Pharmacokinetics of methysergide and its metabolite methylergometrine in man

Summary Five healthy men were given 1.0 mg methysergide maleate intravenously and 2.7 mg methysergide maleate orally in a cross-over study.The systemic availability of methysergide was only 13%, most probably due to a high degree of first-pass metabolism to methylergometrine. We also found evidence of extrahepatic clearance of methysergide.After oral administration the plasma concentrations of the metabolite were considerably higher than those of the parent drug and the area under the plasma concentration curve (AUC) for methylergometrine was more than ten times greater than for methysergide.Our findings may be relevant to the treatment of migraine if methylergometrine contributes to the effect of methysergide.Methylergometrine had a significantly longer elimination half-life than methysergide (223±43 min vs 62.0±8.3 min and 174±35 min vs 44.8±8.1 min in the oral and intravenous studies respectively).     

Pharmacokinetics of flobufen and its main active metabolite in the rat

Pharmacokinetic study of the anti-inflammatory [3H] flobufen (I) and its active metabolite (II) has been carried out in rats given po and iv doses of 2, 10, and 50 mg/kg I and equimolar doses of II. Various pharmacokinetic parameters of I and II [dose normalized AUC; mean residence time (MRT); systemic blood clearance; steady state volume of distribution, (Vss)] are dose-independent. I is completely absorbed from the gastrointestinal tract and is rapidly (MRT = 7.2 hr) converted to II, which is slowly (MRT = 2.6 days) eliminated from the blood. The fraction of total blood clearance that forms II is 0.83 following iv dose of I. The Vss of the less lipophilic metabolite II is somewhat lower (0.36-0.46 liters/kg) than that of the parent drug (0.51-0.56 liters/kg).     

Pharmacokinetics of triamterene and its metabolite in man

The pharmacokinetic profiles of triamterene and hydroxytriamterene sulfuric acid ester, the major metabolite of triamterene, were studied in six normal male volunteers using a newly developed specific HPLC analytical method. Following a 100 mg oral dose of triamterene, the plasma concentration time course of the sulfate conjugate parallels that of triamterene in all subjects, but concentrations of the metabolite were more than 10 times higher than unchanged triamterene concentrations at identical sampling times. Interestingly, the renal clearance of the sulfate conjugate was less than that of triamterene. These characteristic features of triamterene disposition were fitted to a compartment model incorporating a first-pass metabolic process. Unbound fractions of triamterene and metabolite in plasma were 0.39 and 0.10 (mean of 6 subjects), respectively. The low unbound fraction of the metabolite in plasma most probably accounts for the low renal clearance of the sulfate conjugate as compared with triamterene.Supported in part by NIH Grant AM20884 and funds from Mylan Pharmaceuticals.     

Pharmacokinetics of methylergometrine (methylergonovine) in the rabbit and man

Methylergometrine concentrations in human and rabbit plasma were determined by a new radioimmunoassay after a single intravenous injection (0.2 mg in man and 0.05, 0.1 and 0.2 mg/kg in rabbits). Both in man and in the rabbit methylergometrine disappeared quickly from the plasma with a mean T1/2alpha of 1.8 and 1.2-1.7 min. respectively. Similarly, the T1/2beta-values were 32.1 and 27.3-93.2 min. tthe mean maximal response in the rabbit uterus in situ after 0.05, 0.1 and 0.2 mg/kg intravenously dose was found at 40 sec., 26 sec., and 26 sec. after the drug administration, respectively, and the dose response curve was quite steep. A significant correlation was found between the dose and response.     

甲胺及其代谢产物甲醛在动物体内的药代动力学

目的进一步了解血浆氨基脲敏感型胺氧化酶(SSAO)活性与内源性甲醛的生理学与病理学意义。方法采用高效液相色谱法测定小鼠、大鼠和兔血浆中SSAO活性和静脉给予甲胺后甲胺及其代谢产物甲醛浓度。结果小鼠、大鼠和兔血浆中SSAO活性分别为(4.1±1.0),(2.0±0.3)和(325.8±3.9)μmol·h-1·L-1。3种动物单次iv甲胺后,甲胺的分布和代谢迅速。小鼠单次iv4.2mg·kg-1甲胺后甲醛浓度在代谢初期缓慢上升,在20~40min达峰后缓慢消除。而大鼠单次iv4.2mg·kg-1甲胺后血浆甲醛浓度无明显改变。兔单次iv2.3,9.6和36.8mg·kg-1甲胺后,甲胺AUC与剂量不成比例,Cl随剂量增加明显减少,呈非线性动力学特征。甲醛在兔体内消除较快,甲醛AUC与甲胺剂量的比值和全身清除率Cl无明显差异,但ke随给予甲胺剂量的增大而减少,t1/2显著延长。结论甲胺在3种动物间代谢情况相似,其代谢产物甲醛则明显不同。甲胺给予剂量的不同可能导致甲胺代谢动力学的改变,进而可能影响甲醛的代谢。     

