RESUMO
Solar cells are generally optimised for operation under AM1.5 100 mW cm(-2) conditions. This is also typically done for polymer solar cells. However, one of the entry markets for this emerging technology is portable electronics. For this market, the spectral shape and intensity of typical illumination conditions deviate considerably from the standard test conditions (AM1.5, 100 mW cm(-2), at 25 °C). The performance of polymer solar cells is strongly dependent on the intensity and spectral shape of the light source. For this reason the cells should be optimised for the specific application. Here a theoretical model is presented that describes the light intensity dependence of P3HT:[C60]PCBM solar cells. It is based on the Shockley diode equation, combined with a metal-insulator-metal model. In this way the observed light intensity dependence of P3HT:[C60]PCBM solar cells can be described using a 1-diode model, allowing fast optimization of polymer solar cells and module design.
RESUMO
In this study, the influence of the TiCl(4) post-treatment on nanocrystalline TiO(2) films as electrodes in dye-sensitized solar cells is investigated and compared to nontreated films. As a result of this post-treatment cell efficiencies are improved, due to higher photocurrents. On a microscopic scale TiO(2) particle growth on the order of 1 nm is observed. Despite a corresponding decrease of BET surface area, more dye is adsorbed onto the oxide surface. Although it seems trivial to match this finding with the improved photocurrent, this performance improvement cannot be attributed to higher dye adsorption only. This follows from comparison between incident photon to current conversion efficiency (IPCE) and light absorption characteristics. Since the charge transport properties of the TiO(2) films are already more than sufficient without treatment, the increase in short circuit current density J(SC) cannot be related to improvements in charge transport either. Transient photocurrent measurements indicate a shift in the conduction band edge of the TiO(2) upon TiCl(4) treatment. It is concluded that the main contribution to enhanced current originates from this shift in conduction band edge, resulting in improved charge injection into the TiO(2).
RESUMO
The effect of straight release carbamazepine monotherapy was studied in 12 well-controlled epileptic patients using adaptive tracking, smooth pursuit and saccadic eye movements, body sway, Digit Symbol Substitution Test (DSST) and Visual Analogue Scales. Patients were matched to healthy controls for age and gender. After patients had received their usual morning dose of carbamazepine, patient-control pairs were studied for 7 h. Compared to controls, the average DSST scores of patients were significant lower. No relationships were shown between DSST performance and plasma concentrations of carbamazepine and carbamazepine-epoxide. No significant differences were found for any of the other effect parameters. Variations in plasma concentrations were limited, contributing to the absence of systematic fluctuations in test results. Of the used tests, DSST is most clearly related to cognitive function. It is concluded that the difference in DSST performance appears to reflect a long-term small neurocognitive difference between subjects with and without epilepsy.
Assuntos
Anticonvulsivantes/farmacologia , Carbamazepina/análogos & derivados , Carbamazepina/farmacologia , Epilepsia/tratamento farmacológico , Desempenho Psicomotor/efeitos dos fármacos , Adolescente , Adulto , Anticonvulsivantes/sangue , Anticonvulsivantes/farmacocinética , Área Sob a Curva , Carbamazepina/sangue , Carbamazepina/farmacocinética , Cromatografia Líquida de Alta Pressão , Epilepsia/fisiopatologia , Epilepsia/psicologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Acompanhamento Ocular Uniforme/efeitos dos fármacos , Movimentos Sacádicos/efeitos dos fármacos , Fatores de TempoRESUMO
OBJECTIVE: The effect of oral warfarin on the pharmacokinetics and pharmacodynamics of the synthetic direct thrombin inhibitor napsagatran was investigated. METHODS: In an open, randomised, two-way crossover study, 12 healthy male volunteers were infused napsagatran (80 micrograms/min) for 48 h. Each subject was administered 25 mg warfarin (Coumadin) at the start of the infusion in either the first or second treatment period. Sampling was performed regularly over the treatment period and 24 h thereafter for measurement of plasma levels of napsagatran, activated partial thromboplastin time (APTT) and prothrombin time (PT). RESULTS: The pharmacokinetic parameters of napsagatran were not significantly influenced by co-administration of warfarin. Napsagatran administration was followed by increases in APTT and PT. Co-administration of warfarin increased the AUEC (area under the effect curve) calculated for the period 0-48 h (corrected for baseline) for APTT by 45% (95% CI: 28-65%) and for PT by 438% (95% CI: 272-678%) compared to the treatment with napsagatran alone. CONCLUSION: Warfarin has no effect on the pharmacokinetics of napsagatran, but has a marked influence on the pharmacodynamic parameters (APTT, PT) of napsagatran. In clinical practice, this interaction between the two compounds should be taken into account. The PT cannot be used to monitor the effect of oral anticoagulants during the switch from this group of direct thrombin inhibitors to full oral anticoagulant therapy.
