Use of incretin agents and risk of pancreatic cancer: a population-based cohort study.

AIM: To investigate the association between the use of incretin agents and the risk of pancreatic cancer. METHODS: A retrospective population-based cohort study, using data from the Clinical Practice Research Datalink, 2007-2012, was conducted. Patients (n = 182 428) with at least one non-insulin antidiabetic drug (NIAD) prescription and aged ≥18 years during data collection, were matched one-to-one to control patients without diabetes. Multivariable Cox proportional hazards models and a new user design were used to estimate the hazard ratio (HR) of pancreatic cancer in incretin users (n = 28 370) compared with control subjects without diabetes and other NIAD-treated patients. Time-dependent adjustments were made for age, sex, lifestyle, comorbidities and drug use. RESULTS: The mean duration of follow-up was 4.1 years for incretin users. Current NIAD use was associated with a fourfold increased risk of pancreatic cancer [HR 4.28, 95% confidence interval (CI) 3.49-5.24]. This risk was almost doubled among current incretin users as compared with control subjects. Incretin use was not associated with pancreatic cancer when compared with control subjects with diabetes (HR 1.36, 95% CI 0.94-1.96); however, the 'new user' design did show an association between incretin use and pancreatic cancer when compared with control subjects with diabetes. In both cohorts with prevalent and incident users of antidiabetic drugs, the risk of pancreatic cancer almost doubled in those who had recently initiated incretin therapy (up to seven prescriptions), whereas this elevated risk dropped to baseline levels with prolonged use. CONCLUSIONS: We found that incretin use was not associated with pancreatic cancer after adjustment for the severity of the underlying Type 2 Diabetes Mellitus (T2DM). The elevated risk of pancreatic cancer in those recently initiating incretin agents is likely to be caused by protopathic bias or other types of unknown distortion. The presence of considerable confounding by disease severity and the lack of a duration-of-use relationship do not support a causal explanation for the association between incretin agents and pancreatic cancer.

Multiple intravenous doses of paracetamol result in a predictable pharmacokinetic profile in very preterm infants.

AIM: The therapeutic options available to treat neonatal pain are limited, and one alternative for nonopioid systemic treatment is paracetamol. However, pharmacokinetic data from prolonged administration of intravenous paracetamol in neonates are limited. The aim of this study was to present pharmacokinetics after multiple dose of intravenous paracetamol in very preterm infants of <32 weeks' gestation. METHODS: Fifteen very preterm infants received five, six-hourly doses of intravenous paracetamol (7.5 mg/kg). Blood samples were taken to measure paracetamol, glutathione and hepatic function, together with urine samples for paracetamol metabolites. RESULTS: A two-compartment pharmacokinetic model gave the best fit for all individual patients and resulted in a predictable pharmacokinetic profile. The estimated pharmacokinetic population parameters were volume of distribution 0.764 ± 0.225 L/kg, elimination rate constant (ke ) 0.117 ± 0.091/h and intercompartment rate constants k12 0.607 ± 0.734/h and k21 1.105 ± 0.762/h. CONCLUSION: Our study found that multiple doses of intravenous paracetamol resulted in a predictable pharmacokinetic profile in very preterm infants. Increases in postmenstrual age and weight were associated with increased clearance. No evidence of hepatotoxicity was found.

Prevalence of potential drug-drug interactions in cancer patients treated with oral anticancer drugs.

BACKGROUND: Potential drug-drug interactions (PDDIs) in patients with cancer are common, but have not previously been quantified for oral anticancer treatment. We assessed the prevalence and seriousness of potential PDDIs among ambulatory cancer patients on oral anticancer treatment. METHODS: A search was conducted in a computer-based medication prescription system for dispensing oral anticancer drugs to outpatients in three Dutch centres. Potential drug-drug interactions were identified using electronic (Drug Interaction Fact software) and manual screening methods (peer-reviewed reports). RESULTS: In the 898 patients included in the study, 1359 PDDIs were identified in 426 patients (46%, 95% confidence interval (CI)=42-50%). In 143 patients (16%), a major PDDI was identified. The drug classes most frequently involved in a major PDDI were coumarins and opioids. The majority of cases concerned central nervous system interactions, PDDIs that can cause gastrointestinal toxicity and prolongation of QT intervals. In multivariate analysis, concomitant use of more drugs (odds ratio (OR)=1.66, 95% CI=1.54-1.78, P<0001) and genito-urinary cancer (OR=0.25, 95% CI=0.12-0.52, P<0001) were risk factors. CONCLUSION: Potential drug-drug interactions are very common among cancer patients on oral cancer therapy. Physicians and pharmacists should be more aware of these potential interactions.