Pharmacokinetics of pirprofen and its pyrrol metabolite in elderly patients

Summary Plasma concentrations of pirprofen and of its pyrrol metabolite were assessed in 9 elderly patients (3 males, 6 females; mean age 76 years) suffering from chronic degenerative disease. Pirprofen 400 mg in 4 ml was administered i.m. and the pharmacokinetic profile of the drug and the metabolite was calculated.The AUC, C_max and t_1/2 of pirprofen were similar to those found in previous studies, and, as expected, those parameters for the pyrrol metabolite were lower (C_max=2.8 µg/ml^–1; t_max=6.4 h; AUC(0–32)=56.5 µg · h · ml^–1). One patient (n=8) showed different pharmacokinetic behaviour, which is discussed.The data suggest that age has little influence on the pharmacokinetic of pirprofen, although unpredictable responses should always be considered in clinical practice.     

Pharmacokinetics of tetrabenazine and its major metabolite in man and rat. Bioavailability and dose dependency studies

The pharmacokinetics of tetrabenazine (TBZ), a catecholamine and serotonin depletor, and its major metabolite, dihydrotetrabenazine (HTBZ), were studied in four patients affected by tardive dyskinesia, who were under treatment with different doses of TBZ (12.5-37.5 mg, t.i.d.), and in the rat. In the patients, the steady-state area under the plasma concentration-time curves (AUCs) of the metabolite were 82.6-199-fold higher than those of TBZ. The drug showed a small and erratic bioavailability (F = 0.06 +/- 0.026, mean +/- SD). It appears to be extensively metabolized, as no unchanged TBZ could be detected in the urine of the patients. Single oral doses of 0.5-10 mg/kg and single iv dose of 1 mg/kg of TBZ were each administered to four to six rats. The clearance of the drug following iv administration to the rat (mean +/- SD, 58.9 +/- 6.01 ml X min-1 X kg-1) was very close to the rat hepatic blood flow indicating a perfusion-limited clearance. An F value of 0.17 was obtained following iv and po doses of 1 mg/kg TBZ in the rat. The oral absorption of TBZ seems to be rapid and almost complete. Plots of the AUCs of TBZ and HTBZ vs. five different po doses (0.5-10 mg/kg) were linear with correlation coefficients of 0.998 and 0.986 for TBZ and HTBZ, respectively, suggesting linear kinetics in the examined dosage range. In both the patients and rats, the plasma profile of TBZ followed characteristics of a multiexponential pharmacokinetic model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of desethylamiodarone in the rat after its administration as the preformed metabolite, and after administration of amiodarone

The pharmacokinetics of desethylamiodarone (DEA), the active metabolite of amiodarone (AM), were studied in the rat after administration of AM or preformed metabolite. Rats received 10 mg/kg of either intravenous or oral AM HCl or DEA base. Blood samples were obtained via a surgically implanted jugular vein cannula. Plasma concentrations were measured by a validated LC/MS method. In all AM treated rats, AM plasma concentrations greatly exceeded those of the formed DEA. The fraction of AM converted to DEA after i.v. administration was 14%. Amiodarone had a significantly lower (approximately 50%) clearance than DEA, although the volume of distribution and terminal phase half-life did not differ significantly. The hepatic extraction ratio of DEA was 0.48, similar to that of AM (0.51). Oral AM demonstrated higher plasma AUC (5.6 fold) and higher C(max) (6.1 fold) than oral DEA and oral bioavailability of AM (46%) was greater than DEA (17%). The estimated fraction of the oral dose of AM converted to DEA was 4.5 fold higher than after i.v. administration, suggesting first-pass formation of DEA from AM. Amiodarone and DEA differed in their pharmacokinetic characteristics mostly due to a higher CL of DEA. With oral dosing, AM appeared to undergo significant presystemic first-pass metabolism within the intestinal tract.     