Assuntos
Anticoagulantes/farmacocinética , Antitrombinas/farmacocinética , Naftalenos/farmacocinética , Piperidinas/farmacocinética , Varfarina/farmacocinética , Adulto , Anticoagulantes/sangue , Anticoagulantes/farmacologia , Antitrombinas/farmacologia , Área Sob a Curva , Estudos Cross-Over , Humanos , Masculino , Modelos Biológicos , Naftalenos/sangue , Naftalenos/farmacologia , Tempo de Tromboplastina Parcial , Piperidinas/sangue , Piperidinas/farmacologia , Tempo de Protrombina , Varfarina/sangueRESUMO
AIMS: Application of single methods to assess liver blood flow (LBF) yielded conflicting results on the magnitude and duration of effect on LBF of oral nifedipine and captopril. The aim of this study was to investigate the influence of these drugs on LBF by simultaneous use of ICG infusion and echo-Doppler. METHODS: The study was performed according to a double-blind, placebo-controlled, randomized, cross-over design in nine healthy male volunteers. After an overnight fast and an equilibration period, subjects received a continuous i.v. indocyanine green (ICG) infusion for 4 h. At presumed ICG steady state (t=45 min), subjects were dosed with oral nifedipine (20 mg), captopril (50 mg) or placebo. During the experiment, blood sampling for ICG assay and measurement of portal venous blood flow (echo-Doppler) took place regularly. Treatments were compared using analysis of variance. Differences are reported with 95% confidence intervals (CI). RESULTS: The area under the curves (AUC) for ICG over 1 h and over 3 h after nifedipine were 15% (difference in AUC: + 0.6, + 7.0 mg l(-1) min) and 22% (+ 7.0, + 28.4 mg l(-1) min) lower compared with placebo. After captopril, the AUC values were 8-10% lower compared with placebo but the 95% CIs included zero. Portal venous flow was 15% (+ 5, + 86 ml min(-1)) higher compared to placebo after nifedipine but not after captopril (-3%; -49, +33 ml min(-1)). The duration of effect on liver blood flow lasted approximately 2 h but was variable (range: 40-160 min). The time to maximal blood flow increase and the duration of effect after nifedipine were very similar for both measures of LBF. Changes in ICG concentrations could be reasonably well predicted from the changes in portal blood flow. CONCLUSIONS: Nifedipine increases LBF for a substantial period of time but the effect is variable between subjects. This effect could be detected by both the ICG method and echo-Doppler and the findings of both methods were in agreement. In this respect it is likely that captopril does not influence LBF in healthy volunteers as no effect was detected with either method.
Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Captopril/farmacologia , Circulação Hepática/efeitos dos fármacos , Nifedipino/farmacologia , Administração Oral , Adolescente , Adulto , Inibidores da Enzima Conversora de Angiotensina/administração & dosagem , Área Sob a Curva , Bloqueadores dos Canais de Cálcio/administração & dosagem , Captopril/administração & dosagem , Corantes/farmacocinética , Estudos Cross-Over , Método Duplo-Cego , Hemodinâmica/efeitos dos fármacos , Humanos , Verde de Indocianina/farmacocinética , Infusões Intravenosas , Masculino , Taxa de Depuração Metabólica , Nifedipino/administração & dosagemRESUMO
Potential interethnic differences in drug disposition and effects between Japanese and white subjects hamper the registration in Japan of medications already used in Western countries. This double-blind, placebo-controlled, crossover study was conducted to compare the pharmacodynamics and pharmacokinetics of a single oral dose of nitrazepam (5 mg) in age- and sex-matched Japanese (n = 8) and white (n = 8) healthy volunteers. The study was performed in centers in Japan and the Netherlands using the same methods and study design. Subjects were individually matched for gender, age, and body stature. Drug effects were measured by means of saccadic and smooth pursuit eye movements and visual analog lines obtained from the scales of Bond and Lader. There were no pharmacokinetic differences between the Japanese and white subjects. Clearance of nitrazepam was 0.91 +/- 0.165 mL/min/kg and 1.17 +/- 0.492 mL/min/kg, and half-life (t1/2) was 22.1 +/- 4.96 hours and 21.5 +/- 7.51 hours for the Japanese and European groups, respectively. Pharmacokinetic parameters showed no significant correlation with age, height, or weight. The average time-effect curves for the different parameters were comparable between groups. Compared with placebo, both groups showed similar significant reductions in average peak velocity and increases in saccadic inaccuracy and reaction time. Visual analog scores showed clear sedation in the white subjects, but insignificant effects in the Japanese subjects. Smooth pursuit did not change significantly in either group. Slope and intercept of the concentration-effect relationships for saccadic peak velocity showed considerable intersubject variability, but no clear differences between groups. The pharmacokinetics and pharmacodynamics of nitrazepam were similar in matched healthy Japanese and white subjects. Interethnic comparative studies are feasible, and provide meaningful information about potential racial differences in disposition and action of drugs. Such studies can form a rational basis for comparative clinical trials.