Risk of fracture in patients with Parkinson's disease.

UNLABELLED: The aim of the study was to determine fracture risk in incident Parkinson's disease (PD) patients. This study showed that fracture risk assessment may be indicated among patients with PD, in particular when they have recently used selective serotonin re-uptake inhibitors or high-dose antipsychotics, or have a history of fracture, falling, low body mass index (BMI) or renal disease. INTRODUCTION: PD is a movement disorder associated with falling and detrimental effects on bone. Both are recognized risk factors for fracture. Therefore, the aim was to determine fracture risk in incident PD patients stratified by treatment, severity, duration of disease and related comorbidities. METHODS: We conducted a retrospective cohort study using the UK General Practice Research Database (1987-2011). Each PD patient was matched by age, sex, calendar time and practice to a control patient without history of PD. RESULTS: We identified 4,687 incident PD patients. Compared to controls, a statistically significant increased risk was observed for any fracture (adjusted hazard ratio [AHR], 1.89; 95 % confidence interval [CI], 1.67-2.14), osteoporotic fracture (AHR, 1.99; 95 % CI, 1.72-2.30) and hip fracture (AHR 3.08; 95 % CI, 2.43-3.89). Fracture risk further increased with history of fracture, falling, low BMI, renal disease, antidepressant use and use of high-dose antipsychotics. CONCLUSION: This study showed that incident PD patients have a statistically significant increased risk of fracture. Therefore, fracture risk assessment may be indicated among PD patients, who, besides the general risk factors for fracture, like increasing age and female gender, have recently used selective serotonin re-uptake inhibitors or high-dose antipsychotics or have a history of fracture, falling, low BMI or renal disease.

[Conversion disorders]. / Konversionsstörungen.

Classification, diagnostic and therapeutic problems are central to the disease concept of conversion disorders, which are based on the presentation of psychosocial suffering by means of pseudoneurological symptoms without an organic cause. The nosological status in the current diagnostic and statistical manual of mental disorders (DSM-IV) and international classification of diseases (ICD-10) is disputed. Prevalence rates ranging from 0.3 % in the general population to 50 % in high risk clinical samples underline the relevance. Traumatic experiences play a major role in the pathogenesis. High rates of comorbid mental disorders, the danger to end in a chronic course, a high secondary illness gain and a somatic illness concept complicate psychotherapeutic approaches which are clearly indicated. Clinical experiences and open studies indicate that both psychodynamic as well as cognitive-behaviour therapies are effective.

Strategy for implementation and first results of advanced clinical decision support in hospital pharmacy practice.

Clinical decision support systems (CDSS) are the new generation clinical support tools that 'make it easy to do it right'. Despite promising results, these systems are not common practice, although experts agree that the necessary revolution in health care will depend on its implementation. To accelerate adoption a strategy is handed for structured development and validation of CDSS' content (clinical rules). The first results show that the proposed strategy is easily applicable for creating specific and reliable rules, generating relevant recommendations.

Pharmacotherapy of unlicensed medicines prepared and distributed by Dutch pharmacies.

INTRODUCTION AND OBJECTIVE: In the Netherlands, preparing and distributing pharmacies (PDPs) are taking over a large proportion of pharmacy preparations. PDPs prepare and distribute medicinal products to dispensing pharmacies. Many pharmacies have stopped pharmacy preparation. However, this contravenes the Dutch Medicines Act and the European Union (EU) Directive 2001/83/EC on which Dutch law is based. This is because the medicinal products of PDPs are unlicensed and PDPs do not have a manufacturing licence. METHODS: To solve the conflict with the Dutch Medicines Act, PDPs have since 2007 been authorised by the Dutch Health Care Inspectorate by means of a circular letter. This circular letter describes the qualitative conditions that must be fulfilled by PDPs. The circular letter's conditions state that PDPs must perform verifiable investigations to assess the availability, or not, of licensed pharmacotherapeutic alternatives (PA investigations) and to assess the pharmacotherapeutic rationale and the needs of the patient (PT investigations). RESULTS: Regular visits were performed by the Dutch Health Care Inspectorate to check the compliance of PDPs with the circular letter. This article describes the results of these inspections for PA and PT investigations. CONCLUSIONS: The results of the inspections show that so far almost all PDPs inspected have complied with the PA and PT conditions of the circular level at system level. However, in a substantial proportion of cases, the rationale of the pharmacy-made products is insufficient or insufficiently documented.

