approaches. Recombinant adenoviruses containing a 5-HT(1A) promoter-controlled 5-HT(1A) antisense sequence or a 5-HT(2C) promoter-controlled 5-HT(2C) sense sequence were injected into the amygdala. Elevated plus-maze (EPM) and open field tests were conducted to determine anxiety-like behavior and locomotor activity. Reductions in the expression of 5-HT(1A) receptors in the amygdala significantly attenuated the time spent in the open arms of EPM and time spent in the center of an open field. Reduction in the percent of time spent in the open arms of EPM is negatively correlated with the density of 5-HT(1A) receptors in the central amygdala. On the other hand, increased expression of 5-HT(2C) receptors reduced the time spent in the open arms of EPM and time spent in the center of an open field. The reductions in the time spent and distance traveled in the open arms of EPM were correlated to the density of 5-HT(2C) receptors in the basolateral nucleus of amygdala. These data suggest that amygdaloid 5-HT(1A) receptors produce anxiolytic and 5-HT(2C) receptors produce anxiogenic effects. Together, the present results demonstrate the important role of the amygdaloid 5-HT(1A) and 5-HT(2C) receptors in the regulation of anxiety-like behaviors. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Transdermal delivery of sumatriptan for the treatment of acute migraine

SUMMARY

Migraine is a common, multisymptom disorder that can severely impact the daily activities of migraineurs. Triptans (primarily sumatriptan) are the most commonly prescribed treatment for migraine and are considered a relatively safe and effective initial therapy. Unfortunately, current sumatriptan formulations (i.e., oral, nasal, subcutaneous) may be associated with limitations that can result in patients' delaying or avoiding treatment. For oral formulations, these limitations include difficulty in taking an oral medication due to the nausea and vomiting that often accompany migraine, and inconsistent absorption, whereas nasal and subcutaneous formulations may be associated with low bioavailability and an undesirable rate of adverse events, respectively. An alternative to current formulations is transdermal drug delivery, particularly iontophoresis. Transdermal delivery has several advantages over current formulations, including avoidance of the gastrointestinal tract, controlled and sustained delivery, and convenient administration. This article reviews the in vitro, in vivo, and preclinical data supporting the use of iontophoresis for the delivery of sumatriptan, as well as the recent clinical data for Zelrix (NuPathe Inc., Conshohocken, PA), an iontophoretic sumatriptan patch currently in phase III development for the treatment of migraine.

Studies on 1-arylpiperazine derivatives with affinity for rat 5-HT7 and 5-HT1A receptors

Several 1-aryl-4-(2-arylethyl)piperazine derivatives were synthesized and tested in-vitro for their binding affinity for 5-HT7 and 5-HT1A receptors. These compounds displayed 5-HT7 receptor affinity ranging between Ki = 474 nm and Ki = 8.2 nm, besides high affinity for the 5-HT1A receptor. Intrinsic activity of the most potent compounds was assessed. 4-[2-(3-Methoxyphenyl)ethyl]-1-(2-methoxyphenyl)piperazine (16) and 1-(1,2-benzisoxazol-3-yl)-4-[2-(3-methoxyphenyl)ethyl]piperazine (20) (Ki = 24.5 and 8.2 nm, respectively) behaved as partial agonist and full agonist, respectively, when tested for 5-HT7 receptor-mediated relaxation of substance P-induced guinea-pig ileum contraction.

Transport characteristics of zolmitriptan in a human intestinal epithelial cell line Caco-2

The intestinal absorption characteristics and the efflux mechanisms of zolmitriptan, a new generation and highly selective 5-HT1B/1D receptor agonist used in the acute oral treatment of migraine, were investigated. A human intestinal cell line, Caco-2, was used as an in-vitro model of the intestinal mucosa to assess transepithelial transport of zolmitriptan. In the Caco-2 cells, the absorptive transport of zolmitriptan was pH dependent and the transport was enhanced at weakly alkali pH on the apical side. No concentration dependence and saturation were observed for the apical-to-basolateral and basolateral-to-apical transport of zolmitriptan at a concentration of 0.1–10 mM. The permeability ratio value was about 1.5-2.6 at a concentration of 0.1–2.0 mM. Inhibition experiments using verapamil, nifedipine and nimodipine as inhibitors were studied and indicated that P-glycoprotein participated in the transport of zolmitriptan. Inhibition of the Na+-H+ exchanger with amiloride resulted in a significant increase in absorption and a slight inhibition in secretion. This suggests that the Na+-H+ exchanger may be involved in the transport of zolmitriptan. The results indicated that the transport of zolmitriptan was mediated by both passive diffusion and active transport. A series of drug-drug interaction experiments were carried out between zolmitriptan and some drugs that may be co-administrated with zolmitriptan in the clinic. The results indicated that flunarizine, cetirizine, propranolol and atenolol potently decreased both the apical-to-basolateral and basolateral-to-apical transport rate of zolmitriptan. Cimetidine and aspirin slightly inhibited the apical-to-basolateral transport of zolmitriptan, but significantly decreased the basolateral-to-apical transport of zolmitriptan. Thus, the absorption drug-drug interactions should be considered when these drugs are co-administrated with zolmitriptan in the clinic.

'Party pill' drugs--BZP and TFMPP

BZP and TFMPP are amphetamine-like recreational drugs and the major active components of 'party pills'. The pharmacodynamic effects of these neurally active drugs are thought to be dependent on their activity at DA and 5-HT receptors and several studies report drug-drug interactions at a pharmacodynamic level. Their metabolism involves the hepatic P450 enzymes CYP2D6, CYP1A2 and CYP3A4 resulting in inhibited metabolism of other drugs and medicines, as well as compromised metabolism in poor metabolisers for CYP2D6. Basic pharmacokinetic properties are described for both BZP and TFMPP when taken alone and in combination. Several studies have shown that these drugs cause several drug-drug interactions.

In vivo interactions between BZP and TFMPP (party pill drugs)

AIM

This study explores potential drug-drug interactions between BZP and TFMPP. This was achieved by comparing the metabolism and pharmacokinetics of BZP and TFMPP when taken together with previously published data on their individual metabolism and pharmacokinetics.