Assuntos
Ansiolíticos/farmacocinética , Nitrazepam/farmacocinética , Administração Oral , Adolescente , Adulto , Povo Asiático , Estudos Cross-Over , Relação Dose-Resposta a Droga , Método Duplo-Cego , Europa (Continente) , Feminino , Humanos , Japão , Masculino , Nitrazepam/farmacologia , População BrancaRESUMO
1. Endogenous fibrinolytic capacity increases after administration of 1-desamino-8-D-vasopressin. This increase is commonly attributed to an increase in release of tissue-type plasminogen activator from the endothelium. However, the possibility that 1-desamino-8-D-vasopressin influences liver blood flow, which is a major determinant of tissue-type plasminogen activator clearance, cannot be ruled out. 2. The influence of 1-desamino-8-D-vasopressin on haemodynamics, liver blood flow and fibrinolytic parameters was investigated in a randomized double-blind cross-over study in nine healthy male subjects (age 20-26 years). 3. 1-Desamino-8-D-vasopressin exerted significant haemodynamic effects: mean arterial pressure decreased maximally 12 (95% confidence interval 8-15) mmHg and heart rate increased maximally 21 (95%) confidence interval 15-27) beats/min. 4. Endogenous fibrinolytic parameters increased after administration of 1-desamino-8-D-vasopressin. Both tissue-type plasminogen activator antigen and tissue-type plasminogen activator activity were elevated and showed the maximal response shortly after drug administration was completed. 5. 1-Desamino-8-D-vasopressin increased portal venous blood flow as measured with echo-Doppler. The maximal increase in mean blood flow of 55 (95% confidence interval 19-92)% was observed at the end of the 1-desamino-8-D-vasopressin infusion and coincided with the maximal changes in systemic haemodynamics and fibrinolytic parameters. The increase in portal blood flow was not reflected in significant changes in Indocyanine Green clearance. It appears that the Indocyanine Green method is relatively insensitive to increases in liver blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Desamino Arginina Vasopressina/farmacologia , Fibrinólise/efeitos dos fármacos , Hemodinâmica/efeitos dos fármacos , Circulação Hepática/efeitos dos fármacos , Adulto , Pressão Sanguínea/efeitos dos fármacos , Método Duplo-Cego , Frequência Cardíaca/efeitos dos fármacos , Humanos , Verde de Indocianina/farmacocinética , Masculino , Veia Porta/fisiologia , Estimulação QuímicaRESUMO
1. In a previous study it was demonstrated that a decrease in liver blood flow produced a decrease in clearance of recombinant human tissue-type plasminogen activator (rt-PA). 2. The purpose of this randomized, double-blind, placebo-controlled, three-way, cross-over investigation was to determine the effect of nifedipine (20 mg orally), a compound that increases liver blood flow, on plasma concentrations of steady state endogenous and recombinant tissue-type plasminogen activator (t-PA and rt-PA) (35 mg of rt-PA over 2 h) in nine healthy male volunteers. 3. Nifedipine increased liver blood flow by 95% (42-167%) (mean (95% confidence interval)) as assessed by indocyanine green (ICG, 0.5 mg kg-1 i.v. bolus injection) clearance. 4. Nifedipine did not influence the plasma concentrations of total rt-PA antigen and activity as evaluated by the areas under the rt-PA curves from 30 min (time at which nifedipine was ingested) to 90 min during the rt-PA infusion (P > 0.05) and by analysis of a possible treatment x time interaction (P > 0.05). In addition, the plasma concentrations of endogenous t-PA remained unchanged when nifedipine was given alone. 5. In conclusion, by using nifedipine as a model compound it was demonstrated that the combination of rt-PA and a compound which increases liver blood flow probably does not lead to substantial changes in plasma concentrations of rt-PA.
