How well does the questionnaire for identifying children with chronic conditions identify individual children who have chronic conditions?

BACKGROUND

The Questionnaire for Identifying Children With Chronic Conditions (QuICCC) is an instrument based on a conceptual noncategorical definition that uses parental responses to identify children with chronic conditions for epidemiological purposes.

OBJECTIVES

To determine whether the QuICCC is sufficiently valid, sensitive, and specific to be used to identify individual children as having a chronic condition or disability; whether parents are accurate enough that their answers to QuICCC items can be accepted as valid; and what kinds of errors in classification occur when the QuICCC is used to identify children with chronic conditions.

METHODS

The sample consisted of 424 children who were patients of 9 physicians in separate practice settings throughout New England. Each physician was briefly trained in the conceptual definition on which the QuICCC is based and then was asked to identify 25 children in his or her practice who met the definition and 25 children who did not meet the definition. The QuICCC was administered to the parents of these children by blinded interviewers via telephone. The QuICCC classification was compared with physician categorization. Discrepant cases were then followed up by asking physicians and parents to answer the original questions a second time.

RESULTS

Complete data were available on 379 (89.4%) of 424 children. There was agreement on 89% (kappa = 0.78). The sensitivity was 94%; specificity, 83%; positive predictive value, 86%; and negative predictive value, 92%. Of the 42 discordant cases, 30 parent reports on the QuICCC qualified the child as having a chronic condition when the physician classified the child as being without such a condition. Fewer (n = 12) discrepancies occurred because physicians identified children with chronic conditions that the QuICCC failed to identify. When the questions were readministered at follow-up, physicians corrected errors in rating in 9 cases; mothers changed their answers in 5 instances. In 13 instances the issues were known to both parties and appeared to arise in the "gray zone" or boundary area, where there was disagreement over whether a particular child qualified using the theoretical definition. For 11 children identified as having a chronic condition only by the parent's responses to the QuICCC, physician report appeared to be inaccurate primarily due to the physician's lack of information. In 3 cases where the physician reported the child to have a chronic condition, but the parent did not, the physician appeared to be correct. Follow-up data were incomplete on 1 child.

CONCLUSIONS

These data support the validity of parent-generated information for the evaluation of health status. Although these findings should be replicated, this study suggests that the QuICCC may be applicable also as a screening tool for individual child identification, provided that several sources of error are considered.

The new St. Jude Medical regent mechanical heart valve: laboratory measurements of hydrodynamic performance

BACKGROUND AND AIM OF THE STUDY

The St. Jude Medical (SJM) mechanical heart valve was the first bileaflet valve with leaflets and orifice all fabricated from pyrolytic carbon. In 1992, a supra-annular cuff configuration, the SJM mechanical heart valve Hemodynamic Plus Series (HP), was introduced, which gave a one-size gain in orifice area over the standard valve. In a continuing effort to improve hydrodynamic performance, a new enhanced configuration of the mechanical valve - the SJM Regent valve - has been developed. The blood-contacting components of the SJM Regent valve have the same design features as those of the standard or HP valve, but the orifice lumen area has been increased, without compromising structural integrity, by a shift in the cuff-retaining orifice rims.

METHODS

Valve performance has been measured using a laboratory simulation of the left heart system. Three samples of both valve types (SJM Regent, HP) for sizes 17 mm to 27 mm, were tested at a cardiac output of 5 l/min. Supplementary steady-flow measurements were made at flow rates between 5 and 30 l/min. Pressure and flow signals were recorded and several performance parameters, including pressure gradient, effective orifice area (EOA), insufficiency (regurgitant volume as a percent of forward flow volume) and energy loss, were computed.

RESULTS

All sizes of the SJM Regent valve showed improved hydrodynamic performance compared with the HP valve. For the small sizes (17, 19, 21 mm), the pressure gradient of the SJM Regent decreased by 37%, 36% and 39%, respectively; the EOA increased by 22%, 22% and 21%; and the total transaortic energy loss decreased by 33%, 31% and 31% compared with the HP valve. The regurgitation for both valves ranged between 4% and 8% of forward flow volume over the 17-27 mm size range.

