Analysis of traumatic intracranial hemorrhage and delayed traumatic intracranial hemorrhage in patients with isolated head injury on anticoagulation and antiplatelet therapy

Objectives

Anticoagulants and antiplatelet (ACAP) agents are increasingly and frequently used, especially in the elderly. The present study was carried out to assess the prevalence of delayed traumatic intracranial hemorrhage (dtICH) after a normal result on an initial head computed tomography (CT) in adults who were taking ACAP medication.

Materials and Methods

The present retrospective included all adult patients who arrived in the emergency department between January 2017 and January 2021 with a history of fall from the patient's own height, while being on ACAP medication with an isolated head injury. The Institutional Review Board approved the study with a waiver of consent. The primary outcome measures were prevalence of dtICH in patients who had initial normal CT scan brain and were on ACAP medication.

Results

There were 2137 patients on ACAP medication, of which 1062 were male, and 1075 were of the female gender. The mean age of the patients was 82.1 years. About 8.2% had positive first CT scans (176/2137), while 0.023 (27/1149) had dtICH. The most common positive finding on the CT scan was subarachnoid hemorrhage followed by subdural hemorrhage. Male gender positively correlated with increased risk for first CT being positive (P = 0.033). Patient's with comorbidity of cirrhosis and chemotherapy had higher risk of dtICH (P = 0.47, 0.011).

Conclusion

There was a very low (0.023%) prevalence of dtICH. Dual therapy or Coumadin therapy made up the majority of tICH. Cirrhosis and chemotherapy were associated with the risk of a repeat CT scan being positive with an initial CT scan negative.

Informatics progress of the Global Burden of Animal Diseases programme towards data for One Health

The Global Burden of Animal Diseases (GBADs) programme will provide data-driven evidence that policy-makers can use to evaluate options, inform decisions, and measure the success of animal health and welfare interventions. The GBADs' Informatics team is developing a transparent process for identifying, analysing, visualising and sharing data to calculate livestock disease burdens and drive models and dashboards. These data can be combined with data on other global burdens (human health, crop loss, foodborne diseases) to provide a comprehensive range of information on One Health, required to address such issues as antimicrobial resistance and climate change. The programme began by gathering open data from international organisations (which are undergoing their own digital transformations). Efforts to achieve an accurate estimate of livestock numbers revealed problems in finding, accessing and reconciling data from different sources over time. Ontologies and graph databases are being developed to bridge data silos and improve the findability and interoperability of data. Dashboards, data stories, a documentation website and a Data Governance Handbook explain GBADs data, now available through an application programming interface. Sharing data quality assessments builds trust in such data, encouraging their application to livestock and One Health issues. Animal welfare data present a particular challenge, as much of this information is held privately and discussions continue regarding which data are the most relevant. Accurate livestock numbers are an essential input for calculating biomass, which subsequently feeds into calculations of antimicrobial use and climate change. The GBADs data are also essential to at least eight of the United Nations Sustainable Development Goals.

Traumatic Refractory Ventricular Fibrillation Successfully Treated with Intra-Arrest Esmolol

Here, we describe a case of refractory ventricular fibrillation (RVF) in an undifferentiated trauma patient that responded to intra-arrest esmolol. To our knowledge, this is the first case of RVF in an undifferentiated trauma patient that responded to intra-arrest esmolol. This case continues to support the growing evidence for use of esmolol as a treatment of refractory fibrillation and should be considered even in undifferentiated traumatic arrest patients prior to the cessation of resuscitation efforts.

Absence of Low-Energy Shape Coexistence in ^{80}Ge: The Nonobservation of a Proposed Excited 0_{2}^{+} Level at 639 keV

The ^{80}Ge structure was investigated in a high-statistics β-decay experiment of ^{80}Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through γ, β-e, e-γ, and γ-γ spectroscopy. No evidence was found for the recently reported 0_{2}^{+} 639-keV level suggested as evidence for low-energy shape coexistence in ^{80}Ge. Large-scale shell model calculations performed in ^{78,80,82}Ge place the 0_{2}^{+} level in ^{80}Ge at 2 MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in ^{80}Ge.