Inspectorate surveillance of preparing and distributing pharmacies in The Netherlands.

INTRODUCTION AND OBJECTIVE: The preparation of medicines in pharmacies is essential for accommodating the individual needs and medical conditions of patients in Europe and beyond. This article describes the state of pharmacy preparation in preparing and distributing pharmacies (PDPs) in the Netherlands. The Medicines Act in the Netherlands is based on the European Union Directive 2001/83/EC, which forbids a PDP from preparing and distributing unlicensed medicinal products to dispensing pharmacies. In order not to obstruct patient care, the Dutch Inspectorate has sent a Circular Letter on large-scale preparation to all Dutch pharmacists. This Circular describes the qualitative conditions that must be fulfilled by the PDPs. The aim of this study was to assess the overall compliance of Dutch PDPs with the conditions of the Circular. These conditions are: an absence of licensed pharmacotherapeutic alternatives, rational pharmacotherapy, a product dossier for all products and compliance with Good Manufacturing Practice (GMP). METHODS: PDPs are obliged to fulfil the conditions of the Circular. If PDPs do not fulfil these conditions, then they have to stop preparing and distributing medicinal products. A questionnaire was sent to all Dutch pharmacies to get information about the number of PDPs and the number of pharmacies served by each PDP. The instrument that was used in this observational study to assess the compliance of the PDPs with all conditions of the Circular is described. RESULTS: The results of the inspections until now show that on 1 November 2014, 18 out of 21 PDPs fulfilled the four conditions of the Circular. Only minor deficiencies were found with 3 out of 21 PDPs. Twenty out of the 21 PDPs visited fulfilled the condition concerning the absence of pharmacotherapeutic alternatives and 19 out of 21 PDPs visited complied with the condition of rational pharmacotherapy. Nineteen out of the 21 PDPs visited fulfilled the Circular condition that a product dossier was available for all products. All of the 21 PDPs visited complied with GMP. Regular visits, at least every 3 years, were performed by the Inspectorate to check the compliance of the PDPs with the Circular. The publication of the inspection reports on the website of the Inspectorate allowed, probably, many PDPs to be better prepared. The inspection visits showed that the PDPs have invested in compliance with the conditions of the Circular. CONCLUSIONS: Most of the PDPs fulfilled the requirements of the Circular. The Inspectorate is in consultation with the Ministry of Health, Welfare and Sport about how to proceed with the question of PDPs and the conditions they have to fulfil. Recent European case law will have to be taken into account.

Impact of the Council of Europe Resolution on quality and safety assurance requirements for medicinal products prepared in pharmacies for the special needs of patients.

INTRODUCTION AND OBJECTIVE: The regulation of pharmacy preparations, especially for standards for quality assurance and safety, is not harmonised across Europe and falls under the national competencies of individual states. There are concerns about quality control and safety for the medicinal products made in pharmacies, which is widespread in European countries. There are, however, good reasons to continue this practice, which is able to tailor preparations to the specific needs of a particular patient or patient group and to provide a supplementary source of supply when an industrially manufactured product, which is authorised for marketing is not available or when there are temporary shortages of licensed medicines. In seeking to provide guidelines for legislation and acting on the advice of an expert group dealing in pharmaceutical practices, the Committee of Ministers of the Council of Europe passed a resolution in 2011. The Council of Europe Resolution provides authorities and pharmacists with the means to reinforce safety measures for medicinal products prepared in pharmacies and to harmonise quality assurance and safety standards. It dealt with aspects of pharmacy preparation such as quality standards for preparation and distribution, marketing authorisation, product dossiers, labelling, reporting, and safety. In 2013 and 2014 the Committee of Experts carried out a survey to evaluate the impact of the resolution within a cross section of member states. The objectives of this study were both to monitor the extent to which the recommendations had been enshrined in national legislation and also to understand current differences in legislation and practice between the member states. METHODS: In the resolution of 2011 the member states were recommended to adapt their legislation in line with its provisions. The survey that was carried out in 2013 and 2014 followed the recommendations in the resolution. A questionnaire was made and sent to a cross section of member states. RESULTS: Among the member states involved, the results of this survey show a clear commitment to implement the recommendations of the resolution. CONCLUSIONS: This report presents the results of the survey with a discussion of outstanding issues.

