Antinociceptive effects of serotonergic reuptake inhibitors in mice

The antinociceptive effects of three predominantly serotonergic reuptake inhibitors, alaproclate, citalopram and clomipramine, were examined in mice using the hot-plate, formalin and substance P tests. The effects were compared with those of the noradrenergic reuptake inhibitor, desipramine. Different profiles in the three nociceptive tests were found for all four drugs, using doses of 10 and 40 mg/kg. The selective serotonergic reuptake inhibitor, alaproclate, seemed to have the least antinociceptive effects, and was the only drug that was ineffective in the hot-plate test. The other selective drug, citalopram, had a stronger effect than alaproclate in the substance P test, but in the formalin test, both drugs were approximately equally effective. Clomipramine differed from citalopram by being more effective in the formalin test. These findings thus indicate that selective inhibitors of the uptake of 5-HT have weaker antinociceptive effects than less selective drugs. Desipramine seemed to be no less effective than the serotonergic drugs and was the most potent drug in the hot-plate test.     

Potent and long-lasting potentiation of two 5-hydroxytryptophan- induced effects in mice by three selective 5-ht uptake inhibitors.

The effect of i.p. administered 5-hydroxytrptophan (5-HTP) on electroschock seizures and motility was studied in mice. High doses (600–2000 mg/kg) produced an anticonvulsant effect and hypermotility. Both effects were inhibited by the central decarboxylase inhibitor NSD 1015 (100 mg/kg i.p.) and potentiated by the peripheral decarboxylase inhibitor Ro 4-4602 (5 mg/kg i.p.). The catecholamine sysnthesis inhibitor α-methyl-p-tyrosine or H $\text{44}\text{68}$ (100 and 200 mg/kg i.p.) did not alter the anticonvulsant effect but H $\text{44}\text{68}$ (200 mg/kg i.p.). inhibited the hypermotility. Six inhibitors of neuronal NA and 5-HT uptake were administered orally at various times before 5-HTP (150 mg/kg), which alone was devoid of anticonvulsant effect and produced a weak hypermotility. Low doses of the selective 5-HT-uptake inhibitors paroxetine, fluoxetine and zimelidine potentiated both 5-HTP-induced effects. The selective NA uptake inhibitor protriptyline showed no or weak 5-HTP potentiation. These results indicate that the anticonvulsant effect of 5-HTP is dependent on increased synthesis and release of brain 5-HT. Both 5-HT and catecholamine release are presumably involved in mediating 5-HTP-induced hypermotility since selective 5-HT uptake inhibitors were the strongest potentiators of this behavior. Increased serotoninergic neurotransmission seems to play an important role.     

Population pharmacokinetic/pharmacodynamic (PK/PD) modelling of the hypothalamic-pituitary-gonadal axis following treatment with GnRH analogues

AIMS: To develop a population pharmacokinetic/pharmacodynamic (PK/PD) model of the hypothalamic-pituitary-gonadal (HPG) axis describing the changes in luteinizing hormone (LH) and testosterone concentrations following treatment with the gonadotropin-releasing hormone (GnRH) agonist triptorelin and the GnRH receptor blocker degarelix. METHODS: Fifty-eight healthy subjects received single subcutaneous or intramuscular injections of 3.75 mg of triptorelin and 170 prostate cancer patients received multiple subcutaneous doses of degarelix of between 120 and 320 mg. All subjects were pooled for the population PK/PD data analysis. A systematic population PK/PD model-building framework using stochastic differential equations was applied to the data to identify nonlinear dynamic dependencies and to deconvolve the functional feedback interactions of the HPG axis. RESULTS: In our final PK/PD model of the HPG axis, the half-life of LH was estimated to be 1.3 h and that of testosterone 7.69 h, which corresponds well with literature values. The estimated potency of LH with respect to testosterone secretion was 5.18 IU l(-1), with a maximal stimulation of 77.5 times basal testosterone production. The estimated maximal triptorelin stimulation of the basal LH pool release was 1330 times above basal concentrations, with a potency of 0.047 ng ml(-1). The LH pool release was decreased by a maximum of 94.2% by degarelix with an estimated potency of 1.49 ng ml(-1). CONCLUSIONS: Our model of the HPG axis was able to account for the different dynamic responses observed after administration of both GnRH agonists and GnRH receptor blockers, suggesting that the model adequately characterizes the underlying physiology of the endocrine system.     