Pharmacokinetics of cimetidine and its sulphoxide metabolite during haemodialysis

Summary A single intravenous dose of cimetidine 200mg was administered to 6 patients with severe chronic renal failure one hour prior to haemodialysis. The plasma concentrations of cimetidine and its sulphoxide metabolite at the start of haemodialysis were 2.74±0.12 and 0.76±0.08 µg/ml, and after dialysis for 4h 1.08±0.10 and 0.51±0.08 µg/ml, respectively (mean ± SE). The average haemodialysis clearance (Cl_HDa) of cimetidine during dialysis was 46–92ml/min at a dialysate flow rate of 320ml/min and blood flow rates in the 6 patients between 160–240ml/min. The mean Cl_HDa of the sulphoxide metabolite was 44% higher than that of cimetidine, and ranged between 49–148ml/min. During haemodialysis the mean plasma elimination half-life (t_1/2) of cimetidine was 3.24h (range 2.08–5.08) and of the sulphoxide metabolite 9.49h (range 4.70–14.39). There was a significant relationship between the elimination rate constant () and Cl_HDa of the sulphoxide metabolite (p<0.01), but no such relationship was found between and Cl_HDa of cimetidine. However, there was a tendency to a relationship between of cimetidine and the capacity to metabolise the drug, expressed as the ratio between the plasma concentrations of the sulphoxide metabolite and cimetidine after dialysis for 4h. These ratios ranged between 0.23–0.76, and the lowest ratio was seen in the patient with the lowest value of cimetidine. Thus, the large variations in the plained by differences in their capacity to metabolise the drug. The mean total amount of cimetidine eliminated during dialysis was 27.3mg (range 17.9–31.8), which was 9.0–15.9% of the given dose. Between 12.2–21.2mg (mean 15.3) of the sulphoxide metabolite was eliminated in the dialysate. Major adjustment of the dose of cimetidine on days of dialysis is not necessary.     

Pharmacokinetics of budesonide and its major ester metabolite after inhalation and intravenous administration of budesonide in the rat.

Fatty acid esterification of budesonide (BUD) has previously been documented in vitro as well as in large airway tissues after in vivo administration. This reversible esterification has the potential to prolong the anti-inflammatory effect of BUD and improve its airway selectivity. In the present study we characterized the plasma and tissue kinetics of BUD in the rat after inhalation and intravenous administration, and fitted a semiphysiological compartment model to the data. After inhalation, BUD half-life was longer (8.2 h) in trachea than in plasma (3.7 h), with similar data after intravenous dosing. BUD-oleate was formed in all tissues and had a longer half-life than BUD in trachea (18-20 h) but a similar half-life in plasma and muscle. Although the major fraction of BUD and BUD-oleate in the body was found in muscle, the airways, especially trachea, possessed a high capacity to form BUD-oleate. According to steady-state simulations, BUD-oleate accumulated in trachea, giving rise to persistent and higher concentrations of active BUD as compared with a situation wherein esters were not formed. BUD esters had no effect on plasma levels of BUD at steady state, however. BUD and BUD-oleate were shown to have a 2-fold and 10- to 50-fold selectivity, respectively, in airways as compared with muscle tissue after intravenous administration. After inhalation, the corresponding figures for selectivity were 10 and 50 to 1000, respectively.     

Pharmacokinetics of methadone and its primary metabolite in 20 opiate addicts

In a closed metabolic ward the pharmacokinetics of methadone and its primary metabolite (EDDP) were studied in 20 long-term opiate addicts. After administration of the daily oral dose of methadone HCl (mean 60 mg, range 10–225 mg) blood samples were taken and analysed, using a newly developed high-performance liquid chromatography (HPLC) method. The steady-state plasma concentrations of the 20 subjects varied from 65–630 ng·ml^–1 and from 5 to 55 ng·ml^–1, whereas the peak concentrations were 124–1255 ng·ml^–1 and 10 – 301 ng·ml^–1 for methadone and EDDP, respectively. The calculated ratios between the area under the curve (AUC_{(0–24 h)}) for methadone and the AUC_{(0–24 h)} for EDDP varied from 5.9 to 44.6, indicating interindividual differences in metabolic activity. In 19 out of 20 subjects the pharmacokinetics of methadone are best described using a two-compartment model. The mean body clearance was 1.64 ml·min^–1·kg^–1, whereas the mean elimination rate constant () and plasma half-life (t _1/2) were 0.026·h^–1 (range 0.013–0.053·h^–1) and 31.2 h (range 13–53 h), respectively. Differences of gender were also found. A poor correlation was found between the methadone dose and the steady-state level. A much better correlation was found between the normalized steady-state level and the body clearance.     