METHOD

Blood and urine samples were collected from seven participants given a combined dose of BZP (100 mg) and TFMPP (30 mg) and analysed by LC-MS in order to quantify the concentrations of BZP, TFMPP, and their major hydroxylated metabolites 3-OH BZP, 4-OH BZP, and 4-OH TFMPP.

RESULTS

The metabolic profiles of both drugs were altered when co-administered. Both BZP and TFMPP lost one metabolite, 3-OH BZP and 4-OH TFMPP, respectively. Some differences in the pharmacokinetic properties of TFMPP were also noted.

CONCLUSION

Metabolic interactions between BZP and TFMPP are clearly observed in this study along with some changes to the pharmacokinetics of TFMPP. As these drugs are often co-administered, the interactions between them are both relevant and concerning. Awareness of these interactions can assist clinicians in understanding toxicities relating to the co-administration of BZP and TFMPP or other party pill drugs.

Disposition and metabolism of almotriptan in rats, dogs and monkeys

Almotriptan is a new highly potent selective 5-HT1B/1D receptor agonist developed for the treatment of migraine, and the disposition of almotriptan in different animal species is now addressed in the current study. Almotriptan was well absorbed in rats (69.1%) and dogs (100%) following oral treatment. The absolute bioavailability was variable reflecting different degrees of absorption and first-pass metabolism (18.7-79.6%). The elimination half-life was short and ranged between 0.7 and 3 h. The main route of elimination of almotriptan was urine with 75.6% and 80.4% of the dose recovered over a 168-h period in rats and dogs, respectively. The gamma-aminobutyric acid metabolite formed by oxidation of the pyrrolidine ring was the main metabolite found in urine, faeces, bile, and plasma of rats and in monkey urine. By contrast, the unchanged drug, the indole acetic acid metabolite formed by oxidative deamination of the dimethylaminoethyl group, and the N-oxide metabolite were the main metabolites in dog.

Intranasal mucoadhesive microemulsions of zolmitriptan: Preliminary studies on brain-targeting

The aim of this investigation was to prepare microemulsions containing zolmitriptan (ZT) for rapid drug delivery to the brain to treat acute attacks of migraine and to characterize microemulsions and evaluate biodistribution in rats. Zolmitriptan microemulsions (ZME) were prepared using the titration method and were characterized for globule size distribution and zeta potential. ZT was radiolabeled using (99m)Tc (technetium) and radiolabeled-drug formulations of ZT were used to carry out biodistribution of drug in the brain of Swiss albino rats after intranasal and intravenous administration. The pharmacokinetic parameters, drug targeting efficiency (%DTE) and direct nose-to-brain drug transport (%DTP) were calculated. Brain scintigraphy imaging in rats were also performed to ascertain the uptake of drug into the brain. ZME were transparent and stable with mean globule size of 35 +/- 25 nm and zeta potential of - 38- - 52 mV. (99m)Tc-labeled-drug formulations of ZT were found to be stable and suitable to perform in vivo studies. Following intranasal administrations of zolmitriptan mucoadhesive microemulsion (ZMME), ZME, Zolmitriptan solution (ZS) and intravenous administration of ZS, brain/blood uptake ratios at 0.50 h were found to be 0.70, 0.56, 0.27 and 0.13, respectively, indicating effective brain-targeting following intranasal administration of ZMME. Comparing intranasal administration of ZMME with intravenous administration of ZME, the %DTE and %DTP were found higher indicating effective drug transport following intranasal administration and highest brain-targeting following ZMME administration. Rat brain scintigrams showed substantial uptake of drug into the brain after intranasal administration of ZMME. Studies of this investigation conclusively demonstrated rapid and larger extent of transport into the rat brain following intranasal administration of ZMME and can play a promising role in the treatment of acute attacks of migraine.

Marketed oral triptans in the acute treatment of migraine: a systematic review on efficacy and tolerability

BACKGROUND

In the current literature, there is neither a reported systematic review comparing the efficacy of triptans at 30 minutes and 1 hour after the migraine treatment, nor data related to efficacy of new marketed triptans.

OBJECTIVE

The main objective of this analysis was to compare the efficacy and tolerability of currently marketed oral, non-reencapsulated triptan formulations vs placebo in the treatment of moderate-to-severe migraine attacks.

METHODS

A systematic review of double-blind, randomized clinical trials reporting data after a single migraine attack was conducted. Efficacy results are shown using relative risk ratios with 95% confidence intervals. A sensitivity analysis was also conducted.

RESULTS

After reviewing 221 publications, 38 studies were included. All marketed triptans provided significant relief and/or absence of pain at 2 hours, and relief at 1 hour when compared with placebo. After 30 minutes, fast-dissolving sumatriptan 50 and 100 mg, sumatriptan 50 mg, and rizatriptan 10 mg showed significant relief when compared to placebo, whereas the fast-dissolving formulation of sumatriptan 100 mg was the only oral triptan that was superior to placebo in meeting the pain-free endpoint. On the other hand, fast-dissolving sumatriptan 50 and 100 mg and eletriptan 40 mg showed a lower rate of recurrence than placebo, whereas rizatriptan 10 mg was the only triptan with a recurrence rate greater than that of placebo. Adverse events associated with treatment with tablet formulations of sumatriptan and zolmitriptan were significantly more frequent than those of the placebo group. The inclusion of trials with reencapsulated triptans in the analysis introduced minor specific changes in these results.

CONCLUSION

This analysis updates the comparative data available for the 7 currently marketed oral triptans and clearly demonstrates their efficacy when compared to placebo, even with stricter endpoints, such as efficacy at 30 minutes. No triptan exhibited better tolerability than placebo. Results are diverse, depending on the triptan, which probably is a reflection of heterogeneous pharmacokinetics.

Parenteral vs. oral sumatriptan and naratriptan: plasma levels and efficacy in migraine. a comment

The clinical efficacy in migraine was compared for oral and subcutaneous sumatriptan and naratriptan. Doses of the two administration forms were chosen as resulting in comparable blood concentrations. Subcutaneous administrations of the drugs were superior for efficacy than the oral forms. This most likely due to a quicker rise in blood concentrations after subcutaneous injections.. In designing new therapies for migraine one should aim at a quick absorption of the drug, which will probably result in an increased efficacy.