Assuntos
Nifedipino/farmacologia , Ativador de Plasminogênio Tecidual/sangue , Adulto , Pressão Sanguínea/efeitos dos fármacos , Método Duplo-Cego , Interações Medicamentosas , Frequência Cardíaca/efeitos dos fármacos , Humanos , Verde de Indocianina/metabolismo , Cinética , Circulação Hepática/efeitos dos fármacos , Masculino , Proteínas Recombinantes/sangueRESUMO
Pharmacodynamic interactions of low doses of diazepam and alcohol were investigated in a double blind, randomised, 2 x 2 factorial, cross-over study in eight healthy volunteers. Alcohol or glucose 5% were administered intravenously at rates calculated to maintain breath alcohol levels of 0.5 g/l from 1.5 to 5.5 h after starting the alcohol infusion. Diazepam 5 mg or placebo were administered orally at 1.5 h. Evaluation of pharmacodynamic interactions was performed for the average results of tests performed at 2, 3.5 and 5 h. Plasma concentrations of (desmethyl-) diazepam and breath alcohol levels were measured for pharmacokinetic analysis. Breath alcohol reached pseudo steady state levels of 0.38 g/l (range: 0.24-0.57) after alcohol alone and 0.37 g/l (range: 0.27-0.52) in combination with diazepam. Alcohol effects were demonstrated for latency of saccadic eye movements, smooth pursuit eye movements and subjective drug effects. Diazepam impaired smooth pursuit and saccadic eye movements, adaptive tracking, digit symbol substitution and body sway. The effects of combined alcohol and diazepam were mostly additive without significant synergistic interactions. However, in two subjects large supra-additive effects occurred at 3.5 h following alcohol+diazepam, which were not explained by increased drug levels. The design and methods used in this study proved advantageous in evaluating low dose pharmacodynamic interactions. Despite the absence of significant synergistic interactions, unanticipated impairment of performance may occur in susceptible individuals when taking combined low doses of alcohol and diazepam.
Assuntos
Diazepam/farmacologia , Etanol/farmacologia , Adulto , Afeto/efeitos dos fármacos , Estudos Cross-Over , Diazepam/farmacocinética , Método Duplo-Cego , Interações Medicamentosas , Eletroculografia/efeitos dos fármacos , Etanol/administração & dosagem , Etanol/farmacocinética , Humanos , Injeções Intravenosas , Masculino , Equilíbrio Postural/efeitos dos fármacos , Desempenho Psicomotor/efeitos dos fármacosRESUMO
The effects of heparin (5,000 IU i.v.) and the low molecular weight heparinoid Org 10172 (Orgaran) (3,250 anti-Xa units i.v.) on components of the fibrinolytic system were studied in two double-blind, randomised, placebo-controlled, cross-over trials using healthy subjects. In study A (n = 6) the effects were studied during rest and standardized exercise and in study B (n = 6) during a low dose infusion of recombinant tissue-type plasminogen activator (rt-PA; 80 micrograms over 16 min). At rest, heparin and Org 10172 did not influence the plasma concentrations of endogenous t-PA antigen and activity, urokinase-type PA (u-PA) antigen, plasmin activatable pro-urokinase (scu-PA), active urokinase (tcu-PA) and plasminogen activator inhibitor-1 (PAI-1) antigen. Recombinant t-PA antigen and activity during rt-PA infusion were also not affected. During exercise, neither heparin nor Org 10172 influenced the area under the curve (AUC) of t-PA and u-PA antigen and t-PA activity when compared with placebo. Unexpectedly, after heparin the AUC of t-PA activity was 49% larger (range +19 to +245%) than after Org 10172 (p < 0.05). The last difference was considered spurious, scu-PA, tcu-PA and PAI-1 antigen levels at 2 min after termination of exercise were unaffected by both compounds (p > 0.05). Sulphated polysaccharides do not increase fibrinolytic activity of the plasma by changing the concentrations of the components of the fibrinolytic system.