A novel phosphoglucomutase-deficient mouse model reveals aberrant glycosylation and early embryonic lethality

Patients with phosphoglucomutase (PGM1) deficiency, a congenital disorder of glycosylation (CDG) suffer from multiple disease phenotypes. Midline cleft defects are present at birth. Overtime, additional clinical phenotypes, which include severe hypoglycemia, hepatopathy, growth retardation, hormonal deficiencies, hemostatic anomalies, frequently lethal, early-onset of dilated cardiomyopathy and myopathy emerge, reflecting the central roles of the enzyme in (glycogen) metabolism and glycosylation. To delineate the pathophysiology of the tissue-specific disease phenotypes, we constructed a constitutive Pgm2 (mouse ortholog of human PGM1)-knockout (KO) mouse model using CRISPR-Cas9 technology. After multiple crosses between heterozygous parents, we were unable to identify homozygous life births in 78 newborn pups (P = 1.59897E-06), suggesting an embryonic lethality phenotype in the homozygotes. Ultrasound studies of the course of pregnancy confirmed Pgm2-deficient pups succumb before E9.5. Oral galactose supplementation (9 mg/mL drinking water) did not rescue the lethality. Biochemical studies of tissues and skin fibroblasts harvested from heterozygous animals confirmed reduced Pgm2 enzyme activity and abundance, but no change in glycogen content. However, glycomics analyses in serum revealed an abnormal glycosylation pattern in the Pgm2^+/- animals, similar to that seen in PGM1-CDG.

The TGFβ pathway is a key player for the endothelial-to-hematopoietic transition in the embryonic aorta

The embryonic aorta produces hematopoietic stem and progenitor cells from a hemogenic endothelium localized in the aortic floor through an endothelial to hematopoietic transition. It has been long proposed that the Bone Morphogenetic Protein (BMP)/Transforming Growth Factor ß (TGFß) signaling pathway was implicated in aortic hematopoiesis but the very nature of the signal was unknown. Here, using thorough expression analysis of the BMP/TGFß signaling pathway members in the endothelial and hematopoietic compartments of the aorta at pre-hematopoietic and hematopoietic stages, we show that the TGFß pathway is preferentially balanced with a prominent role of Alk1/TgfßR2/Smad1 and 5 on both chicken and mouse species. Functional analysis using embryonic stem cells mutated for Acvrl1 revealed an enhanced propensity to produce hematopoietic cells. Collectively, we reveal that TGFß through the Alk1/TgfßR2 receptor axis is acting on endothelial cells to produce hematopoiesis.

Signaling events mediated by α3β1 integrin are essential for mammary tumorigenesis

The constitutive activation of β-catenin signaling in the mammary basal epithelial cell layer in transgenic K5ΔNβcat mice leads to basal-type tumor development. Integrins of the β1 family and integrin-mediated signaling events have an important role in breast tumor growth and progression. We show here that the deletion of α3β1 integrin, a major laminin receptor, from the basal layer of the mammary epithelium of K5ΔNβcat mice completely prevented the tumorigenesis induced by β-catenin signaling. Moreover, the depletion of α3β1 integrin from a spontaneously transformed mouse mammary basal epithelial cell line (MEC) prevented the cells from forming colonies in soft agar and greatly reduced tumor development in orthotopic grafts. Inhibition of the integrin signaling intermediates Rac1 or PAK1 (P21-activated Kinase 1) in MEC affected tumor cell growth in soft agar, whereas the expression of activated forms of these effectors in α3-depleted cells rescued the capacity of these cells to grow in non-adherent conditions. Similarly, the tumorigenic potential of α3-depleted cells was restored by the expression of activated PAK1, as assessed by orthotopic transplantation assay. In three-dimensional Matrigel culture, MEC survival and proliferation were affected by the depletion of α3β1 integrin, which also significantly decreased the activation of focal adhesion kinase (FAK), mitogen-activated protein kinase (MAPK) and c-Jun NH2-terminal kinase (JNK). Our data suggest that the activation of signaling cascades downstream from α3β1 and involving the Rac1/PAK1 pathway, MAPK and JNK, promotes prosurvival and proproliferative signals required for the malignant growth of basal mammary epithelial cells, providing further insight into the molecular mechanisms underlying breast cancer initiation and progression.

Biocompatibility of engineered nanoparticles for drug delivery

The rapid advancement of nanotechnology has raised the possibility of using engineered nanoparticles that interact within biological environments for treatment of diseases. Nanoparticles interacting with cells and the extracellular environment can trigger a sequence of biological effects. These effects largely depend on the dynamic physicochemical characteristics of nanoparticles, which determine the biocompatibility and efficacy of the intended outcomes. Understanding the mechanisms behind these different outcomes will allow prediction of the relationship between nanostructures and their interactions with the biological milieu. At present, almost no standard biocompatibility evaluation criteria have been established, in particular for nanoparticles used in drug delivery systems. Therefore, an appropriate safety guideline of nanoparticles on human health with assessable endpoints is needed. In this review, we discuss the data existing in the literature regarding biocompatibility of nanoparticles for drug delivery applications. We also review the various types of nanoparticles used in drug delivery systems while addressing new challenges and research directions. Presenting the aforementioned information will aid in getting one step closer to formulating compatibility criteria for biological systems under exposure to different nanoparticles.