Pharmacokinetics of propentofylline and the quantitation of its metabolite hydroxypropentofylline in human volunteers

Propentofylline (PPF, 3-methyl-1-(5-oxohexyl)-7-propylxanthine) has been reported to be effective for the treatment of both vascular dementia and dementia of the Alzheimer type. The pharmacological effects of PPF may be exerted via the stimulation of nerve growth factor, increased cerebral blood flow, and inhibition of adenosine uptake. The objectives of this experiment are to determine the kinetic behavior of PPF, to identify, and to quantify its metabolite in human. Blood samples were obtained from human volunteers following oral administration of 200 mg of PPF tablets. For the identification and quantification of the metabolite, 3-methyl-1-(5-hydroxyhexyl)-7-propylxanthine (PPFOH), PPFOH was synthesized and identified by gas chromatography/mass spectroscopy (GC/MS) and¹H-nuclear magnetic resonance spectroscopy. The molecular weight of synthesized metabolite is 308 dalton. The PPF and PPFOH in plasma were extracted with diethyl ether and identified by electron impact GC/MS. The plasma concentrations of PPF and PPFOH were determined by gas chromatography/nitrogen phosphorus detector in plasma and their pharmacokinetic parameters were determined. The mean half-life of PPF was 0.74 hr. The areas under the curve (AUCs) of PPF and PPFOH were 508 and 460 ng.hr/ml, respectively. C_max of PPF was about 828.4 ng/ml and the peak concentration was achieved at about 2.2 hr (T_max). These results indicate that PPF is rapidly disappeared from blood due to extensive metabolism into PPFOH.     

Pharmacokinetics of triflusal and its main metabolite in rats and dogs.

The methods for determining plasma concentrations of triflusal (2-acetoxy-4-trifluoromethyl benzoic acid) that have been described, do not distinguish between the drug and its main metabolite HTB (2-hydroxy-4-trifluoromethyl benzoic acid). In the present study, we have developed a new analytical technique based on HPLC that enabled us to carry out a pharmacokinetic study of the drug and its metabolite in animals. An intravenous or oral dose of 50 mg/kg was administered to male Sprague-Dawley rats, and 15 mg/kg was administered to beagle dogs. Plasma levels of triflusal and HTB were determined. In rats, triflusal was quickly eliminated from plasma with a biological half-life (t1/2) of 2.7 min and a clearance (Cl) of 73.4 (ml/kg)/min. The elimination of HTB was much slower with a t1/2 of 21.5 h and a Cl of 5.1 (mg/kg)/h. The maximum concentration (Cmax) of triflusal in rats after an oral administration was 8.1 +/- 2.0 micrograms/ml reached between 2.5 and 10 min. The Cmax of HTB was 237.7 micrograms/ml and was achieved at 0.7 h. The bioavailability of triflusal in rats was only 10.6% while the bioavailability of HTB was more than 100% indicating an important first pass effect. In dogs the t1/2 of triflusal was 14.4 +/- 5.9 min and the Cl was 25.1 +/- 4.7 (ml/kg)/min. HTB was also eliminated very slowly with a t1/2 of 71.1 +/- 12.5 h and a Cl of 2.4 +/- 0.3 (ml/kg)/h. The Cmax of triflusal in dogs was 13.3 +/- 2.9 micrograms/ml and was reached after 19.2 +/- 6.1 min (tmax).(ABSTRACT TRUNCATED AT 250 WORDS)     

氯沙坦及其代谢物在朝鲜族和汉族健康人体内的药代动力学

目的:研究朝鲜族和汉族健康受试者口服单剂量氯沙坦钾片的药代动力学.方法:健康受试者20名(朝鲜族10名,汉族10名,男女各半),口服单剂量氯沙坦钾片剂50mg;用HPLC-荧光法测定氯沙坦及其代谢物E-3174血药浓度,采用DAS软件和SPSS软件进行数据处理和统计学分析.结果:单剂量口服50 mg氯沙坦钾片后,朝鲜族受试者的氯沙坦和E-3174的主要药动学参数如下:Cmax分别为(524±349),(493±188)ng·mL-1;tmax分别为(0.9±0.4),(2.4±0.8)h;t1/2(1.5±0.4),(3.1±0.7)h;AUC0-24分别为(682±319),(2563±752) ng·h·mL-1;AUC0-∞分别为(752±331),(2608±766)ng·h·mL-1.汉族受试者的氯沙坦和E-3174的主要药动学参数如下:Gmax分别为(351±168),(242±60)ng·mL-1;tmax分别为(1.4±1.1),(3.6±1.7)h;t1/2分别为(0.8±0.4),(4.7±1.1)h;AUC0-24分别为(498±172),(1853±194) ng·h·mL-1;AUC0-∞分别为( 523±184),(1960±182) ng-h·mL-1.结论:氯沙坦钾片在朝鲜族和汉族健康受试者体内药动学参数差异存在统计学意义,在不同性别间药动学参数差异无统计学意义,个体间药动学参数存在较大差异,临床治疗中应实行个体化给药方案.     