Assuntos
Sulfatos de Condroitina , Dermatan Sulfato , Fibrinólise/efeitos dos fármacos , Glicosaminoglicanos/farmacologia , Heparina/farmacologia , Heparinoides/farmacologia , Heparitina Sulfato , Adulto , Método Duplo-Cego , Exercício Físico/fisiologia , Fibrinólise/fisiologia , Fibrinolíticos/farmacologia , Humanos , Masculino , Inibidor 1 de Ativador de Plasminogênio/sangue , Proteínas Recombinantes , Ativador de Plasminogênio Tecidual/sangue , Ativador de Plasminogênio Tipo Uroquinase/sangueRESUMO
BACKGROUND: In this study, the anticoagulant response of 12,500 IU heparin s.c. was investigated in patients with myocardial infarction and healthy volunteers to determine variabilities in response and modifying factors. METHODS AND RESULTS: On the fourth day after thrombolytic therapy, blood samples were taken before and at frequent intervals until 10 hours after the injection of 12,500 IU heparin s.c. Plasma anti-Xa activity, anti-IIa activity, and the activated partial thromboplastin time (APTT) were measured in addition to body weight and thickness of the abdominal subcutaneous fat layer. Contrary to expectations, the increase of anti-Xa activity, anti-IIa activity, and APTT compared with baseline (predrug) levels was very small, with an average maximal APTT of 42.6 seconds (SD, 12.4 seconds; range, 30.4-70.7 seconds). Subsequently, the influence of the length of the injection needle on the anticoagulant effect of 12,500 IU heparin s.c. was studied in 10 healthy volunteers to find a factor that could be responsible for the poor response in the patients. The length of the injection needle did not influence the anticoagulant effect of heparin. Large interindividual and intraindividual variabilities were seen in the volunteers. The majority of volunteers had minimal prolongation of the APTT, but very strong prolongation was also seen (maximal APTT, 163 seconds). There was no correlation between the abdominal skinfold thickness and anti-Xa activity, anti-IIa activity, or APTT (p > 0.05), but in the patient study, there was a correlation between weight and anti-Xa activity and anti-IIa activity (p < 0.05), and in the volunteer study, there was a correlation between weight and anti-Xa activity and APTT (p < 0.05). CONCLUSIONS: Subcutaneous administration of heparin in a fixed dose for prophylactic and therapeutic purposes may be inadequate because of the large interindividual and intraindividual variations in anticoagulant effect.
Assuntos
Heparina/administração & dosagem , Infarto do Miocárdio/sangue , Infarto do Miocárdio/tratamento farmacológico , Terapia Trombolítica , Adulto , Peso Corporal/fisiologia , Fator Xa/efeitos dos fármacos , Heparina/farmacocinética , Heparina/uso terapêutico , Humanos , Injeções Subcutâneas , Masculino , Pessoa de Meia-Idade , Agulhas , Tempo de Tromboplastina Parcial , Protrombina/efeitos dos fármacosRESUMO
Potential pharmacokinetic and pharmacodynamic interactions between two oral doses of GR32191 (40 and 80 mg), a new thromboxane antagonist, and heparin (5,000 IU bolus + 1,000 IU/h for 3 h) were studied in eighteen healthy male volunteers using two separate double-blind, randomised, placebo-controlled, cross-over studies. Mean (range) bleeding time values were 8.4 min (7.5-9.7) during heparin/placebo, 12.1 min (9.2-18.6) (GR32191/placebo) and 16.3 min (11.5-21.4) (GR32191/heparin) in the 40 mg study, while these values were 8.7 min (5.5-15.5), 16.0 min (9.3 - greater than 36.0) and 23.8 min (10.7 - greater than 36.0), respectively in the 80 mg study. Compared to screening values, the combination of 80 mg of GR32191 and heparin had a greater effect on the bleeding time than the sum of the prolongations after the separate treatments (p = 0.05). In the 40 mg study this was not the case. Pharmacokinetics of heparin (as assessed by plasma anti-Xa and antithrombin activity) and GR32191 were unaltered during co-administration of the two drugs. GR32191 did not influence the effects of heparin on APTT. Heparin slightly diminished the inhibition of collagen induced platelet aggregation by 80 mg of GR32191 and the U-46619 (thromboxane A2-mimetic) induced platelet aggregation remained unchanged. Overall fibrinolytic activity (as evaluated by the fibrin plate test) was similar during all three treatments in the study with 80 mg. The combination of 80 mg of GR32191 and heparin caused a prolongation of the bleeding time which was more than expected on the basis of their individual effects.