Sorbitan ester organogels for transdermal delivery of sumatriptan

The partial phase behavior, rheological, and drug release characteristics of an organogel (OG) composed of water, isooctane and sorbitan esters, sorbitan monopalmitate (Span-40) and poly(oxyethylene)sorbitan monostearate (Polysorbate-60) were studied. Phase diagrams showed decreasing areas of optically isotropic organogel region depending on the surfactant ratio, Kw and drug incorporation. The nonbirefringent, clear isotropic solution suggested the reverse micellar/microemulsion nature of the organogel without any molecular ordering. The increase in drug concentration in OGs leads to increase in the viscosity and sol-gel transition temperature (Tg). Fractal dimension (df) values calculated for different compositions suggested that the density of the tubular network increases with increasing drug concentration in OGs. The release rate of the drug from OGs was found to be non-Fickian through the dialysis membrane. The permeation rate of sumatriptan from pig skin was 0.231 mg/h/cm2 (781.9 nmol/h/cm2). The study indicates potential of OG as a reservoir system for transdermal drug delivery.

Pupillography as a sensitive, noninvasive biomarker in healthy volunteers: first-in-man study of BAY 63–9044, a new 5-HT1A-receptor agonist with dopamine agonistic properties

OBJECTIVE

BAY 63-9044 is a new full 5-HT(1A)-agonist with functional dopamine agonist properties aimed for the treatment of Parkinson's disease. This first-in-man study investigated the pharmacodynamics, safety and tolerability as well as the pharmacokinetics of BAY 63-9044 in a randomized, single-blind, placebo-controlled group-comparison dose escalation study.

METHODS

45 healthy men received BAY 63-9044 as an oral solution in single doses of 0.25 mg, 0.5 mg, 1.2 mg, 2.5 mg and 5.0 mg. Pupil reaction (baseline pupil diameter (DIAM), constriction amplitude (CA)), body temperature, electroencephalography (EEG) and prolactin, cortisol and adrenocorticotrophic hormone (ACTH) served as pharmacodynamic measures and were monitored up to 24 h after drug intake. Safety, tolerability and plasma samples for determination of BAY 63-9044 were followed up to 72 h.

RESULTS

Up to a dose of 2.5 mg, BAY 63-9044 was safe and well tolerated. Dose-limiting adverse events (nausea, vomiting, and dizziness) occurred in 5 out of 6 volunteers at the 5 mg dose. Adverse events resolved spontaneously in all but one volunteers who was treated with an antihistaminergic for vomiting. Dose-dependent changes of DIAM and CA were observed at doses higher than 0.5 mg and 1.2 mg, respectively. Body temperature showed a trend for reduction starting at C(max) in the highest two doses only. No clear effect was found on prolactin, cortisol and ACTH levels. The pharmacokinetics of BAY 63-9044 showed a dose-dependent increase with maximum plasma concentrations reached within 1 h. Plasma concentrations declined in a bi-phased manner with an apparent terminal half-life of 5.2-8.1 h.

CONCLUSION

Up to the maximum tolerated dose (MTD) of 2.5 mg BAY 63-9044 was safe and well tolerated and showed predictable linear pharmacokinetics. Pupil reaction may serve as a non-invasive biomarker for pharmacodynamic effects of 5-HT(1A)-compounds with DIAM being the most sensitive parameter.

An evaporation-free solid-phase extraction method for rapid and accurate analysis of sumatriptan in human plasma by LC–MS/MS

An evaporation-free solid-phase extraction (SPE) method was developed and validated for sumatriptan. High organic washing (50% methanol) and low organic elution (20% methanol) were used and the recovery was greater than 92%. The eluate was injected into a C18 column without evaporation and reconstitution. Sumatriptan was monitored in positive ion mode with mass transition of m/z 296.4-58.1 amu. The calibration curve was 1-100 ng/mL (r>or=0.9923). The inter-day and intra-day precisions ranged from 4.53 to 9.12% and 1.72 to 6.93%, respectively. This method features reduced cost and pollution, clean extract, high speed, and most importantly overall method reliability.

[Determination of mosapride in human plasma by high performance liquid chromatography tandem mass spectrometry]

To develop a sensitive and specific high performance liquid chromatography-tandem mass spectrometric (HPLC-MS/MS) method for the determination of mosapride in human plasma, mosapride and internal standard tamsulosin were extracted from plasma with liquid-liquid extraction, then separated on a Waters ACQUITY UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm ID) with gradient elution at flow-rate of 0.25 mL x min(-1). The mobile phase was water (containing 0.3% formic acid) and acetonitrile under gradient conditions. Electrospray ionization (ESI) source was applied and operated in the positive ion mode. Multiple reaction monitoring (MRM) mode with the transitions of m/z 422 --> m/z 198 and m/z 409 --> m/z 228 were used to quantify mosapride and the internal standard, respectively. The linear calibration curve was obtained in the concentration range of 0.17 - 68.00 ng x mL(-1). The lower limit of quantification was 0.17 ng x mL(-1). The inter- and intra-day precision (RSD) was less than 13%, and the accuracy (RE) was within +/- 6.3% calculated from QC samples. The method was used to determine the concentration of mosapride in plasma after a single oral dose of 5 mg mosapride citrate to 20 healthy male Chinese volunteers. The method has been proved to be selective, sensitive, rapid and suitable for pharmacokinetic study of mosapride.

A Unique Iontophoretic Patch for Optimal Transdermal Delivery of Sumatriptan

PURPOSE

Migraines affect approximately 10% of the adult population worldwide. The purpose of this study was to assess the pharmacokinetic and safety profile of a novel iontophoretic sumatriptan delivery system, NP101, which uses an electrical current to propel sumatriptan across intact skin and into underlying tissue. Four unique prototype iontophoretic sumatriptan patch conditions were compared to a 6 mg subcutaneous injection and an oral 50 mg tablet of sumatriptan succinate.

MATERIALS AND METHODS

This was a randomized, single-center, single-dose, six-period Phase I study.

RESULTS

Patches were well tolerated with fewer adverse events than the subcutaneous injection. Adverse events that were more prevalent for NP101 than other formulations included localized sensations and reactions at the patch site. A linear relationship was observed between total applied current and sumatriptan delivery. Patches delivering 6 and 12 mA per h yielded favorable sumatriptan systemic profiles, delivering drug at a rate that maintained plasma levels above the target level (> or = 10 ng/ml) for greater than 7 h.