Legislation on the preparation of medicinal products in European pharmacies and the Council of Europe Resolution.

INTRODUCTION: The rights of patients should be sufficiently protected even when an appropriate authorised medicine does not exist or is unavailable on the market. The Resolution, which was adopted by the Committee of Ministers of the Council of Europe in 2011, aims at harmonising quality and safety standards for pharmacy preparation of medicinal products in Europe. TWO PILLARS OF EU REGULATION AND THE EXCEPTIONS TO THEM: The system of regulation of medicinal products is built upon two pillars: the marketing authorisation of the medicinal product and the licence for manufacturing and wholesale. This article provides insight into the recent interpretation of the European Court of Justice concerning the scope of European Union (EU) regulation of medicinal products and the circumstances in which the EU regulation does not apply: pharmacy preparations, specialties and the compassionate use of medicines, including manufacturing licence. EU REGULATION AND THE RESOLUTION CONCERNING PHARMACY PREPARATION: Pharmacy preparations are allowed under certain strict conditions according to EU regulations. However, pharmacies specialised in preparation and distributing medicinal products to local pharmacies do not fulfil these strict conditions in EU regulation. Apart from the legal context, relevant standards for safety and quality assurance are needed in Europe in order to protect patients' rights and to avoid risks from pharmacy preparations. DISCUSSION AND CONCLUSIONS: The Council of Europe Resolution provides a means of establishing standards for safety and quality assurance for pharmacy preparations through Good Manufacturing Practice Guidelines. The Resolution is available to authorities and pharmacists in order to prevent incidents with medicines prepared in pharmacies which may threaten patients' safety. The authors conclude that pharmacy practices have changed over time in Europe and this may imply a reason for a reform of EU regulation on medicinal products.

Treatment of cefuroxime-induced neurotoxicity with continuous venovenous haemofiltration.

A 61-year-old woman with decreased consciousness, myoclonus, tremors, nystagmus and bradypnoea, due to cefuroxime-induced neurotoxicity, was admitted to the intensive care unit. Continuous venovenous haemofiltration (CVVH) rapidly reduced plasma cefuroxime concentrations and improved neurological manifestations within the next few hours. Retrospective pharmacokinetic assessment showed a total cefuroxime clearance of 166 ml/min during the CVVH.

The association between insulin use and volumetric bone mineral density, bone micro-architecture and bone strength of the distal radius in patients with type 2 diabetes - The Maastricht study.

Type 2 diabetes mellitus (T2DM) has been associated with an increased risk of fractures, despite normal to increased bone mineral density (BMD). Insulin use is one of the factors linked to this increased fracture risk. However, direct negative effects of insulin on bone quality are not expected since insulin is thought to be anabolic to bone. In this cross-sectional study the association between insulin use and volumetric BMD (vBMD), bone micro-architecture and bone strength of the distal radius, as measured with HR-pQCT, was examined. Data from 50 participants with T2DM of The Maastricht Study (mean age 62±7.5years, 44% women) was used. Participants were classified as insulin user (n=13) or non-insulin user (n=37) based on prescription data. Linear regression analysis was used to estimate the association between current insulin use and HR-pQCT derived parameters. After adjustment for age, sex, body mass index, glycated hemoglobin A1c and T2DM duration, insulin use was associated with lower total vBMD (standardized beta (ß):-0.56 (95% CI:-0.89 to -0.24)), trabecular vBMD (ß:-0.58 (95% CI:-0.87 to -0.30)), trabecular thickness (ß:-0.55 (95% CI:-0.87 to -0.23)), cortical thickness (ß:-0.41 (95% CI:-0.74 to -0.08)), log cortical pore volume (ß:-0.43 (95% CI:-0.73 to -0.13)), bone stiffness (ß:-0.39 (95% CI:-0.62 to -0.17)) and failure load (ß:-0.39 (95% CI:-0.60 to -0.17)) when compared to the non-insulin users. Insulin use was not associated with cortical vBMD, trabecular number, trabecular separation, cortical porosity and cortical pore diameter. This study indicates that insulin use is negatively associated with bone density, bone micro-architectural and bone strength parameters. These findings may partly explain the previously observed increased fracture risk in insulin users, although there may be residual confounding by other factors related to disease severity in insulin users.

Aseptic preparation of parenteral medicinal products in healthcare establishments in Europe.