氯沙坦及其代谢物在蒙古族和汉族健康人体的药动学特征

目的研究蒙古族和汉族健康受试者口服单剂量氯沙坦钾片的药动学特征。方法健康受试者20名（其中蒙古族10名,汉族10名,男女各半）,口服单剂量氯沙坦钾片50mg;用HPLC荧光法测定氯沙坦及其代谢物E-3174血药浓度,DAS软件程序进行数据处理并采用SPSS软件进行统计学分析。结果蒙古族受试者单剂量口服50nag氯沙坦钾片剂后氯沙坦和E-3174的主要药动学参数分别为：ρmax（438±254）、（358±169）μg·L-1;tmax（1．6±0．9）、（3．8±1．9）h;t1/2（1．9±1．2）、（4．4±0．7）h;AUC024（859±309）、（2516±652）P-g·h·L-1;AUC0→∞（944±338）、（2603±668）μg·h·L-1。汉族受试者氯沙坦和E-3174的主要药动学参数分别为：ρmax（351±168）、（242±60）μg·L-1;tmax（1．4±1．1）、（3．6±1．7）h;t1/2（0．8±0．4）、（4．7±1．1）h;AUC0→24（497±172）、（1853±194）μg·h·L-1;AUC0→∞（523±184）、（1960±182）μg·h·L-1。结论氯沙坦钾片剂在蒙古族和汉族健康受试者体内药动学参数差异存在统计学意义,个体间药动学参数存在较大差异,临床治疗中应实行个体化给药方案,在不同性别间药动学参数差异无统计学意义。     

氯沙坦及其代谢物在维吾尔族和汉族健康志愿者的药代动力学

目的 研究维吾尔族和汉族健康受试者单剂量口服氯沙坦钾片(抗高血压药)的药代动力学特征.方法 20名健康受试者(其中维吾尔族10名,汉族10名,男女各半),单剂量口服氯沙坦钾片50 mg;用高效液相色谱-荧光法测定氯沙坦及其代谢物E-3174血药浓度,用DAS软件进行数据处理、SPSS 13.0软件进行统计学分析.结果 维吾尔族受试者单剂量口服氯沙坦钾片50 mg后氯沙坦和代谢物E-3174的主要药代动力学参数分别为:Cmax(344±153),(477±166)μg·mL-1;tmax(1.0±0.3),(2.6±0.5)h;t1/2(1.0±0.4),(2.9±0.8)h;AUG0-24h(598±216),(2243±518)μg·h·mL-1;AUC0-∞(632±242),(2429±552)μg.h·mL-1.汉族受试者单剂量口服氯沙坦钾片50 mg后氯沙坦和代谢物E-3174的主要药代动力学参数分别为:Cmax(351±168),(242±60)ng·mL-1;tmax(1.4±1.1),(3.6±1.7)h;t1/2(0.8±0.4),(4.7±1.1)h;AUC0-24h(497±172),(1853±194)ng·h·mL-1;AUC0-∞(523±184),(1960±182)ng·h·mL-1.结论 氯沙坦的代谢物E-3174的药代动力学参数t1/2、Vd、Cmax在维吾尔族和汉族健康受试者间的差异有显著性意义(P＜0.05),不同性别间药代动力学参数的差异无显著性意义(P＞0.05),所有药代动力学参数在同一民族和不同民族的个体间差异都很大,临床治疗中应实行个体化给药方案.     