Vancomycin dosing assessment in intensive care unit patients based on a population pharmacokinetic/pharmacodynamic simulation

AIM

To estimate the vancomycin pharmacokinetic profile in adult ICU patients and to assess vancomycin dosages for increasing the likelihood of optimal exposure.

METHODS

Five hundred and sixty-nine concentration–time data from 191 patients were analysed using a population pharmacokinetic approach (NONMEN™). External model evaluation was made in 46 additional patients. The 24 h area under the concentration–time curve (AUC(0,24 h)) was derived from the final model. Minimum inhibitory concentration (MIC) values for S. aureus were obtained from the EUCAST database. AUC(0,24 h) : MIC ≥ 400 was considered as PK/PD efficacy index. The probability of different dosages attaining the target considering different strains of S. aureus and patient subgroups was estimated with Monte Carlo simulation.

RESULTS

Vancomycin CL showed a significant dependence on patient age and renal function whereas Cr_Se > 1 mg dl⁻¹ increased V more than twofold. For our representative ICU patient, 61 years, 73 kg, Cr_Se= 1.4 mg dl⁻¹, measured CL_Cr= 74.7 ml min⁻¹, the estimated values were CL = 1.06 ml min⁻¹ kg⁻¹ and V= 2.04 l kg⁻¹. The cumulative fraction of response for a standard vancomycin dose (2 g day⁻¹) was less than 25% for VISA strains, and 33% to 95% for susceptible S. aureus, depending on patient characteristics.

CONCLUSIONS

Simulations provide useful information regarding the initial assessment of vancomycin dosing, the conventional dosing regimen probably being suboptimal in adult ICU patients. A graphic approach provides the recommended dose for any selected probability of attaining the PK/PD efficacy target or to evaluate the cumulative fraction of response for any dosing regimen in this population.     

Acute and chronic treatment with 5-HT reuptake inhibitors differentially modulate emotional responses in anxiety models in rodents

This study investigated behavioural effects of very potent 5-HT reuptake inhibitors after acute treatment (cianopramine and citalopram), as well as after chronic treatment (cianopramine), in two behavioural models of anxiety: 1) the light/dark choice procedure in mice and 2) the elevated plus-maze test in rats. In addition, the responses of mice to novelty in a free exploration paradigm were assessed after acute administration of both drugs. A single injection of cianopramine or citalopram increased neophobic reactions in the free exploration test. Furthermore, these drugs increased the avoidance reaction to a brightly illuminated chamber in the light/dark choice procedure as well as to open arms in the elevated plus-maze test. In contrast, after chronic treatment (10 mg/kg IP, once daily for 21 days) of cianopramine, anxiogenic-like effects were no longer produced in the light/dark choice paradigm whereas in the elevated plus-maze test, anxiolytic-like effects appeared. These results shed more light on the 5-HT hypothesis of anxiety, insofar as the increased availability of 5-HT resulting here from reuptake inhibition seems to initially result in an increased emotional reactivity which, however, subsequently disappears during chronic treatment.     

Further evidence for the importance of 5-HT1A autoreceptors in the action of selective serotonin reuptake inhibitors

The clinical efficacy of antidepressants that block serotonin (5-hydroxytryptamine, 5-HT) reuptake may be restrained by indirect activation of autoreceptors. In vivo microdialysis in rat hippocampus was used to assess the release-inhibitory properties of the 5-HT reuptake inhibitors citalopram and paroxetine. When reuptake was first blocked by infusing citalopram into the hippocampus, systemic administration of citalopram or paroxetine resulted in a 50–70% decrease in hippocampal 5-HT overflow. This presumably reflected the inhibition of 5-HT release subsequent to reuptake blockade in the raphe nuclei and, in turn, activation of somatodendritic autoreceptors. In support, pretreatment with (±)-pindolol or(+)-WAY100135 ((+)-N-tert-butyl-3-(4- (2-methoxyphenyl)piperazine-1-yl)-2-phenylpropanamide dihydrochloride), to block 5-HT_1A autoreceptors, abolished the decrease in 5-HT produced by systemic injection of the uptake blockers.     