In many cases, parenteral medicines with a marketing authorisation cannot be administered directly to patients, that is, they are not presented in ready-to-administer form. Before administration to patients, these medicines have to be reconstituted. Reconstitution has a special position; it can neither be seen as industrial manufacture nor as 'regular' pharmacy preparation. There are other processes in healthcare establishments (eg, parenteral nutrition), related to the reconstitution process, where the requirements of national quality assurance standards for the safe preparation of sterile products are equally important and have to be fulfilled. In European healthcare establishments, aseptic preparation of parenteral medicinal products is considered to be a process of crucial importance for patient safety because errors in the preparation of these medicines may lead to a product that can cause immediate damage to patients. Aseptic preparation of medicinal products is carried out in hospital pharmacies as well as in clinical areas in healthcare establishments. The Committee of Experts on Quality and Safety Standards for Pharmaceutical Practices and Pharmaceutical Care (Council of Europe; hereafter: Committee of Experts), supported by the European Directorate for the Quality of Medicines & Healthcare, is undertaking work on the topic of aseptic preparation of medicines. The work is carried out in cooperation with the European Association of Hospital Pharmacists on the basis of a Resolution CM/Res AP(2011)1 on Quality and Safety Assurance requirements for Medicinal Products prepared in Pharmacies for the Special Needs of Patients, which was adopted by the Committee of Ministers on 19 January 2011. The Resolution includes some recommendations and an outlook to further work on reconstitution of parenteral medicines. A survey that was sent to the different European countries demonstrated that there is no or just limited regulation concerning reconstitution in Europe. This article describes the risks associated with poor reconstitution practices and the previous work as well as the ongoing activities concerning reconstitution at the European level. The article emphasises the need for regulation in this area, which is missing at present. It is expected that consensus can be reached on a guidance document for reconstitution at the European level.

Pharmacokinetic variability of zidovudine in HIV-infected individuals: subgroup analysis and drug interactions.

OBJECTIVE: To investigate determinants of inter- and intraindividual variability of zidovudine (ZDV) pharmacokinetics in HIV-infected patients. DESIGN: A prospective study in a general 525-bed hospital with special funding for treatment and research of HIV-infected patients. METHODS: Serial blood samples were collected from 68 HIV-infected individuals providing a total of 95 pharmacokinetic curves. ZDV was measured with high-performance liquid chromatography and radioimmunoassay. Pharmacokinetic parameters were calculated by non-compartmental analysis. Patient characteristics were investigated by multivariate analysis for an influence on ZDV pharmacokinetics. RESULTS: Apparent ZDV clearance was significantly lower in patients with a lower body weight, in women, and in patients with a more advanced stage of HIV disease. Co-administration of methadone with ZDV resulted in higher plasma concentrations of ZDV, while rifampin and ganciclovir increased apparent ZDV clearance. Age, the duration of ZDV use, CD4+ cell count, creatinine clearance, elevated serum liver enzyme levels, and the use of 11 other co-administered medications were not independently related to apparent ZDV clearance. CONCLUSIONS: The pharmacokinetic profile of ZDV in several subpopulations has been evaluated, as well as the observation of possible drug-drug interactions between ZDV and 14 different drugs or groups of drugs. These data suggest that patient-individualized antiretroviral therapy may be appropriate once pharmacokinetic-pharmacodynamic relationships have been established.

An interaction between cytostatic and anticonvulsant drugs.

A young woman with epilepsy had tonic-clonic seizures during antineoplastic therapy with adriamycin and cisplatin. During two courses of cytostatic drug administration peak and trough plasma levels of phenytoin, carbamazepine, and valproate sodium were measured. Lower plasma levels of carbamazepine and valproate sodium were observed after 2 days of antineoplastic therapy. Normal plasma levels of these drugs were found 2 to 3 days after the last cisplatin dose. Impaired absorption or accelerated elimination might explain these results. Phenytoin levels were reduced to 37% of the original values, although the drug was given intravenously. Changed Michaelis-Menten parameters suggest that cisplatin increases the metabolic rate of phenytoin. Another explanation for the decreased drug levels might be an increased volume of distribution. Calculation of this volume from peak and trough levels showed an increase of the volume of distribution during and after chemotherapy.

Association of polymorphism in the cytochrome CYP2D6 and the efficacy and tolerability of simvastatin.