CONCLUSIONS

This study met the initial objective to define the dose-current relationship in humans as well as delimiting specific current and current density targets for a well tolerated patch design that can deliver therapeutic drug levels for longer periods than currently possible.

Uptake and biodistribution of rizatriptan to blood and brain following different routes of administration in rats

The objective of the present study was to investigate the biodistribution profiles of rizatriptan in the blood and brain of Wistar rats after peroral, subcutaneous, intranasal and intratracheal administration with a particular view to determining the applicability of inhalation delivery to achieve rapid and high availability of the drug in both blood and the brain. Following the intratracheal administration of the drug (4.0mg/kg) to the rats, the absolute bioavailability was found to be 91.2%, significantly higher than those from intranasal or peroral routes, and T(max) in plasma and brain was attained within 2 min, significantly shorter than the T(max) of intranasal ( approximately 10 min in both plasma and brain), subcutaneous (16.7 min in plasma and 22.5 min in brain) and peroral (30.0 min in plasma and 45.0 min in brain) administration. In addition, other pharmacokinetic parameters associated with rapid onset of action including AUC(plasma/brain) and C(max), of intratracheal instillated rizatriptan appeared also to be comparable or superior to those of other delivered routes. Although AUC(brain)/AUC(plasma) ratios after intranasal delivery (43.4%) differed significantly from the ratios shown after intratracheal instillation (23.2%), the AUC(brain 0-120 min) via the latter routes was slightly but not significantly higher than that from the former routes. The results in the present study indicated that pulmonary delivery of rizatriptan may achieve maximum plasma and brain concentrations significantly more rapidly compared with intranasal, subcutaneous and peroral administration and be a promising delivery method with extremely rapid onset of action in the pain relief of migraine.

6-Hydroxybuspirone Is a Major Active Metabolite of Buspirone: Assessment of Pharmacokinetics and 5-Hydroxytryptamine1AReceptor Occupancy in Rats

The pharmacokinetics and in vivo potency of 6-hydroxybuspirone (6-OH-buspirone), a major metabolite of buspirone, were investigated. The plasma clearance (47.3 +/- 3.5 ml/min/kg), volume of distribution (2.6 +/- 0.3 l/kg), and half-life (1.2 +/- 0.2 h) of 6-OH-buspirone in rats were similar to those for buspirone. Bioavailability was higher for 6-OH-buspirone (19%) compared with that for buspirone (1.4%). After intravenous infusions to steady-state levels in plasma, 6-OH-buspirone and buspirone increased 5-hydroxytryptamine (HT)(1A) receptor occupancy in a concentration-dependent manner with EC(50) values of 1.0 +/- 0.3 and 0.38 +/- 0.06 microM in the dorsal raphe and 4.0 +/- 0.6 and 1.5 +/- 0.3 microM in the hippocampus, respectively. Both compounds appeared to be approximately 4-fold more potent in occupying presynaptic 5-HT(1A) receptors in the dorsal raphe than the postsynaptic receptors in the hippocampus. Oral dosing of buspirone in rats resulted in exposures (area under the concentration-time profile) of 6-OH-buspirone and 1-(2-pyrimidinyl)-piperazine (1-PP), another major metabolite of buspirone, that were approximately 12 (6-OH-buspirone)- and 49 (1-PP)-fold higher than the exposure of the parent compound. As a whole, these preclinical data suggest that 6-OH-buspirone probably contributes to the clinical efficacy of buspirone as an anxiolytic agent.

In vitro and in vivo evaluation of the transdermal iontophoretic delivery of sumatriptan succinate

The objective was to evaluate the transdermal delivery of the 5-HT(1B/1D) agonist, sumatriptan from an iontophoretic patch system, in vivo. Initial in vitro experiments were conducted to optimize formulation parameters prior to iontophoretic delivery in Yorkshire swine. It was found in vitro that increasing drug load in the patch from 9.7 to 39 mg had no statistically significant effect on cumulative delivery (cf. 305.6+/-172.4 vs. 389.4+/-80.4 microg cm(-2), respectively). However, for a given drug load (39 mg) increasing formulation pH from pH 4.7 to 6.8 significantly increased the cumulative amount of sumatriptan delivered across the skin (389.4+/-80.4 vs. 652.4+/-94.2 microg cm(-2)). A biphasic current profile comprising intensities of 1.8 mA from t=0 to t=180 min and 0.8 mA from t=181 min to t=360 min was used for the in vivo experiments. Drug levels in the blood were 13.7+/-4.5 and 53.6+/-10.2 ng ml(-1) at the 30 and 60 min time-points, rising to 90-100 ng ml(-1) during the 90-180 min time-period. The in vivo results show that the pharmacokinetics following transdermal iontophoretic delivery are comparable to those after oral, nasal or rectal administration, but do not match those upon subcutaneous injection.

Pharmacokinetics of sarizotan after oral administration of single and repeat doses in healthy subjects

OBJECTIVE

Sarizotan is a 5-HTIA receptor agonist with high affinity for D3 and D4 receptors. Here we report the pharmacokinetic and tolerability results from four Phase 1 studies.

MATERIALS

Two single-dose (5 -25 mg, n = 25, 0.5 - 5 mg, n = 16) and two multiple-dose (10 and 20 mg b.i.d., n = 30, 5 mg b.i.d., n = 12) studies with orally administered sarizotan HCl were carried out in healthy subjects.

METHODS

Plasma sarizotan HCl concentrations were measured using a validated HPLC method and fluorescence or MS/MS detection. Pharmacokinetic parameters were obtained using standard non-compartmental methods.

RESULTS

Sarizotan was rapidly absorbed, group-median times to reach maximum concentration (tmax) ranged from 0.5 -2.25 h after single doses and during steady state. Maximum plasma concentration (Cmax) and tmax were slightly dependent on formulation and food intake, whereas area under the curve (AUC) was unaffected by these factors. AUC and Cmax increased dose-proportionally over the tested dose range. Independently of dose and time, sarizotan HCl plasma concentrations declined polyexponentially with a terminal elimination half-life (t1/2) of 5 - 7 h. Accumulation factors corresponded to t1/2 values, and steady state was reached within 24 h. Plasma metabolite concentrations were considerably lower than those of the parent drug. The ratio metabolite AUC : parent drug AUC was time- and dose-independent for all three metabolites suggesting that the metabolism of sarizotan is non-saturable in the tested dose range.