Effect of chronic administration of selective 5-hydroxytryptamine and noradrenaline uptake inhibitors on a putative index of 5-HT2C/2B receptor function

Chronic treatment with selective 5-HT reuptake inhibitors (SSRI) are therapeutic in obsessive compulsive disorder, depression, anxiety, bulimia nervosa and migraine. In the present study the possibility that SSRI's act by desensitizing 5-HT_2C/5-HT_2B receptors was assessed using a putative in vivo model of 5-HT_2C/5-HT_2B receptor function, mCPP-induced hypolocomotion. mCPP (2,4 and 6 mg/kg i.p. 20 min pretest) reduced locomotion and rears in rats treated acutely or chronically with saline. Acute oral administration of the SSRI's fluoxetine (10 mg/kg), paroxetine (10 mg/kg), or clomipramine (70 mg/kg) or the noradrenaline reuptake inhibitor, desipramine (10 mg/kg), all 1 hr pretest, did not prevent mCPP-induced hypolocomotion. In contrast, chronic treatment with the SSRI's paroxetine and fluoxetine (both 10 mg/kg p.o. daily × 21 days), significantly attenuated the effect of mCPP (4 and 6 mg/kg i.p.) on locomotion and rears 24 hr after the last pretreatment dose. Chronic clomipramine (70 mg/kg p.o. daily × 21 days) also significantly attenuated the effect of mCPP (4 mg/kg i.p.) on rears and tended to reduce the hypolocomotor response. However, chronic treatment with desipramine, (10 mg/kg p.o.daily × 21) had no effect on any of the parameters measured. As chronic fluoxetine and paroxetine did not reduce brain mCPP levels (determined by HPLC 30 min after 4 mg/kg i.p.) the results suggest that chronic SSRI's, but not desipramine, reduce 5-HT_2C/5-HT/_2B receptor responsivity. If this occurs in man, it may mediate or contribute to their reported therapeutic efficacy in depression, anxiety, bulimia, migraine and alcoholism. It may also be of particular relevance to their unique efficacy in OCD.     

Inhibition of 5-HT cell firing in the DRN by non-selective 5-HT reuptake inhibitors: studies on the role of 5-HT1A autoreceptors and noradrenergic mechanisms

Improved clinical antidepressant efficacy may result if the acute inhibition of 5-HT cell firing induced by antidepressants is prevented. Here we examined whether inhibition of 5-HT cell firing by non-selective 5-HT uptake inhibiting antidepressant drugs is reversed by a selective 5-HT_1A receptor antagonist. In addition, we examined whether concomitant blockade of NA uptake offsets the inhibition of 5-HT cell firing resulting from 5-HT uptake blockade. Antidepressants which block 5-HT uptake (paroxetine, clomipramine, amitriptyline, venlafaxine), all caused dose-dependent and complete inhibition of 5-HT cell firing. Desipramine, a selective NA uptake blocker, caused a slight reduction in firing. The selective 5-HT_1A receptor antagonist, WAY 100635, reversed the inhibition of 5-HT cell firing induced by clomipramine, amitriptyline, venlafaxine, and paroxetine, but not that induced by the α₁ adrenoceptor antagonist, prazosin. Desipramine, at a dose which increased extracellular NA in the DRN, reversed the effect of prazosin but did not alter the ability of paroxetine to inhibit 5-HT cell firing. Our data indicate that antidepressant drugs with 5-HT uptake blocking properties inhibit 5-HT cell firing via activation of 5-HT_1A autoreceptors, and do so irrespective of their effects on NA uptake. These data are discussed in relation to the application of 5-HT_1A receptor antagonists to enhance the clinical efficacy of antidepressant drugs. Received: 15 July 1996 / Final version: 11 November 1996     

Clinical pharmacokinetic/pharmacodynamic profile of linezolid in severely ill intensive care unit patients