OBJECTIVE: Because clinical data about the therapeutic consequences of polymorphic oxidation of simvastatin by CYP2D6 have not been well reported, we sought to investigate the possible link between polymorphism of CYP2D6 and the efficacy and tolerability of simvastatin treatment in a group of 88 patients with hypercholesterolemia. METHODS: The CYP2D6 genotype was determined with use of polymerase chain reaction and restriction fragment analysis, whereas the CYP2D6 phenotype was determined by monitoring the dextromethorphan metabolism. RESULTS: Four of 5 patients with 2 defective CYP2D6 alleles discontinued the therapy at a low daily dose because of adverse events, with a significant mean decrease in the cholesterol levels of 0.23 mmol/L per milligram of simvastatin in the daily dose. In the group of 28 patients with 1 mutated CYP2D6 gene, 13 did not tolerate the therapy, whereas a mean decrease in the cholesterol levels of 0.20 mmol/L per milligram of simvastatin was found. One patient with a multiplication of the CYP2D6 gene showed a cholesterol reduction of only 0.01 mmol/L per milligram of simvastatin, at a maximal daily dose of 40 mg. Only 9 patients of the group of 54 persons who were homozygous for the wild-type allele discontinued the therapy because of intolerance. In that group, a mean decrease of cholesterol of 0.10 mmol/L per milligram of simvastatin was observed. CONCLUSIONS: Our data provide evidence that the cholesterol-lowering effect of simvastatin is influenced by CYP2D6 polymorphism. The clinical use of this knowledge may allow for more efficient individual therapies.

Intranasal apomorphine in parkinsonian on-off fluctuations.

The efficacy of intranasal apomorphine was assessed in seven patients with Parkinson's disease and severe levodopa (L-dopa)-related "off-period" disabilities. All patients responded favorably to treatment with intranasal apomorphine. The speed and the quality of motor response and the pharmacokinetic profile showed results similar to those seen after subcutaneous injection of apomorphine administered by insulin pen syringe. The simplicity in the technique of intranasal apomorphine administration was found to be superior by all patients.

Pharmacokinetic-pharmacodynamic relationships of apomorphine in patients with Parkinson's disease.

In the treatment of patients with Parkinson's disease, apomorphine has an established place as a back-up therapy if other antiparkinsonian drugs, such as levodopa and oral dopamine agonists, have not controlled the existing response fluctuations. Apomorphine is a synthetic derivative of morphine, with a totally distinct pharmacological profile. It is a very lipophilic compound which is easily (auto)oxidised. This (auto)oxidation is the main metabolic route besides glucuronidation and sulphation, which are both responsible for about 10% of the metabolic transformation. Apomorphine quickly passes the nasal and intestinal mucosa as well as the blood-brain barrier (depending on the administration route). Many routes of administration have been explored, but subcutaneous, sublingual, nasal and rectal administration are used in clinical practice. The volume of distribution varies between 1 and 2 times bodyweight. The elimination half-life is very short (30 to 90 min) depending on the type of parenteral administration. Apomorphine is a high clearance drug (3 to 5 L/kg/h) and is mainly excreted and metabolised by the liver. Only 3 to 4% is excreted unchanged in the urine. The clinical effect of apomorphine can be linked directly to its concentration in the cerebrospinal fluid. Consequently, a 2-compartment model can be used to predict the clinical effects of apomorphine. The pharmacokinetic-pharmacodynamic data reflect the clinical observations of steep dose-effect curves if apomorphine is used in patients with random 'on-off' fluctuations. These dose-effect curves are less steep in stable or 'wearing-off' (end-of-dose deterioration) patients. Intravenous infusions of apomorphine in combination with timed motor assessments can be used clinically to characterise the therapeutic window of a particular patient if dyskinesia persists after single injections of apomorphine. If more population data become available, the population pharmacokinetics-pharmacodynamics of apomorphine could be helpful in predicting the clinical effects of apomorphine in the several subgroups of patients with Parkinson's disease.

Hepatic uptake and biliary excretion of organic cations--I. Characterization of three new model compounds.