CONCLUSIONS

Hydrodynamic measurements confirm the gain of the SJM Regent valve over the HP valve that is expected based on the increased geometric orifice area. Given its basic similarity of design, but with an increased EOA as demonstrated in vitro, the SJM Regent valve is anticipated to provide an increased level of clinical benefit.

Pharmacokinetics and metabolism of sildenafil in mouse, rat, rabbit, dog and man

1. Pharmacokinetics were studied in mouse, rat, rabbit, dog and man after single intravenous and/or oral doses of sildenafil or [14C]-sildenafil (Viagra). 2. In man, absorption from the gastrointestinal tract was essentially complete. With the exception of male rat, Tmax occurred at approximately 1 h or less. Bioavailability was attenuated by pre-systemic hepatic metabolism in all species. 3. The volume of distribution was similar in rodents and humans (1-2 l/kg) but was greater in dog (5.2 l/kg), due to lower plasma protein binding (84 versus 94-96% respectively). 4. High clearance was the principal determinant of short elimination half-lives in rodents (0.4-1.3 h), whereas moderate clearance in dog and man resulted in longer half-lives (6.1 and 3.7 h respectively). Clearances were in agreement with in vitro metabolism rates by liver microsomes from the various species. 5. After single oral or intravenous doses of [14C]-sildenafil, the majority of radioactivity was excreted in the faeces of all species. No unchanged drug was detected in the excreta of man. 6. Five principal pathways of metabolism in all species were piperazine N-demethylation, pyrazole N-demethylation, loss of a two-carbon fragment from the piperazine ring (N,N'-deethylation), oxidation of the piperazine ring and aliphatic hydroxylation. Additional metabolites arose through combinations of these pathways. 7. Sildenafil was the major component detected in human plasma. Following oral doses, AUC(infinity) for the piperazine N-desmethyl and piperazine N,N'-desethyl metabolites were 55 and 27% that of parent compound respectively.

Assessing managed care for children with chronic conditions

This paper reviews opportunities to monitor managed care for children and adolescents with chronic conditions and considers how well the Health Plan Employer Data and Information Set, version 3.0 (HEDIS 3.0), assesses care for these children. We propose four steps to strengthen the applicability of HEDIS to children with chronic conditions: (1) develop methods of identifying and monitoring groups of children with chronic conditions; (2) report HEDIS indicators for these children separately from those for other children; (3) develop and implement consumer and provider surveys that elicit information specific to these populations; and (4) develop specific structure, process, and outcomes indicators for children with chronic conditions.

Automated 96-well solid phase extraction for the determination of doramectin in cattle plasma

Automated standard and sample preparation have been coupled with 96-well solid phase extraction (SPE) technology to produce a cost effective, high throughput system for the analysis of drugs in biological media. The system was originally designed using the Packard Multiprobe 104DT robotic sample processor (RSP) to improve throughput for the assay of doramectin in cattle plasma, and the assay has since been validated (0.5-100 ng ml[-1]) using the Tecan Genesis RSP 150/8. The robotic processor conducts all liquid handling procedures involved in sample extraction. These comprise preparation of calibration standards in plasma, dispensing and diluting of plasma samples and addition of internal standard. In addition, the robot primes the 96-well SPE block, applies calibration standards and samples, draws the mixtures through the 96-well SPE block, and finally washes the block ready for manual elution. The doramectin assay involves high-performance liquid chromatography (HPLC) with fluorescence detection, and requires the sample extracts to be derivatised prior to analysis. The derivatisation procedure is performed manually in situ in the polypropylene deep 96-well block into which the samples have been eluted from the SPE-block. The derivatised samples are taken directly from the deep well block and injected into the HPLC for analysis. This type of batch processing keeps sample transfer to a minimum. Automated sample preparation, in combination with the use of 96-well technology, has reduced both cost and effort required in the analysis of doramectin in cattle plasma samples, and has resulted in improved sample throughput.

Monitoring health care for children with chronic conditions in a managed care environment

OBJECTIVE

Children with chronic health conditions face special issues in their interactions with managed care. These children often require additional and more varied services than do other children. Managed care plans increasingly include these children, especially with the growth of Medicaid managed care. This article examines the special issues facing children with chronic conditions and develops strategies for monitoring their care in managed care settings.