Severely ill Intensive Care Unit (ICU) patients have an increased risk of developing multiresistant Gram-positive infections, largely due to the inappropriate use of antimicrobials. In this study, the pharmacokinetic/pharmacodynamic (PK/PD) profile of linezolid, an antibiotic against Gram-positive infections, was characterised in eight critically ill patients admitted to the ICU. Remarkable variation amongst patients in the PK parameters of linezolid was observed, including a 5-7-fold difference in peak serum concentration (C_max) (mean ± standard deviation 15.70 ± 6.58 mg/L) and 12-h area under the serum concentration-time curve (AUC_0-12) (96.73 ± 56.45 mg h/L), although the minimum inhibitory concentration (MIC) was similar amongst patients. In particular, variation amongst patients was found in the ratio of AUC_0-24/MIC (range 31.66-216.82, mean 96.73) and the percentage of time that the serum concentration exceeded the MIC (T > MIC) (range 53.4-100%), two parameters used to predict linezolid efficacy. These variations highlight the importance of individual monitoring of linezolid PK/PD properties in critically ill patients. Furthermore, it was observed that regardless of AUC_0-24/MIC and T > MIC values, the clinical and microbiological responses of patients were primarily affected by the individual's pathophysiological condition. In summary, these findings point to highly variable PK/PD properties of linezolid in severely ill patients, providing the rationale for targeting linezolid dosage to each individual patient's specific properties. An optimal dosage regimen based on individual PK/PD properties and pathophysiological conditions will help reduce the occurrence of resistance in Gram-positive bacteria.     

肠促胰岛素相关药物的药代动力学／药效学模型研究进展

肠促胰岛素是一类在食物刺激下由肠道L细胞分泌并能促使胰岛素分泌的激素,其主要包括胰高血糖素样肽－1（ GLP－1）受体激动剂类似物和二肽基肽酶－4（DPP－4）抑制剂。药代动力学／药效学（PK／PD）结合模型可以为肠促胰岛素相关药物的治疗和临床研究提供有力的工具,同时,基于机制的模型可以更好地预测给药后的生理学特点和不同给药方案的治疗结果,有利于该类药物新药研发及给药方案的调整。本文主要针对 GLP －1受体激动剂类似物和DPP－4抑制剂代表药物基于其作用机制的PK／PD模型进行综述。     

Effects of selective serotonin reuptake inhibitors on intraocular pressure and anterior segment parameters in open angle eyes

Purpose: To evaluate the short- and long-term effects of selective serotonin reuptake inhibitors (SSRIs) on intraocular pressure (IOP) and anterior segment parameters in open angle eyes.

Materials and methods: This cross-sectional study included 325 eyes of 166 subjects. Subjects were divided into three groups: Group 1 included 116 eyes of 58 patients receiving SSRIs for 1?week–6?months, Group 2 included 102 eyes of 53 patients receiving SSRIs for longer than 6?months and Group 3 included 107 eyes of 55 healthy subjects not receiving any drugs. All of the patients receiving SSRIs were diagnosed as major depressive disorder. All groups were chosen to be similar in terms of age and gender. All patients underwent a detailed ophthalmologic examination including IOP measurement by Goldmann applanation tonometer and gonioscopy. Anterior segment parameters including pupil diameter (PD), central corneal thickness (CCT), anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA) were assessed by a Scheimpflug system.

Results: Pupil diameter was significantly larger in patients receiving SSRIs for <6?months and ≥6?months than the control subjects (3.53?±?0.71?mm, 3.48?±?0.60?mm versus 3.11?±?0.72?mm, p?p?Conclusions: Selective serotonin reuptake inhibitors cause mydriasis which is persistent during the treatment. In depression patients with open angle eyes, short- and long-term use of SSRIs leads to decrease in IOP.     