Surgical resection of gastrointestinal stromal tumors after treatment with imatinib

BACKGROUND

Surgical resection of gastrointestinal stromal tumors (GISTs) has been the most effective therapy for these rare tumors. Imatinib has been introduced as systemic therapy for locally advanced and metastatic GIST. In this study, the surgical resection rates and long-term outcomes of patients treated with preoperative imatinib for locally advanced primary, recurrent, or metastatic GISTs were evaluated.

METHODS

Patients were retrospectively assessed for completeness of surgical resection and for disease-free and overall survival after resection.

RESULTS

Forty-six patients underwent surgery after treatment with imatinib. Eleven were treated for locally advanced primary GISTs for a median of 11.9 months, followed by complete surgical resection. All eleven were alive at a median of 19.5 months, and ten were free of disease. Thirty-five patients were treated for recurrent or metastatic GIST. Of these, eleven underwent complete resection. Six of the eleven patients had recurrent disease at a median of 15.1 months. All eleven patients were alive at a median of 30.7 months. Patients with a partial radiographic tumor response to imatinib had significantly higher complete resection rates than patients with progressive disease (91% vs. 4%; P < .001). Of the 24 patients with incomplete resection, 18 initially responded to imatinib but were unable to undergo complete resection after they progressed before surgery.

CONCLUSIONS

Preoperative imatinib can decrease tumor volume and is associated with complete surgical resection in locally advanced primary GISTs. Early surgical intervention should be considered for imatinib-responsive recurrent or metastatic GIST, since complete resection is rarely achieved once tumor progression occurs.

The value of plasma citrulline to predict mucosal injury in intestinal allografts

Diagnosis of intestinal transplant rejection depends on clinical assessment, endoscopy and most importantly, histology of intestinal biopsies. Plasma citrulline levels (P-Cit) reflect functional enterocyte mass in nontransplant patients and have been evaluated in two small series after transplant. This study was designed to determine the sensitivity and specificity of P-Cit as diagnostic tool for allograft injury, especially to distinguish between viral enteritis and rejection. We prospectively collected 403 P-Cit samples within 24 h of intestinal biopsy in 49 patients. P-Cit levels were correlated with the mucosal damage and histopathological diagnoses. P-Cit levels in bowels with significant mucosal damage (i.e. moderate or severe rejection, viral enteritis, PTLD, ischemia reperfusion injury, allergic enteritis) were significantly lower than in intestines with no or mild injury (i.e. indeterminate or mild rejection, nonspecific enteritis): 22.9 +/- 15.4 versus 38 +/- 23.2 nmol/mL (p < 0.0001). Sensitivity and specificity of the test were 80% and 58.1% for rejection, and 56.5% and 66% for viral enteritis, thereby unable to distinguish between both entities. In conclusion, P-Cit reflects the extent of mucosal injury regardless of the etiology, but does not seem to be a predictive marker for rejection or viral enteritis, as its values may decline only when diffuse mucosal damage has occurred.

Outcome of postradiation osteosarcoma does not correlate with chemotherapy response

Postradiation osteosarcoma is a rare tumor with a historically poor prognosis. Recent reports concerning the prognosis of the disease have been conflicting. We ascertained the long-term outcome of patients with this disease treated in the era of contemporary chemotherapy. Twenty-seven patients diagnosed with postradiation osteosarcoma and treated with chemotherapy and surgical resection from 1980-2003 were identified. Demographics, anatomic location, stage, chemo- therapy, necrosis rate, recurrence and metastatic rates were recorded; Kaplan-Meier survival rates were estimated. The median age was 54 years (range, 12-86 years). Nineteen patients were female and eight patients were male. Median followup was 39.2 months (range, 0-218 months). Twenty-two patients received induction chemotherapy for a mean of four cycles (range, 2-6 cycles). Mean tumor necrosis was 63.5%. Seven patients had 90% necrosis; four of these patients died of their disease. The mean survival was 23 months, and the 5-year disease free survival estimate was 27.2%. Histologic response to chemotherapy did not correlate with survival. Patients who had a latency of greater than 10 years after radiation had a better prognosis. Unlike conventional osteosarcoma, response to chemotherapy (necrosis) did not have prognostic significance. Current chemotherapy regimens fail to impact survival in postradiation osteosarcoma.

LEVEL OF EVIDENCE

Therapeutic study, level IV (retrospective comparative study).