METHODS

The project staff conducted an extensive review of the research and policy literature related to managed care and the special needs of families with children with chronic conditions. The project also reviewed current and proposed plans of federal, state, and private groups for monitoring and, working with parents and other outside groups, identified key issues to consider in developing monitoring plans.

RESULTS

The relative rarity of many childhood conditions and the complex interactions among child, family, and community over time make assessment of their care difficult. We describe these child and family characteristics, outline essential features and domains for monitoring systems, and describe population-based and plan-based monitoring systems to assess managed care for these children and their families.

CONCLUSIONS

Monitoring for children with chronic conditions in managed care arrangements will require public health agencies and health providers to define populations systematically, assess across a variety of conditions, and monitor several domains central to the health of these families.

Monitoring and evaluating managed care for children with chronic illnesses and disabilities

OBJECTIVE

Children with chronic illnesses and disabilities are increasingly enrolling in managed care arrangements. Yet, the rapid expansion of managed care has unknown consequences for children with chronic conditions and disabilities. As managed care is likely to become the predominant mode of medical practice for children with chronic health problems, information gained from a thorough assessment of existing managed care models could be helpful in indicating adjustments and modifications that could result in improved outcomes for this population. the purpose of this article is to outline a new strategy for collecting needed information on the effects of managed care on children with chronic health problems.

METHODS

We reviewed the literature on the effects of managed care on children with chronic conditions and disabilities. We identified key domains relevant to monitoring and evaluating managed care for this population.

RESULTS

Two research approaches can provide helpful information for assessing the effects of managed care on children with chronic conditions. First, a monitoring strategy could be pursued in which enrollment trends in managed care, enrollee perceptions of access and satisfaction with care, and other general indicators of outcomes would be tracked over time using inexpensive and rapid turnaround data sources. Second, an evaluative strategy could be pursued using experimental or quasiexperimental designs, in which outcomes across a variety of domains for children with chronic conditions in managed care are compared with: (a) outcomes for the same children before enrollment in managed care; or (b) outcomes for similar children remaining in traditional fee-for-service settings. Evaluation and monitoring strategies should focus on outcomes in a number of domains including: (1) access to care; (2) utilization of services; (3) quality of care; (4) satisfaction with care; (5) expenditures for care; (6) health outcomes; and (7) family impact.

CONCLUSION

Assessing outcomes that result from enrollment in managed care for children with chronic health problems presents a formidable challenge. The research strategy outlined in this article presents one approach to meeting that challenge. The monitoring and evaluation strategies described here would require commitment of additional resources on the part of government, private foundations, and/or health plans. Given the paucity of existing information and the stakes for children with chronic conditions and their families, investment of added resources in a comprehensive monitoring and evaluation strategy is essential.

Pharmacokinetics of a series of bis(methanesulphonamido-arylalkyl)amines in the beagle dog

1. The pharmacokinetics of three closely related analogues of dofetilide have been investigated in the beagle dog. These have been compared with those of dofetilide and related to physicochemical properties and structural features of the molecules. 2. Following intravenous administration, the four compounds exhibit elimination half-lives ranging from 4.6 to 19 h. This range is due to changes in both volume of distribution and plasma clearance across the series. 3. In vitro plasma protein shows a relationship to lipophilicity within this series. Protein binding increasing from 54% for dofetilide, the least lipophilic compound (log D7.4 = 0.73) to 92% for the most lipophilic analogue (log D7.4 = 2.07). There is a trend for a decrease in the volume of distribution with increased plasma protein binding. 4. Plasma clearance values range from 2.4 to 10.2 ml/min/kg and are comprised of renal and non-renal components. Renal clearance ranges fro 0.11 to 2.9 ml/min/kg and shows an inverse correlation with and lipophilicity of the compounds. Values for the renal clearance of unbound drug suggest that only the most lipophilic derivative (III), has sufficient membrane affinity to undergo tubular reabsorption. 5. Non-renal clearance of either total or free drug shows no relationship with lipophilicity. Highest values are observed for the two compounds with a methyl substituent on the tertiary amine and lowest values for the two compounds in which the tertiary amine is incorporated into a 7-membered ring. In vitro metabolism in dog liver microsomes also shows increased lability for the two N-methyl compounds. The N-desmethyl metabolite is the major product in both cases.