In vitro pharmacokinetic/pharmacodynamic activity of NXL103 versus clindamycin and linezolid against clinical Staphylococcus aureus and Streptococcus pyogenes isolates

NXL103 (linopristin/flopristin, 30/70) is a novel oral streptogramin combination with activity against a large variety of multidrug-resistant Gram-positive pathogens. The objective of this study was to evaluate the in vitro activity of NXL103 in comparison with oral comparators (clindamycin and linezolid). Six clinical isolates [four meticillin-resistant Staphylococcus aureus (MRSA) and two Streptococcus pyogenes] were exposed for 48 h in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model at a starting inoculum of ca. 10⁶ colony-forming units (CFU)/mL. Antimicrobial simulations included NXL103 500 mg every 12 h, linezolid 600 mg every 12 h and clindamycin 450 mg every 6 h. Bactericidal and static effects were defined as ≥3 log₁₀ and <3 log₁₀ CFU/mL kill from the starting inoculum, respectively. Experiments were performed in duplicate to ensure reproducibility, and differences between regimens were evaluated by analysis of variance (ANOVA) with Tukey's post-hoc test. NXL103 exhibited lower minimum inhibitory concentrations than comparators, with values ≤0.06 mg/L for S. pyogenes and 0.125-0.25 mg/L for MRSA isolates. In the PK/PD model, NXL103 demonstrated significantly better activity than linezolid and clindamycin (P < 0.05), achieving sustained bactericidal activity within <2 h against S. pyogenes strains and between 7.3-32 h against MRSA isolates. In contrast, linezolid only exhibited a static effect, whereas clindamycin achieved 3 log₁₀ kill at 6 h against the unique clindamycin-susceptible S. pyogenes strain evaluated. In conclusion, at therapeutic concentrations NXL103 exhibits promising activity against both MRSA and S. pyogenes strains, including clindamycin-resistant organisms. Further in vitro and in vivo experiments are warranted to explore the therapeutic benefit of NXL103 for the treatment of Gram-positive skin and soft-tissue infections.     

Pharmacokinetic/pharmacodynamic analyses of chymase inhibitor SUN13834 in NC/Nga mice and prediction of effective dosage for atopic dermatitis patients

A chymase inhibitor SUN13834 has been shown to improve skin condition in animal models for atopic dermatitis. In the present study, effective dosages of SUN13834 for atopic dermatitis patients were predicted by pharmacokinetic/pharmacodynamic (PK/PD) analyses of SUN13834 in NC/Nga mice, which spontaneously develop atopic dermatitis-like skin lesions. For the PK/PD analyses, we utilized the minimum effective plasma concentration of unbound SUN13834 in late-phase reaction of trinitrochlorobenzene (TNCB)-induced biphasic dermatitis in mice, based on the assumption that the minimum effective plasma concentrations are the same among the two animal models. In late-phase reaction of biphasic dermatitis, SUN13834 was most effective when its plasma concentration was highest at the elicitation, and the minimum effective plasma concentration of unbound SUN13834 at the elicitation was calculated to be 0.13–0.2 ng/mL. Oral administration of SUN13834 improved dermatitis in NC/Nga mice at 15 mg/kg (twice a day; bid) and 30 mg/kg (once a day; qd), but not at 60 mg/kg (every other day; eod). At the three dosages, the duration times over the plasma level of 0.13–0.2 ng/mL were 16.1–20.3, 10.7–12.2 and 7.8–8.8 h, respectively, suggesting an importance of maintenance of the minimum effective plasma concentration for at least about 10–12 h. The clinical effective dosage predicted in this paper is also discussed in relation to a recently conducted Phase 2a study.     

Pharmacokinetic/pharmacodynamic modelling of 2-acetyl-4(5)-tetrahydroxybutyl imidazole-induced peripheral lymphocyte sequestration through increasing lymphoid sphingosine 1-phosphate

1. 2-Acetyl-4(5)-tetrahydroxybutyl imidazole (THI) has been shown to reduce rodent peripheral blood lymphocytes through increasing lymphoid sphingosine 1-phosphate (S1P) by inhibiting S1P lyase. The objective of this study was to characterize the relationship between systemic THI exposure, splenic S1P concentrations, and lymphopenia in rats.

2. Following the oral administration of 10 and 100?mg kg^?1 THI to male rats, THI was rapidly absorbed and reached a plasma peak level at 1?h post-dosing. Splenic S1P increased and reached the peak level at 24?h. Blood lymphocyte count decreased as the splenic S1P level increased. THI plasma concentration was linked to splenic S1P concentration using an indirect model incorporated with a four-step signal transduction model. In turn, the S1P level was directly coupled with blood lymphocyte number. The integrated model simultaneously captured the splenic S1P and blood lymphocyte responses.