Assuntos
Compostos de Bifenilo/administração & dosagem , Tempo de Sangramento , Heparina/administração & dosagem , Ácidos Heptanoicos/administração & dosagem , Tromboxanos/antagonistas & inibidores , Compostos de Bifenilo/farmacocinética , Método Duplo-Cego , Interações Medicamentosas , Quimioterapia Combinada , Fibrinólise/efeitos dos fármacos , Hemostasia/efeitos dos fármacos , Heparina/farmacocinética , Ácidos Heptanoicos/farmacocinética , Humanos , MasculinoRESUMO
The influence of changes in liver blood flow on the clearance of rt-PA was studied both in healthy subjects and in a perfused rat liver model. Liver blood flow in healthy subjects was documented indirectly by the clearance of indocyanine green (ICG). Exercise reduced liver blood flow on average by 57% with a 95% confidence interval (95% CI) ranging from 51% to 62% (n = 5) and increased plasma levels of rt-PA activity (after an i.v. infusion of 18 mg of rt-PA over 120 min) by 119% (95% CI, 58%-203%) and rt-PA antigen by 91% (95% CI, 30%-140%). In the perfused rat liver model it was shown that halving or doubling of the physiological flow rate of a perfusate, containing rt-PA caused a proportional change in the clearance of rt-PA, while the extraction of rt-PA by the liver remained similar. In conclusion, liver blood flow is a major determinant of the clearance of rt-PA. This may have important implications for dosage of rt-PA in patients with myocardial infarction.
Assuntos
Circulação Hepática/fisiologia , Ativador de Plasminogênio Tecidual/farmacocinética , Adulto , Animais , Exercício Físico/fisiologia , Humanos , Verde de Indocianina , Infusões Intravenosas , Masculino , Taxa de Depuração Metabólica , Perfusão , Ratos , Ratos Endogâmicos , Ativador de Plasminogênio Tecidual/administração & dosagem , Ativador de Plasminogênio Tecidual/sangueRESUMO
The absorption of high and low molecular fractions of heparin from the subcutaneous compartment was evaluated in eight healthy males. They were given an intravenous infusion of 4000 U calcium heparin in 4 hours and on another occasion a subcutaneous injection of 12,500 U calcium heparin (washout period of 1 week). Anticoagulation was monitored by anti-Xa, antithrombin activity, and activated partial thromboplastin time. To evaluate factors that might influence absorption, body weight, body fat, and abdominal skinfold thickness were recorded. There was a pronounced inter-individual variability in absorption but the absorption of the two fractions of heparin was similar. The highly variable absorption was related to the abdominal skinfold thickness, and this could have implications for therapeutic and prophylactic heparin regimens.
Assuntos
Músculos Abdominais/anatomia & histologia , Heparina/farmacocinética , Absorção , Adulto , Anticorpos/análise , Disponibilidade Biológica , Esquema de Medicação , Fator Xa/imunologia , Heparina/administração & dosagem , Heparina de Baixo Peso Molecular/administração & dosagem , Heparina de Baixo Peso Molecular/farmacocinética , Humanos , Infusões Intravenosas , Injeções Subcutâneas , Masculino , Tempo de Tromboplastina Parcial , Protrombina/imunologia , Dobras CutâneasRESUMO
The effects of single-dose (10 mg) and short-term (10 mg tid) nifedipine treatment on apparent hepatic blood flow, as assessed by indocyanine green (ICG) clearance, were studied in ten healthy male subjects. ICG was measured by both spectrophotometric and high performance liquid chromatography (HPLC) assay methods. Blood clearance of ICG and apparent hepatic blood flow were increased by 30 and 50%, respectively, after single-dose nifedipine, whereas after 4 days' treatment these values were 12 and 30%. The spectrophotometric assay significantly overestimated ICG plasma concentrations from 7 minutes onwards. Although the spectrophotometric and HPLC assay showed marked differences in calculated half-lives and volume of distribution of ICG, the ICG clearance values were similar for the two assay methods.