Design of drugs involving the concepts and theories of drug metabolism and pharmacokinetics

Drug metabolism input to the discovery process had historically been on an empirical case-by-case basis, since, detailed descriptors of the effect on pharmacokinetics of a change in structure or physicochemical property were not available. Considerable advances have been made in recent years, such that basic rules can be applied to predict the behavior of a compound in man based on physicochemistry and structure. This is particularly true in the areas of absorption, distribution, and clearance. In particular, knowledge of the reactions catalyzed by the enzymes of drug metabolism, including the cytochrome P450 super family, can be used in the design of new chemical entities, together with the usual pharmacological-derived SAR. The combination of both pharmacokinetics and pharmacodynamics at the discovery stage leads to drugs with optimum performance characteristics. Such drugs are easier to develop, representing a huge saving in resources. Moreover, the marketed compound is much more likely to find high clinical utilization. This review uses dofetilide, fluconazole, and amlodipine to highlight the multifaceted consequences of changing chemical structure, in terms of drug disposition, and reinforces these principles with examples from the literature.

Significance of metabolism in the disposition and action of the antidysrhythmic drug, dofetilide. In vitro studies and correlation with in vivo data

Dofetilide, a class III antidysrhythmic agent, undergoes both renal and metabolic clearance. Characterization of the metabolism in vitro allows explanation of species differences, whereas identification of the human enzymes involved permits assessment of potential drug interaction. In liver microsomes, the rate of oxidative metabolism of dofetilide is in the order: male rat > female rat > dog > humans, which correlates with the metabolic clearance seen in vivo. In vitro products of oxidative metabolism, formed by N-dealkylation, are the same as those formed in vivo, with the N-desmethyl being the major product. This route of dofetilide metabolism is mediated by cytochrome P450 (CYP). In humans, N-demethylation has a high KM of 657 +/- 116 microM, indicating low affinity for the enzyme's active site. In a number of human liver microsomal preparations, this rate correlated (r = 0.903) with the activity of CYP3A4. There was no correlation with the activities of other isozymes. Specific isozyme inhibitors also indicated the involvement of CYP3A4, with partial inhibition being observed with ketoconazole and troleandeomycin, whereas the activator, alpha-naphthaflavone, caused increased turnover. No inhibition was observed with specific inhibitors or competing substrates for other isozymes. Dofetilide did not significantly inhibit CYP2C9, CYP2D6, or CYP3A4 at concentrations up to 100 microM in vitro. In contrast, amiodarone (IC50, 25 microM) and flecainide (49 microM) inhibited CYP2C9 and quinidine (0.26 microM), and flecainide (0.44 microM) inhibited CYP2D6. Many antidysrhythmic drugs have active, circulating metabolites, complicating the relationship of dose and clinical response. In vitro pharmacology studies allow assessment of the potential contribution to the pharmacological profile by metabolites. Potency of dofetilide and metabolites has been compared for class III (K+ channel blockade) and class I (Na+ channel blockade) antidysrhythmic activities. Three of the metabolites of dofetilide displayed class III activity, but at concentrations at least 20-fold higher than dofetilide. Dofetilide N-oxide showed class I activity, but only at high concentration. Neither resting membrane potential or action potential amplitude were affected by any metabolite. This lack of biologically relevant activity is in accord with the close correlation between plasma concentrations of dofetilide and pharmacological response.

Effects of streptozotocin-induced diabetes and insulin treatment on substance P of the rat arterial wall

Substance P (SP) is present in perivascular nerves throughout the mammalian vasculature. Reports of diminished SP levels in nerve and gastrointestinal tissues of diabetic rats led us to examine SP-like immunoreactivity (SP-LI) in large arteries by RIA. Six weeks after inducing diabetes with streptozotocin (STZ), SP-LI was measured in the thoracic aorta, abdominal aorta, and the proximal superior mesenteric artery. In diabetics we measured a doubling (P<0.01) of SP-LI in all three artery wall preparations. This finding was verified in a second experiment which included a subset of diabetics treated daily with insulin for the sixth week of the holding period. Again, we measured a two-fold or greater increase of SP-LI (P<0.01-0.05) in arteries from the diabetics and found that insulin treatment significantly reduced SP-LI (P<0.05). In contrast to reports of diminished SP content in other tissues of diabetic rats, our findings demonstrate that the artery wall experiences at least a two-fold increase of SP-LI in the diabetic state. Furthermore, this elevation of SP-LI is reduced by insulin. We speculate that these changes of arterial wall SP-LI may contribute to altered regulation of the vascular system in the diabetic state.