CONCLUSIONS

The pharmacokinetics of sarizotan were dose-proportional and time-independent for the dose range 0.5 -25 mg). The drug was well-tolerated by healthy subjects up to a single dose of 20 mg.

Tegaserod for constipation-predominant irritable bowel syndrome

Tegaserod, a selective and partial agonist at the 5-hydroxytryptamine (5-HT [serotonin]) receptor subtype 4 (5-HT4), is the only United States Food and Drug Administration-approved drug for the treatment of constipation-predominant irritable bowel syndrome (IBS) in women. The drug's stimulation of 5-HT4 receptors on intestinal enterocytes increases peristaltic activity and fluid secretion into the gut lumen, facilitating stool passage. In addition, affinity of tegaserod for 5-HT4 receptors modulates visceral sensitivity, which helps alleviate abdominal pain associated with constipation-predominant IBS. The drug's pharmacokinetic and pharmacodynamic parameters do not differ significantly with age or sex. Tegaserod safely and effectively relieves overall gastrointestinal symptoms and abdominal discomfort and normalizes bowel habits in patients with constipation-predominant IBS. It is associated with few drug interactions. In clinical studies, tegaserod was well tolerated, and its adverse-effect profile was similar to that of placebo. Severe diarrhea, as well as abdominal pain, flatulence, headache, and nausea, were the most commonly reported events. Patients who experience severe diarrhea should discontinue the drug. With the data available, tegaserod remains an option for patients with constipation-predominant IBS.

A model-based approach to treatment comparison in acute migraine

AIMS

Currently, direct comparisons between 5-HT(1B/d) receptor agonists are used to assess differences and similarities in antimigraine response. Such comparisons depend on the selected sampling time and do not allow evaluation of entire response profiles. A thorough evaluation of drug properties requires that the time course of the response be taken into account. In this investigation we show the advantages of a model-based approach to compare the efficacy of two triptans (sumatriptan vs. naratriptan).

METHODS

A Markov model was used to describe the course of a migraine attack over three clinically identified stages. Drug effects were modelled as concentration-dependent increases in transition rates and were parameterised as potency (EC(50)) and maximum effect (E(max)). Parameters were estimated using headache measurements from efficacy studies. Model estimates were then used to compare the pharmacodynamics of the two drugs in a time-independent manner.

RESULTS

Efficacy parameters could be derived, allowing for comparison between compounds. The potency ratio (EC50(suma)/EC50(nara)) for headache relief was 3.3 (0.9, 12). The ratio of maximum effects (Emax(suma)/Emax(nara)) for this endpoint was 0.74 (0.55, 0.97). To interpret these efficacy measures and explore their value for the development of antimigraine drugs, results were evaluated against the reported in vitro potency at 5-HT(1B) and 5-HT(1D) receptors.

CONCLUSIONS

Comparison of the effects of two or more drugs based on preset sampling times does not allow proper assessment of the antimigraine properties in vivo. Disease dynamics must be considered to evaluate treatment response adequately and optimise the dosing regimen in migraine.

Pharmacokinetics and interactions of headache medications, part I: introduction, pharmacokinetics, metabolism and acute treatments

Recent progress in the treatment of primary headaches has made available specific, effective and safe medications for these disorders, which are widely spread among the general population. One of the negative consequences of this undoubtedly positive progress is the risk of drug-drug interactions. This review is the first in a two-part series on pharmacokinetic drug-drug interactions of headache medications. Part I addresses acute treatments. Part II focuses on prophylactic treatments. The overall aim of this series is to increase the awareness of physicians, either primary care providers or specialists, regarding this topic. Pharmacokinetic drug-drug interactions of major severity involving acute medications are a minority among those reported in literature. The main drug combinations to avoid are: i) NSAIDs plus drugs with a narrow therapeutic range (i.e., digoxin, methotrexate, etc.); ii) sumatriptan, rizatriptan or zolmitriptan plus monoamine oxidase inhibitors; iii) substrates and inhibitors of CYP2D6 (i.e., chlorpromazine, metoclopramide, etc.) and -3A4 (i.e., ergot derivatives, eletriptan, etc.), as well as other substrates or inhibitors of the same CYP isoenzymes. The risk of having clinically significant pharmacokinetic drug-drug interactions seems to be limited in patients with low frequency headaches, but could be higher in chronic headache sufferers with medication overuse.

Serotonin-caused phase shift of circadian rhythmicity in a photosensitive neuron

In the sixth abdominal ganglion (sixth AG) of the crayfish, two photosensitive neurons are located and have been identified as caudal photoreceptors (CPRs). We have expanded our investigation on the role of 5-Hydroxytryptamine (5-HT) as a modulator of the spontaneous and light-induced activity of the CPR. We located, by using immunocytochemistry, neurons in the sixth AG that contain the 5HT1A receptor. The expression of these receptors was examined by binding assays with [3H] 8-hydroxy-2 (di-n-propylamino) tetralin ([3H(8-OH-DPAT). We examined the exogenous action of both 5HT and its agonist 8-OH-DPAT on the phase of circadian rhythms of the spontaneous electrical activity and the photoresponse of the CPR in the isolated sixth AG by conventional extracellular recording methods. Experiments were made on the adult crayfish Procambarus clarkii and Cherax quadricarinatus. Thirteen immunopositive neurons were located, principally near the ventral and dorsal surface of the sixth AG, with the mean diameter of their somata 20+/-3 microm. The specific binding data showed the presence of 5-HT1A receptors with a mean level of 22.4+/-6.6 fmol/mg of wet tissue. Spontaneous and light-induced electrical activity of the CPR showed circadian variations with their activity more intense at night than in the day. Exogenous application of 5-HT or 8-OH-DPAT causes a circadian phase-shift in electrical activity of the CPR. Taken together, these results lead us to believe the 5-HT acts as a modulator of circadian electrical activity of the CPR in the isolated sixth AG of crayfish. Moreover, it suggests that the 5-HT1A receptor participates in this modulation.