Pharmacokinetics of phosphocreatine and its active metabolite creatine in the mouse plasma and myocardium

BackgroundThe pharmacokinetic (PK) studies of phosphocreatine (PCr) and its active metabolite creatine (Cr) are considerably lacking. This study is to comparatively investigate the PK profiles of PCr and Cr in mice plasma and myocardium as well as the ATP level.MethodsAfter iv administration of equimolar PCr and preformed Cr to healthy and Pit-induced myocardial ischemic mice, plasma and myocardium samples were analyzed for exogenous PCr, Cr and related ATP concentrations using a specific ion-pair reversed-phase HPLC–UV assay.ResultsThe plasma C–T data of iv PCr and Cr were well fitted to two-compartment model. Following iv PCr, Cr appeared in plasma as early as 1.0 min postdose with a longer t_1/2 than PCr and had a f_m of 72%. The mice dosed iv PCr preceded 5 min by ip Pit 30 U/kg showed longer t_{1/2β PCr} and t_{1/2 Cr} in plasma and elevated C_{max, Cr} and C_{max, ATP} in myocardium compared with mice dosed iv PCr alone, and it was estimated that about 40% ATP produced by iv PCr was from Cr.ConclusionThe PCr in plasma is converted to Cr rapidly and mostly, and shows an elimination rate limited (ERL) metabolite disposition. Iv PCr caused a significantly elevated and long-lasing myocardial ATP and Cr levels. The Pit-induced myocardial ischemia brings slower elimination of PCr and Cr and higher peak concentrations of Cr and ATP in myocardium. The metabolite Cr at least partially mediates PCr-caused rise in myocardial ATP level and also possibly the cardio-protective effects of PCr.     

Pharmacokinetics of amrubicin and its active metabolite amrubicinol in lung cancer patients

Amrubicin, a synthetic 9-aminoanthracycline agent, was recently approved in Japan for treatment of small-cell lung cancer and non-small-cell lung cancer. Amrubicin is converted enzymatically to the C-13 hydroxy metabolite amrubicinol, which is active and possesses a cytotoxicity 10 to 100 times that of the parent drug. The purpose of this study was to characterize the pharmacokinetics of amrubicin and its active metabolite amrubicinol. Amrubicin was administered on days 1-3 in 16 patients with advanced lung cancer. The pharmacokinetics analysis of amrubicin and amrubicinol was performed by high-performance liquid chromatography. When 45 mg/m amrubicin was administered in a bolus injection once every 24 hours for 3 consecutive days, the areas under the curves (0 to 72 hours) for amrubicin and amrubicinol were 13,490 and 2585 ng . h/mL, respectively. The apparent total clearance (CLapp) of amrubicin was 15.4 L/h. The area-under-the-curve ratio of amrubicinol to amrubicin was 15.1 +/- 4.6% (mean +/- SD) at doses ranging from 30 to 45 mg/m. Interindividual variability in the enzymatic conversion of amrubicin to amrubicinol was small. In contrast, a large interindividual variability in the CLapp of amrubicin was observed (CV = 49.8%). The areas under the curves of amrubicin and amrubicinol seemed to be associated with the severity of hematologic toxicities. There is a possibility that monitoring of the plasma concentrations of amrubicin and amrubicinol may provide an efficient tool for establishing the optimal dosage of amrubicin in each patient.     

Pharmacokinetics of cefotaxime and its desacetyl metabolite in plasma and in cerebrospinal fluid

The aim of the study was to investigate the pharmacokinetic modelling of Cefotaxime (CTX) and its main metabolite Desacetyl Cefotaxime (DCTX) which has a less antibacterial activity than the CTX. After intravenous administration of 1g of CTX to 26 patients, the plasma concentrations determined by HPLC showed that the pharmacokinetics of CTX and transformation to DCTX can be described with an open five-compartment model. The implications of this are discussed from the clinical point of view.     

Pharmacokinetics of intravenously administered dantrolene and its 5-hydroxy metabolite in dogs

Dantrolene, a direct acting muscle relaxant used orally for spasticity, has appeared to be effective in the prevention and treatment of malignant hyperthermia in man and animals when administered intravenously. Its pharmacokinetics following intravenous administration have been studied in dogs. Concentrations of dantrolene and its metabolites in plasma, urine, and bile were determined by high-performance liquid chromatography. Recovery of unchanged drug and reduced metabolites was negligible; of the hydroxy metabolite 2% was found in the urine and about 25% in the bile. The half-life of 5-hydroxydantrolene was shorter than that of the parent drug as demonstrated by administration of the metabolite. The apparent renal clearance of 5-hydroxydantrolene was independent of creatinine clearance, urine flow and pH, and appeared to be reduced in the presence of probenecid. Bile to plasma ratios of the hydroxy metabolite were high with biliary concentrations far exceeding the maximum solubility in water. The results of this pilot study indicate that hydroxylation is primarily responsible for the excretion of the dantrolene molecule from the body.