The perceived long-term impact of a psychiatry clerkship on personal growth and clinical skills

The authors investigated the effects of a psychiatry clerkship that over 14 years has had a constant training philosophy and faculty and has been located in the same acute general hospital setting. In the study, 169 graduates completed a questionnaire on the effects of the clerkship on their knowledge of psychiatry, management of emotional problems in their patients, and personal development. Based on the graduates' responses, the results reveal that the clerkship indeed has had a lasting impact on its former students. Possible implications for recruitment of students into psychiatry are discussed.

Comparison of the disposition of two novel combined thromboxane synthase inhibitors/thromboxane A2 receptor antagonists in the isolated perfused rat liver

1. The pharmacokinetics of two combined thromboxane synthase inhibitor/thromboxane A2 receptor antagonists were investigated in an isolated perfused rat liver preparation. 2. The clearance of both UK 101613 (15.4 +/- 1.9 ml/min) and UK 102333 (14.9 +/- 1.6 ml/min) was limited by hepatic bloodflow. Both hepatic uptake and biliary excretion of UK 101613 appeared to be active processes. The apparent biliary clearance of UK 101613 (10.3 +/- 2.3 ml/min) was less than perfusate clearance, indicating accumulation within the hepatocytes. 3. The efficiency of the active hepatic uptake of UK 101613 and UK 102333 explains the rapid removal of these compounds from the systemic circulation. The processes of biliary and/or metabolic clearance of UK 101613 and UK 102333 appear to be subsequent to and independent of perfusate clearance. 4. Although the compounds are of similar structure and have a similar hepatic extraction (> 0.9), UK 101613 had an apparent biliary clearance approximately twice that of UK 102333. This is due to the formation of a metabolite of UK 102333 which reduces the amount of parent compound available for biliary excretion. 5. Inhibition of this latter metabolism by ketoconazole (10 microM) resulted in the two compounds having comparable apparent biliary clearances.

Overview of causes and costs of injuries in Massachusetts: a methodology for analysis of state data

Massachusetts has developed the first State profile of the causes and costs of injury based on the national study, "Cost of Injury in the United States: A Report to Congress." Incidence of fatal injuries is based on Massachusetts data; nonfatal hospitalized injuries, on Massachusetts age and sex rates and U.S. cause data; and nonhospitalized injuries, on U.S. rates applied to Massachusetts census data. Lifetime costs per injured person are based on national data adjusted for higher personal health care expenditures and for higher mean annual earnings in Massachusetts. The estimated total lifetime cost for the 1.4 million injuries that occurred in 1989 is $4.4 billion--$1.7 billion for health care and $2.7 billion for lost earnings. Injuries attributed to motor vehicles and falls account for more than half of the total cost. The other cause categories are poisonings, fire-burns, firearms, drowings-near drownings, and other. For every person who dies from an injury, 17 people are hospitalized, and an estimated 535 people require outpatient treatment, consultation, or restricted activity. Development of a State-based cost report can be useful in monitoring the contribution of injuries to health status and in planning effective injury prevention strategies in a community-based health care system. The methodology described in this paper can be replicated by other States through accessing their State-specific mortality and hospital discharge data bases.

A database obtained from in vitro function testing of mechanical heart valves

The in vitro function of the CarboMedics, Medtronic Hall, Omniscience, Starr-Edwards, St. Jude and Sorin (formerly Shiley) Monostrut heart valves have been compared using a pulsatile flow model left heart and load system. A wide range of flows and heart rates were used. The above valves in all sizes and in both aortic and mitral positions were tested. Results for transvalvular pressure, regurgitation and effective orifice area are presented. The small size St. Jude valves showed the least transvalvular pressure and largest effective orifice area. For large valves, the least regurgitation was exhibited by the Starr-Edwards valve. The data provides a reference for the range of normal performance that can be expected of mechanical prosthetic heart valves.