3. This pharmacokinetic–biomarker–pharmacodynamic model resolved the remarkable discrepancy between plasma THI concentration and the pharmacological response and quantitatively described the relationship of THI exposure, S1P, and lymphopenic response.

     

Effects of antidepressant drugs,selective noradrenaline-or 5-hydroxytryptamine uptake inhibitors,on apomorphine-induced hypothermia in mice

Antidepressant drugs which are selective noradrenaline (NA) uptake inhibitors (desipramine, maprotiline, oxaprotiline, talsupram: 0.625–10 mg/kg) antagonized dose-dependently hypothermia induced by 16 mg/kg apomorphine (APO) in mice. Of the two stereoisomers of oxaprotiline, only that inhibiting NA uptake was active. Antidepressants which are selective 5-hydroxytryptamine (5-HT) uptake inhibitors (citalopram, fluvoxamine: 2.5–40 mg/kg) did not affect APO (16 mg/kg)-induced hypothermia. Neither NA nor 5-HT uptake inhibitors counteracted hypothermia induced by 1 mg/kg APO, a dose which is easily antagonized by low doses of dopamine receptor blockers. The antagonistic action of desipramine towards APO (16 mg/kg)-induced hypothermia was prevented by phenoxybenzamine, prazosin and (-)-propranolol, while (+)-propranolol and cyproheptidine were inactive. St 587 (an alpha₁-adrenoceptor agonist) or salbutamol (an agonist of beta-adrenoceptors) attenuated APO (16 mg/kg)-induced hypothermia: given jointly, the drugs completely reversed it.m-CPP, a 5-HT receptor agonist, did not affect APO (16 mg/kg)-induced hypothermia. In conclusion, the antagonistic action of antidepressant drugs towards APO (16 mg/kg)-induced hypothermia in mice did not reflect their antidepressant properties, dopamine antagonism or their action on 5-HT receptors, only their effects on the NA uptake and/or NA transmission. Both alpha₁ and beta-adrenoceptors are involved in this antagonistic action.The results were presented at the IUPHAR 9th International Congress of Pharmacology, London, 29 July–3 August, 1984 Former name: Halina Kwiatek     

Reversal of learned helplessness by selective serotonin reuptake inhibitors in rats is not dependent on 5-HT availability

Serotonin (5-HT) and 5-HT(1A) receptors have been suggested to play a pivotal role in the mechanism of action of antidepressant drugs, particularly in the case of selective serotonin reuptake inhibitors (SSRIs). In the rat learned helplessness (LH) paradigm, a valid animal model of human depression, repeated treatment with the 5-HT(1A) receptor agonist 8-OH-DPAT (0.125 and 0.5mg/kg) and several classes of antidepressants such as the tricyclic agent desipramine (30 and 60mg/kg), the monoamine oxidase inhibitor (MAOI) pargyline (60mg/kg) and the SSRIs fluoxetine (15 and 30mg/kg), paroxetine (15 and 30mg/kg) and sertraline (30mg/kg) improved behavioural deficit in helpless rats. The involvement of serotonergic mechanisms in the antidepressant-like effect of these agents was investigated using the selective 5-HT(1A) receptor antagonist WAY 100,635 and the 5-HT synthesis inhibitor p-chlorophenylalanine (PCPA). Pretreatment with WAY 100,635 blocked the 8-OH-DPAT-induced reduction in escape failures, but did not counteract the antidepressant effect of fluoxetine and paroxetine. PCPA given alone did not modify helpless behaviour nor did it affect the behavioural effect of 8-OH-DPAT, fluoxetine and paroxetine. Adaptive changes in 5-HT(1A) receptor function were studied by measuring 8-OH-DPAT-mediated hypothermia and lower lip retraction (LLR) in the animals 24h after LH test session. Fluoxetine and paroxetine treatments caused a marked reduction in agonist-induced responses, an effect completely prevented by WAY 100,635 and PCPA. In conclusion, whereas direct agonist activity at postsynaptic 5-HT(1A) receptors attenuated helpless behaviour, the antidepressant-like effect of SSRIs was found to be independent of their actions on either 5-HT(1A) receptor function or extracellular 5-HT.     