Pharmacokinetics and in vitro effects of tegaserod, a serotonin 5-hydroxytryptamine 4 (5-HT4) receptor agonist with prokinetic activity in horses

Tegaserod, a serotonin agonist, has been shown to have prokinetic effects in horses, but pharmacokinetic information is not currently available. The pharmacokinetics and in vitro effects of tegaserod were evaluated. Tegaserod increased the contractile activity of smooth muscle preparations of the equine pelvic flexure. Pertinent pharmacokinetic parameters for a single IV and oral dose were determined. Therapeutic plasma concentrations of tegaserod were achieved by a single oral dose at 0.27 mg/kg. These findings indicate that further clinical studies are warranted to investigate potential benefits in cases of functional gastrointestinal motility disorders in horses.

Pharmacokinetics of buspirone in autistic children

Buspirone is used to treat generalized anxiety disorder in children and may be useful in developmental disorders in which brain serotonin synthesis is altered. Autistic children (13 boys, 7 girls) were given a single oral dose of 2.5 mg (2-3 years) or 5.0 mg (4-6 years). Blood was collected for 8 hours, and plasma was assayed for buspirone and its metabolite 1-pyrimidinylpiperazine (1-PP). The peak concentration of buspirone averaged 1141 +/- 748 pg/mL with a time to maximum concentration of 0.8 hours. Half-life was 1.6 +/- 0.3 hours. Peak concentrations of 1-PP were 4.5-fold higher than for buspirone. Girls had higher peak concentrations (1876 vs 746 pg/mL) for buspirone and a lower peak 1-PP/buspirone concentration ratio. These results suggest that buspirone is rapidly absorbed and eliminated in young children with extensive metabolism to 1-PP. Plasma concentrations with 2.5- to 5.0-mg doses were similar to those observed in older children receiving 7.5- to 15-mg doses.

Cocaine-mediated supersensitivity of 5-HT2A receptors in hypothalamic paraventricular nucleus is a withdrawal-induced phenomenon

We previously reported that treatment and withdrawal from cocaine increases: (1) 5-HT2A receptor-mediated neuroendocrine responses, and (2) Galphaq and Galpha11 G-protein levels in the hypothalamic paraventricular nucleus (PVN) at 48 h post-treatment. This study investigates changes in the initial 24 h of withdrawal to discern whether 5-HT2A receptor supersensitivity is due to cocaine treatment or is induced during the withdrawal period. We report here increases in 5-HT2A receptor-mediated neuroendocrine responses only 12 or 24 h post-treatment, but not during the initial 4 h withdrawal period. Levels of membrane- or cytosol-associated Galphaq or Galpha11 proteins in PVN are not altered during the first 24 h of withdrawal. However, the density of 125I-(-)-1-(2,5 dimethoxy-4-iodophenyl)-2-amino-propane HCl (DOI)-labeled high-affinity 5-HT2A receptors in PVN increased 35% in rats withdrawn from cocaine for 24 h. These findings demonstrate that cocaine-induced increases in 5-HT2A receptor function in PVN represents a withdrawal-induced phenomena that: (1) is likely attributed to increased G-protein coupled/high-affinity conformational state of the 5-HT2A receptor, and (2) occurs in the absence of changes in the levels of associated G proteins during the first 24 h.

Combination strategies for enhancing transdermal absorption of sumatriptan through skin

The aim of the present work was to characterize in vitro sumatriptan transdermal absorption through human skin and to investigate the effect of chemical enhancers and iontophoresis applied both individually and in combination. A secondary objective was to compare the results obtained with those in porcine skin under the same conditions, in order to characterize the relationship between the two skin models and validate the porcine model for further research use. Transdermal flux of sumatriptan was determined in different situations: (a) after pre-treatment of human skin with ethanol, Azone (1-dodecyl-azacycloheptan-2-one), polyethylene glycol 600 and R-(+)-limonene, (b) under iontophoresis application (0.25 and 0.50 mA/cm(2)) and (c) combining chemical pre-treatment and iontophoresis at 0.50 mA/cm(2) current density. All the strategies applied enhance sumatriptan transdermal absorption. A linear relationship between the fluxes in the two skin models in the different conditions assayed can be established. The combination of both strategies, Azone and iontophoresis, proved to be the most effective of the techniques for enhancing the transdermal absorption of sumatriptan. The flux obtained with porcine skin in vitro is approximately double that obtained in human skin.

Alterations in 5-HT2A receptor signaling in male and female transgenic rats over-expressing either Gq or RGS-insensitive Gq protein

Serotonin 2A (5-HT2A) receptors are coupled to Galphaq and Galpha11 proteins to activate phospholipase C (PLC). Regulators of G-protein signaling proteins (RGS) modulate G-protein signaling by accelerating the intrinsic GTPase activity of Galphaq and Galpha11. This study investigated the effects of over-expression of wild-type Galphaq proteins (Gq-Tg) and over-expression of RGS-insensitive Galphaq proteins (G188S, RGSi-Tg) on 5-HT2A receptor mediated signaling in transgenic rats. Over-expression of wild-type Galphaq and RGS insensitive mutant Galphaq did not produce significant alterations in the levels of Galpha11, RGS2, RGS4, RGS7, RGS16 or 5-HT2A proteins. RGSi-Tg rats had higher oxytocin and corticosterone responses to (-)DOI, a 5-HT2A/2C receptor agonist, compared to Gq-Tg rats. RGSi-Tg and Gq-Tg rats had higher ACTH responses to (-)DOI compared to control rats. Similarly, 5-HT-stimulated PLC activity in the frontal cortex was higher in RGSi-Tg and Gq-Tg rats compared to control rats. In contrast, GTPgammaS-stimulated PLC activity was higher in Gq-Tg rats but not in RGSi-Tg rats compared to control rats. There was a small but statistically significant increase in the affinity of [125I]-DOI labeled 5-HT2A receptors in RGSi-Tg rats and Gq-Tg rats compared to controls. There were no significant differences in Bmax and Kd of [3H] ketanserin labeled 5-HT2A receptors among the three groups. These data suggest that the effect of RGS proteins on 5-HT2A receptor signaling is cell type specific. In transgenic rats over-expressing Galphaq, endogenous RGS proteins have a negative effect on 5-HT2A receptor-mediated oxytocin release. In contrast, endogenous RGS protein had no impact on 5-HT2A receptor-mediated ACTH release in transgenic rats.