Importance of metabolic stability and hepatic distribution to the pharmacokinetic profile of amlodipine

1. In an isolated perfused rat liver (IPRL) model, the extensive hepatic uptake and subsequent slow redistribution of amlodipine into the perfusate have been demonstrated. The apparent liver volume for amlodipine was 920 ml compared with 38ml for nitrendipine. 2. Metabolism is the major clearance mechanism of amlodipine and nitrendipine in animals and man. In the IPRL, the intrinsic (metabolic) clearance and first-pass extraction values for amlodipine are similar to those of nitrendipine. This is in contrast with in vitro metabolic stability data in rat liver microsomes which indicate about 40-fold greater metabolic stability for amlodipine. 3. The discrepancy between relative clearance rates for the two preparations may be explained by consideration of the hepatic volume of the two compounds, with the higher liver volume of amlodipine amplifying the whole organ clearance.

Prevalence of medical technology assistance among children in Massachusetts in 1987 and 1990

In 1987 and 1990 in Massachusetts, surveys were conducted to determine the size, pattern of distribution, and trends in the population of children assisted by medical technology. The authors obtained an unduplicated count of all Massachusetts children from 3 months to 18 years of age who used one or more of the following: tracheostomy, respirator, oxygen, suctioning, gastrostomy, jejunal or nasogastric feedings, ostomies, urethral catheterization, ureteral diversion, intravenous access, or dialysis. By comparing counts obtained from medical and educational sources, the authors were able to perform a capture-recapture analysis to estimate the overall number of children dependent upon these technologies. The number of children identified in our surveys increased from 1,085 in 1987 to 1,540 in 1990. However, the capture-recapture analysis yielded estimates of 2,147 plus or minus 230 for 1987 and 2,237 plus or minus 131 for 1990. This suggests that the population of children dependent upon medical technology was essentially stable during this period, and that the 42 percent increase in the number of children identified in our survey reflected improved sampling techniques. During the 3 years, shifts in the pattern of technology use were noted, however. Use of oxygen and gastrostomy increased, and urostomy use declined. A change in the age distribution of the children was also documented, with a shift in the preponderence of technology use from 12 to 24 months in 1987 to children in the first year of life in 1990. Using the 1990 estimate and the 1990 U.S. census figures, an overall prevalence estimate of 0.16 percent was calculated. Applying this to the U.S.child population yields an estimate of 101,800 children assisted by medical technology nationwide(assuming comparable technology use in other States). This information will facilitate policy analysis and program planning on regional and national levels for this medically complex group of children.

Issues involved in the definition and classification of chronic health conditions

The need for a widely applicable definition of chronic conditions for research, policy, and program development has led to an extensive review of the development of such definitions, the considerations involved in their use, and some recommendations for a new approach. This paper examines some of the methodologic and conceptual issues related to defining and classifying chronic conditions and describes some consequences resulting from decisions made about these issues. While most examples are taken from child health applications, the basic concepts apply to all age groups. The dominant method for identifying and classifying children as having a chronic condition has relied on the presence of an individual health condition of lengthy duration. This condition-specific or "categorical" approach has increasingly seemed neither pragmatically nor conceptually sound. Thus, the development of a "generic" approach, which focuses on elements that are shared by many conditions, children, and families, is recommended. Such a definition might reflect the child's functional status or ongoing use of medical services over a specified time period. In addition, it is suggested that conditions be classified based on the experience of individual children, thus emphasizing the tremendous variability in expression of seemingly similar conditions.

Relationship among bile tolerance, bile salt deconjugation, and assimilation of cholesterol by Lactobacillus acidophilus

The relationships among growth in the presence of bile, deconjugation of sodium taurocholate, and assimilation of cholesterol by 19 cultures of Lactobacillus acidophilus were examined. Cultures of L. acidophilus were grown at 37 degrees C in lactobacilli MRS broth supplemented with sodium thioglycollate, sodium taurocholate, and cholesterol (cholesterol phosphatidyl choline micelles). Deconjugation activity was maximum in the late exponential phase of growth, which also coincided with maximum assimilation of cholesterol. Considerable variation existed among cultures in their ability to grow in the presence of bile, to deconjugate sodium taurocholate, and to assimilate cholesterol. However, statistical analyses revealed no significant correlations.