Evaluation of ceftriaxone dosing regimens based on PK/PD models and Monte Carlo simulations

In the present study, we optimized the ceftriaxone dosing regimens based on pharmacokinetic/pharmacodynamic (PK/PD) principles using Monte Carlo simulation (MCS). Based on PK/PD theory, MCS was performed using Crystal Ball software combining PK and PD parameters with 10 000 simulation runs to calculate the probability of target attainment (PTA) and cumulative fraction of response (CFR) for the seven clinically common dosing regimens of ceftriaxone (1 g qd, 1.5 g qd, 1 g bid, 2 g qd, 1 g tid, 1.5 g bid, and 2 g bid). A %fT ≥ 50 as the target value expected to achieve satisfactory clinical efficacy and a dosing regimen with an obtained CFR ≥ 90% or the ability to achieve the highest PTA was used as a reasonable choice for empirical antimicrobial therapy, i.e. the clinically optimal regimen. All eight pathogenic bacteria had a CFR > 90% when the dosing regimen was 2 g bid and 1 g tid, seven pathogenic bacteria had a CFR > 90% when the dosing regimen was 1 g bid and 1.5 g bid, except for Pseudomonas aeruginosa, and all pathogenic bacteria had a CFR< 90% when the dosing regimen was 1 g qd and 1.5 g qd. The dosing regimens of 2 g bid and 1 g tid were effective against all eight pathogenic bacteria infections, and 1 g bid and 1.5 g bid dosing regimens were effective against the other seven pathogenic bacteria except for Pseudomonas aeruginosa.     

Effects of co-administration of a selective serotonin reuptake inhibitor and monoamine oxidase inhibitors on 5-HT-related behavior in rats

5-hydroxytryptamine (5-HT) syndrome is a dangerous condition of 5-HT excess that can occur in the case of co-administration of a monoamine oxidase (MAO) inhibitor and a serotonin reuptake inhibitor (SSRI). The goal of the present study was to investigate the effects of acute administration of MAO inhibitors and subchronic administration of fluvoxamine on 5-HT-related behaviors (head shaking and 5-HT syndrome) in rats treated with 5-hydroxytryptophan (5-HTP). Administration of the non-selective MAO inhibitor, pargyline, and the selective MAO-A inhibitor, clorgyline, resulted in 5-HT syndrome in 5-HTP-treated rats, and subchronic co-administration of fluvoxamine intensified the syndrome. However, administration of the selective MAO-B inhibitor, selegiline, did not induce 5-HT syndrome with or without subchronic fluvoxamine co-administration. These data suggest that non-selective MAO and selective MAO-A inhibitors can induce 5-HT syndrome in humans when co-administered with SSRI. Further, the risk of 5-HT syndrome may be lower with the selective MAO-B inhibitor, selegiline.     

Current status and future perspective on preclinical pharmacokinetic and pharmacodynamic (PK/PD) analysis: Survey in Japan pharmaceutical manufacturers association (JPMA)

Preclinical pharmacokinetic/pharmacodynamic (PK/PD) analysis is an efficient tool for the translational research and proof of mechanism/concept in animals. The questionnaire survey on the practice of preclinical PK/PD analysis was conducted in the member companies of the Japan Pharmaceutical Manufacturers Association (JPMA). According to the survey, 60% of companies conducted preclinical PK/PD analysis and its impact for drug development was different between each of the companies. The frequently analyzed therapeutic areas of preclinical PK/PD analysis were neurology, inflammation and metabolic disease, and those are different from the therapeutic area (infectious disease and oncology) in which PK/PD analysis was considered as effective by the present survey. Many companies which have used preclinical PK/PD analysis for the translation to human PK/PD and for the prediction of dose/regimen had good communication with other research & development (R&D) departments (e.g. pharmacology/clinical pharmacology). The increase in resources for preclinical PK/PD analysis including education was highly demanded. As a future perspective, the closer collaboration between pharmacokinetics scientists, pharmacologists, toxicologists and clinical pharmacologists and the increase in resources including upskilling and the comprehension of preclinical PK/PD analysis by the project team are considered to lead to efficient contributions to improve the success ratio of drug discovery and development.