Three quaternary ammonium compounds (QACs) with different lipophilicity, triethylmethyl ammonium iodide (TEMA), tripropylmethyl ammonium iodide (TPMA) and tri-n-butylmethyl ammonium iodide (TBuMA) were given as a bolus injection of 10 mumole and 1 mumole in an isolated perfused liver. TPMA and TBuMA exhibited saturation kinetics at a dose of 10 mumole, but not when 1 mumole of the agents was given. Biliary clearance of TEMA was equal to the bile flow (0.010 ml/min), whereas for TPMA and TBuMA much higher values of 0.8 ml/min and 2.2 ml/min were found respectively. Partition coefficients of TEMA, TPMA and TBuMA between n-octanol and Krebsbicarbonate solution were 0.0013, 0.013 and 0.14 respectively. Liver-to-plasma concentration ratios were 4, 16 and 30 in the post-distribution phase, whereas bile-to-liver ratios were calculated to be 0.1, 1.3 and 14 respectively. The latter parameter varied roughly proportionally to the lipophilicity of the compounds. The liver/plasma concentration ratios corrected for intracellular binding exceeded a value of 12 indicating that accumulation in the liver of these agents cannot soley be explained by passive equilibration according to the membrane potential. Transport from liver into the bile of TPMA and TBuMA presumably also occurred against an electrochemical gradient. It was inferred that the small molecular weight compounds such as TEMA, can be transported from plasma into bile paracellularly by a passive process. Rapid uptake into the liver of such compounds may not lead to an appreciable biliary output and can even reduce the rate of biliary excretion. QACs with intermediate or high lipophilicity are transported by carrier mediated processes both at the level of hepatocyte uptake and bile canalicular transport. The influence of choleresis on hepato-biliary transport of the three QACs was investigated by giving sodium taurocholate (Tc) by constant infusion of 60 mumole/hr, increasing bile flow from 9 to 16 microliter/min. The biliary output of TEMA appeared to be basically unaffected, whereas the biliary excretion of TPMA and TBuMA was clearly elevated when the bile flow was increased. The stimulatory influence of taurocholate on the biliary output of the latter organic cations is explained by an increased net uptake of these agents into the liver and an increased net canalicular transport. This effect is proposed to be due to a reduced reabsorption from the biliary tree as a consequence of the higher bile flow and/or biliary micelle binding. Taurocholate increased liver-to-plasma ratios.(ABSTRACT TRUNCATED AT 400 WORDS)

Hepatic uptake and biliary excretion of organic cations--II. The influence of ion pair formation.

The influence of an anorganic anion iodide (I-) and an organic anion tetraphenylborate (TPB-) on the hepatic uptake and biliary excretion of three organic cations, triethylmethyl ammonium (TEMA), tripropylmethyl ammonium (TPMA) and tri-n-butylmethyl ammonium (TBuMA) was studied. The compounds were injected as a bolus (D = 1 mumole) and studied in isolated perfused livers. In the perfusion medium 25% of the amount of NaCl (3 mmole) was replaced by NaI, whereas in two other experiments TPB- was added to the medium in two concentrations (2 microM and 200 microM). NaI did not affect the biliary output of the three quaternary ammonium compounds (QACs) although an increased net rate of hepatic uptake was found for all compounds, most likely due to a decreased liver to plasma transport. Liver to plasma concentration ratios were increased, while the ratios between bile to liver and bile to plasma were not affected. TPB- in catalytic amounts added to the medium (2 microM) decreased the biliary output of TEMA and TBuMA, whereas the kinetic profile of TPMA was unchanged. The decreased biliary excretion rate of TEMA was explained by a decreased plasma level (due to the increased liver uptake) assuming that the small molecular weight compounds can enter the bile directly from plasma via the junctional complexes between the cells. The bile to plasma (B/P) ratio was not affected. In contrast, the bile to plasma (B/P) ratio and the bile to liver (B/L) ratio of TBuMA were decreased, compared with the control, probably due to an increased reabsorption from the bile, whereas the back transport from the liver into the plasma was also decreased. A large amount of TPB- (200 microM), added to the perfusion medium, dramatically changed the kinetic profile of the three QACs. Ion pair formation between the QACs and TPB- was supposed to be responsible for this effect. Plasma levels dropped more rapidly as a result of an increased rate of liver uptake. The biliary excretion of all compounds was greatly reduced (the excretion rates were 0.022, 0.19 and 0.18 nmole/min, compared with 0.047, 0.71 and 7.5 nmole/min for the controls). It is concluded that ion pair formation may play a role in the hepatobiliary transport. The rate of liver uptake of the QACs is enhanced in the presence of an anion, which is due to an increase in plasma to liver transport (k12) and a reduced liver to plasma transport (k21).(ABSTRACT TRUNCATED AT 400 WORDS)