Bioanalytical data in decision making: discovery and development

1. Bioanalysis is traditionally associated with the development phase of drugs; its use in discovery programmes is often ignored but can have a major impact. 2. Pharmacokinetic studies conducted in conjunction with pharmacology screening can provide additional information to that considered in conventional structure activity relationships. Such factors as half-life and bioavailability can be critical in designing improved drugs. 3. Analytical methods in discovery programmes may differ from those used in later development work: for instance bioassay allows a common assay system for a large number of project compounds. Moreover its use, when combined with conventional methods, such as h.p.l.c., allows active metabolites to be readily detected. 4. Bioanalytical data generated in discovery and pre-clinical programmes are a valuable guide to early clinical programmes. Plasma concentration-response data from these programmes can be compared with those obtained in man. Such comparisons are particularly valuable during the phase one-initial dose escalation study. To maximize this it is our practice to generate pharmacokinetic data between each dose increase.

Pharmacokinetics and metabolism of dofetilide in mouse, rat, dog and man

1. Pharmacokinetics of dofetilide were studied in man, dog, rat and mouse after single i.v. and oral doses of dofetilide or 14C-dofetilide. 2. Dofetilide was absorbed completely in all species. Low metabolic clearance in man resulted in complete bioavailability following oral administration. Higher metabolic clearance in rodents, and to a lesser extent dogs, resulted in decreased bioavailability because of first-pass metabolism. 3. Following i.v. administration, the volume of distribution showed only moderate variation in all species (2.8-6.3 l/kg). High plasma clearance in rodents resulted in short half-life values (mouse 0.32, male rat 0.5 and female rat 1.2 h), whilst lower clearance in dog and man gave longer terminal elimination half-lives (4.6 and 7.6 h respectively). 4. After single i.v. doses of 14C-dofetilide, unchanged drug was the major component excreted in urine of all species with several metabolites also present. 5. Metabolites identified in urine from all species were formed by N-oxidation or N-dealkylation of the tertiary nitrogen atom of dofetilide. 6. After oral and i.v. administration of 14C-dofetilide to man, parent compound was the only detectable component present in plasma and represented 75% of plasma radioactivity. No single metabolite accounted for greater than 5% of plasma radioactivity.

Discrimination in vitro between the acoustic emissions from Bjork-Shiley convexo-concave valves with and without a broken minor strut

A statistical pattern recognition technique is used to learn and recognise the frequency spectra of the closing sounds emitted by Bjork-Shiley convexo-concave heart valves, with and without fractured minor struts, when operating in vitro. The sounds are generated with test valves operating under a variety of conditions in a model left ventricle. It is found in the learning stage that the discriminant functions generated correctly classified almost all of the cases within the learning set. When applied to cases outside the learning set, including a recording of a clinically implanted valve, the functions correctly classify the valves. These preliminary results, for a limited number of valves, lead us to believe that the discriminant analysis of heart valve sounds is a promising noninvasive method for screening patients with implanted Bjork-Shiley convexo-concave valves.

Liquid-liquid extraction and high-performance liquid chromatography for the determination of a novel antidysrhythmic agent (UK-68,798) in human urine

A routine method for the determination of a novel class III antidysrhythmic agent, 1-(4-methanesulphonamidophenoxy)-2-[N-(4-methanesulponamidophen ethyl)- N-methylamino]ethane, in human urine has been developed. The method involves solvent extraction followed by high-performance liquid chromatography on an unmodified silica column with ultraviolet detection. Despite a low recovery of drug through the three-stage extraction procedure a reliable assay with high precision (coefficient of variation less than 6%) and a limit of determination of 2.5 ng/ml was achieved. The method has been applied to the analysis of samples following single oral and intravenous doses of 1-12.5 micrograms/kg of the drug to human volunteers.