Ethanol does not significantly affect the bioavailability of almotriptan: an open, randomized, crossover, single-dose, phase I clinical trial in healthy volunteers

OBJECTIVE

A number of clinical reports have revealed a link between the use of alcohol and the onset or exacerbation of migraine headaches. This open, randomized, crossover, single-dose, phase I clinical trial evaluated the possible pharmacokinetic interactions between a single oral dose of almotriptan 12.5 mg, a 5-HT(1B/1D receptor agonist for the acute treatment of migraine, and ethanol in 16 healthy male volunteers. Tolerability and safety of this combined treatment were also assessed.

METHODS

Subjects received a crossed oral dose of almotriptan (12.5 mg) with and without concomitant alcohol intake (target plasma concentration 0.8 g/kg) in two different treatment periods. Almotriptan was administered alone, while ethanol was diluted with orange juice, which was also given to the control group. There was a washout period of 7 days between treatments. Plasma levels of almotriptan were analyzed using a sensitive and specific liquid chromatographic-tandem mass spectrometry method.

RESULTS

The 90% non-parametric confidence interval for the median t(max) of almotriptan plus ethanol compared to almotriptan alone (0.61/2.72) was outside the acceptable range (0.70 - 1.30), demonstrating that concomitant ethanol administration slightly increases the variability of absorption of almotriptan 12.5 mg. In contrast, the main bioavailability criteria parameters, C(max) and AUC, which show the rate and extent of systemic absorption, were not affected by alcohol ingestion. Therefore, it is unlikely that concomitant ethanol intake would produce clinically relevant differences in the therapeutic effect of almotriptan at the dose studied here. Tolerability of treatments was good throughout the entire study period.

CONCLUSIONS

Almotriptan 12.5 mg, with or without concomitant alcohol ingestion, showed similar plasma concentrations after a single dose in healthy volunteers with no clinically relevant drug-to-drug interactions.

WAY-100635 antagonist-induced plasticity of 5-HT receptors: regulatory differences between a stable cell line and an in vivo native system

We present evidence that the 5-hydroxytryptamine(1A) (5-HT(1A)) receptor antagonist, N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl}-N-(2-pyridinyl)cyclohexanecarboxamide (WAY-100635), can induce receptor internalization in a human (h)5-HT(1A) receptor Chinese hamster ovary (CHO-K1) cell system. Exposure of h5-HT(1A) CHO cells to WAY-100635 decreased the cell-surface h5-HT(1A) receptor density in a way that was both time (24-72 h) and concentration (1-100 nm) dependent.[(3)H]WAY-100635 and [(3)H]8-hydroxy-dipropylaminotetralin ([(3)H]8-OH-DPAT) saturation analyses demonstrated a significant reduction (50-60%) in total h5-HT(1A) receptor number in the WAY-100635-treated (100 nm; 72 h) compared with control cells. In WAY-100635-treated cells, the 8-OH-DPAT-mediated inhibition of forskolin (FSK)-stimulated cAMP accumulation was right-shifted and the maximal inhibitory response of 8-OH-DPAT was impaired compared with control cells. Similar results were obtained for 8-OH-DPAT-mediated Ca(2+) mobilization after WAY-100635 treatment. h5-HT(1A) receptors labeled with [(3)H]WAY-100635, as well as [(3)H]4-(2'-Methoxy)-phenyl-1-[2'-(N-2''-pyridinyl)-p-fluorobenzamido]ethyl-piperazine (MPPF), exhibited a time-dependent rate of cellular internalization that was blocked by endocytotic suppressors and was pertussis-toxin insensitive. In contrast, quantitative autoradiographic studies demonstrated that chronic treatment of rats with WAY-100635 for two weeks produced a region-specific increase in the 5-HT(1A) receptor density. In conclusion, prolonged exposure of an h5-HT(1A) cell-based system to the 5-HT(1A) antagonist, WAY-100635, induced a paradoxical internalization of cell surface receptor resulting in depressed functional activity. This suggests that an antagonist can influence 5-HT(1A) receptor recycling in vitro differently to in vivo regulatory conditions.

The design and synthesis of a tricyclic single-nitrogen scaffold that serves as a 5-HT2C receptor agonist

5-HT2C agonists have shown efficacy in limiting food consumption and thus may serve as an important drug class in combating obesity. We describe the design and synthesis of a novel tricyclic single-nitrogen scaffold that was used to produce 5-HT2C agonists. SAR was developed around this chemotype and compounds were identified that were potent (Ki<15 nM) and selective relative to other 5-HT2 receptors. The most promising compound displayed a good pharmacokinetic profile in multiple animal species, and was efficacious in an acute feeding study in rats.

Which triptan for which patient?

The triptans were developed for the acute treatment of a migraine attack and have revolutionised the treatment of this disorder since their introduction in the early 1990s. Although their mechanisms of actions are similar and based on the stimulation of specific serotonin (5-hydroxytryptamine) receptors including peripheral 1B and central and peripheral 1D subtypes, each triptan has its own distinctive pK properties that result in different profiles of efficacy and tolerability. Triptans work by decreasing neurogenic inflammation peripherally in the meninges, vasoconstriction of meningeal vessels and by modulating secondary-order neurons in the brain stem. Studies of patient attitudes towards their acute care regimens reveal that they are often unhappy with some aspect of their treatment-usually the speed of action, degree of efficacy, presence of adverse events and the need for additional doses due to frequent and/or rapid recurrence. The majority of patients, when asked in a clinical trial performed at tertiary care headache centres, are willing to try another triptan. The aim of this article is to review the pK and clinical characteristics of these acute care, migraine-specific triptan medications and discuss how their individual characteristics lead to their preferred choice in various clinical scenarios. The pK and clinical efficacy data presented are taken from older published studies in which triptans were compared to placebo or each other, but the patients were asked to wait till the headache reached moderate or severe intensity prior to taking study medication. New studies have looked at early treatment paradigms and result in better efficacy data, but are difficult to compare due to different endpoints.

Diurnal rhythm in the levels of the serotonin 5-HT1A receptors in the crayfish eyestalk

The crayfish eyestalk (ES) has been postulated as a possible circadian clock. 5-Hydroxytryptamine (5-HT) has been shown to play the role of a neurotransmitter or a modulator in the ES. However, little is known about the 5-HT receptors in the ES. The purpose of this work is to determine the specific binding sites using [(3)H]8-hydroxy-2(di-n-propylamino)tetralin ([(3)H]8-OH-DPAT), a specific agonist of the 5-HT(1A) receptor, and to characterize the diurnal rhythm in the binding by an autoradiography procedure in the crayfish ES. Data show the presence of a circadian rhythmicity in the level of the 5-HT(1A) receptors, principally in two regions: (a) the complex retina (R)-lamina ganglionaris (LG), with the acrophase at dusk and (b) the medulla terminalis (MT), where it was in antiphase. It is suggested that (1) the expression of levels of 5-HT(1A) receptors is modulated by light-dark (LD) cycles, (2) the level of 5-HT(1A) receptors in the R-LG and MT are in antiphase during the 24-h cycle, and (3) there is a different mechanism of action of LD cycles in each of these two anatomical regions of the crayfish ES.

Blood-brain barrier penetration of zolmitriptan--modelling of positron emission tomography data

Positron emission tomography (PET) with the drug radiolabelled allows a direct measurement of brain or other organ kinetics, information which can be essential in drug development. Usually, however, a PET-tracer is administered intravenously (i.v.), whereas the therapeutic drug is mostly given orally or by a different route to the PET-tracer. In such cases, a recalculation is needed to make the PET data representative for the alternative administration route. To investigate the blood-brain barrier penetration of a drug (zolmitriptan) using dynamic PET and by PK modelling quantify the brain concentration of the drug after the nasal administration of a therapeutic dose. [11C]Zolmitriptan at tracer dose was administered as a short i.v. infusion and the brain tissue and venous blood kinetics of [11C]zolmitriptan was measured by PET in 7 healthy volunteers. One PET study was performed before and one 30 min after the administration of 5 mg zolmitriptan as nasal spray. At each of the instances, the brain radioactivity concentration after subtraction of the vascular component was determined up to 90 min after administration and compared to venous plasma radioactivity concentration after correction for radiolabelled metabolites. Convolution methods were used to describe the relationship between arterial and venous tracer concentrations, respectively between brain and arterial tracer concentration. Finally, the impulse response functions derived from the PET studies were applied on plasma PK data to estimate the brain zolmitriptan concentration after a nasal administration of a therapeutic dose. The studies shows that the PET data on brain kinetics could well be described as the convolution of venous tracer kinetics with an impulse response including terms for arterial-to-venous plasma and arterial-to-brain impulse responses. Application of the PET derived impulse responses on the plasma PK from nasal administration demonstrated that brain PK of zolmitriptan increased with time, achieving about 0.5 mg/ml at 30 min and close to a maximum of 1.5 mg/ml after 2 hr. A significant brain concentration was observed already after 5 min. The data support the notation of a rapid brain availability of zolmitriptan after nasal administration.

Effect of food intake on the bioavailability of almotriptan, an antimigraine compound, in healthy volunteers: an open, randomized, crossover, single-dose clinical trial

This open, randomized, crossover, single-dose clinical trial evaluated the possible pharmacokinetic interaction between a single oral dose of almotriptan 25 mg, a 5-HT1B/1D receptor agonist for the acute treatment of migraine, and food intake in healthy volunteers. The influence of food intake in the rate and extent of almotriptan absorption was evaluated by bioequivalence criteria. Tolerability and safety of treatment were also assessed. 16 healthy volunteers (8 men and 8 women, aged 19-27 years) received a crossed single oral dose of almotriptan 25 mg under fasting and fed conditions, separated by a 7-day washout period. The treatment given under fasting condition was considered as reference. Plasma levels of almotriptan were analyzed using high-performance liquid chromatography (HPLC) and UV detection at 227 nm. The 90% confidence intervals (CI) for the logarithmically transformed Cmax and AUC0-infinity, values of almotriptan under fasting and fed conditions (97.8 - 124% and 102.9 - 108.2%, respectively) fell into the predetermined accepted range of 80 - 125%. No statistically significant differences in Cmax, tmax, AUC0-infinity, MRT and t1/2 were observed under fasting and fed conditions between men and women. Tolerability of treatments was good throughout the whole study period. In conclusion, administration of almotriptan 25 mg is bioequivalent under fasting and fed conditions in healthy men and women. Therefore, it is unlikely that concomitant food intake would produce clinially relevant differences in therapeutic effect with almotriptan at the dose studied here.

Preclinical neuropharmacology of naratriptan

The basic CNS neuropharmacology of naratriptan is reviewed here. Naratriptan is a second-generation triptan antimigraine drug, developed at a time when CNS activity was thought not to be relevant to its therapeutic effect in migraine. It was, however, developed to be a more lipid-soluble, more readily absorbed and less readily metabolized variant on preexisting triptans and these variations conferred on it a higher CNS profile. Naratriptan is a 5-HT(1B/1D) receptor agonist with a highly selective action on migraine pain and nausea, without significant effect on other pain or even other trigeminal pain. Probable sites of therapeutic action of naratriptan include any or all of: the cranial vasculature; the peripheral terminations of trigeminovascular sensory nerves; the first-order synapses of the trigeminovascular sensory system; the descending pain control system; and the nuclei of the thalamus. Naratriptan may prevent painful dilatation of intracranial vessels or reverse such painful dilatation. Naratriptan can prevent the release of sensory peptides and inhibit painful neurogenic vasodilatation of intracranial blood vessels. At the first order synapse of the trigeminal sensory system, naratriptan can selectively suppress neurotransmission from sensory fibers from dural and vascular tissue, while sparing transmission from other trigeminal fibers, probably through inhibition of neuropeptide transmitter release. In the periaqueductal gray matter and in the nucleus raphe magnus, naratriptan selectively activates inhibitory neurons which project to the trigeminal nucleus and spinal cord and which exert inhibitory influences on trigeminovascular sensory input. Naratriptan has also a therapeutic effect on the nausea of migraine, possibly exerting its action at the level of the nucleus tractus solitarius via the same mechanisms by which it inhibits trigeminovascular nociceptive input. The incidence of naratriptan-induced adverse effects in the CNS is low and it is not an analgesic for pain other than that of vascular headache. In patients receiving selective serotonin uptake inhibitors (SSRIs) naratriptan may cause serotonin syndrome-like behavioral side effects. The mechanism of action involved in the production of behavioral and other CNS side effects of naratriptan is unknown.