Biochemical and molecular diagnosis of lipoamide dehydrogenase deficiency in a North American Ashkenazi Jewish family

A late-onset presentation of lipoamide dehydrogenase (E3) deficiency is described in a North American Ashkenazi Jewish (AJ) family. Diagnosis was made by urine organic acid and molecular analyses.

Chondrosarcoma of the scapula

BACKGROUND

Chondrosarcoma is the second most common primary sarcoma of bone. It often develops within flat bones, such as the pelvis, ribs, and scapula. In the current study, the authors reviewed the surgical experience and long-term oncologic outcomes of patients with chondrosarcoma arising in the scapula.

METHODS

The medical records of 29 consecutive patients with chondrosarcoma of the scapula were reviewed. The patients were treated between 1954 and 1994. All patients had localized disease at the time of presentation. The tumors were classified histologically as Grade 1 (10 patients), Grade 2 (10 patients), Grade 3 (7 patients), dedifferentiated (1 patient), and mesenchymal (1 patient) (using the criteria of Evans et al.). The mean maximal dimension of the tumors was 11 cm. Twenty-five patients underwent limb-sparing surgical resection and 4 patients underwent forequarter amputations. The median follow-up was 13 years (range, 1-35 years).

RESULTS

At last follow-up, 22 patients (76%) were free of disease and 7 patients (24%) had died of their disease. Local recurrence occurred in 4 patients at 7 months, 16 months, 40 months, and 43 months, respectively. The local recurrence-free survival rate was 86% at 5 years, 10 years, and 20 years. Disease-specific survival was 83% at 5 years, 74% at 10 years, and 74% at 20 years. Patients who had low-grade chondrosarcomas had better survival compared with patients who had high-grade chondrosarcomas (P = 0.07).

CONCLUSIONS

Patients who had localized chondrosarcoma of the scapula had a favorable long-term outcome, most likely due to the unique anatomic features that improved the likelihood of achieving wide surgical margins with limb-sparing surgery, despite the frequent presentation of locally advanced disease.

Single and multiple metachronous osteosarcoma tumors after therapy

BACKGROUND

The objective of the current study was to determine the incidence, clinical and pathologic characteristics, and outcome of patients with conventional osteosarcoma who developed metachronous tumors after treatment for the primary tumor and prevention of pulmonary metastases.

METHODS

The medical records of 270 pediatric patients (younger than age 18 years) were reviewed. The prevention and absence of pulmonary metastases was confirmed by chest radiographs and computerized scans of the lungs. Radionuclide bone scans were used to confirm the absence of skeletal metastases.

RESULTS

Eleven patients with metachronous tumors were identified. Index primary tumors involved the femur (n = 8), the tibia (n = 2), and the radius (n = 1). Single metachronous tumors developed in the femur (n = 6), in the humerus (n = 1), and multifocal in multiple bones (n = 4). Two patients later developed second metachronous tumors. The interval between identification of the primary tumor to development of the single metachronous tumors varied from 11 months to 78 months and from 12 months to 42 months for synchronous multifocal tumors. Metachronous tumors were treated with single-agent cisplatin or ifosfamide. Only 1 patient experienced > 90% tumor necrosis. Pulmonary metastases were not detected in 10 of 11 patients at the time metachronous tumors were discovered. In the 11th patient, synchronous pulmonary metastasis with the metachronous tumor was noted. Three patients had a prior history of bilateral retinoblastoma. The Li-Fraumeni syndrome may have been present in another patient. Six patients died. Five patients have survived for 20+ to 50+ months after the appearance, treatment, and resection of metachronous tumors.

CONCLUSIONS

With improvement in the cure rate, metachronous osteosarcoma should be recognized as an important sequela in long-term survivors. The etiology of this disease is unknown. Speculation rests on a skeletal multicentric origin, which includes an inherited predisposition to develop osteosarcoma in retinoblastoma and in the Li-Fraumeni syndrome. Meticulous follow-up is required to permit early detection and successful therapeutic intervention.

Can cure in patients with osteosarcoma be achieved exclusively with chemotherapy and abrogation of surgery?

BACKGROUND

Contemporary therapy for osteosarcoma is comprised of initial treatment with chemotherapy and surgical extirpation of the primary tumor in the affected bone. In view of the major advances forged by chemotherapy in the treatment of the primary tumor, an attempt was made to destroy the tumor exclusively with this therapeutic modality and abrogate surgery.

METHODS

Thirty-one consecutive patients were treated. All had localized disease (absence of metastases) at the time of diagnosis. Initial treatment with chemotherapy was comprised of high-dose methotrexate and leucovorin rescue (MTX-LF) in 3 patients and intraarterial cisplatin in 28 patients. Clinical, radiologic, angiographic, radionuclide, and histologic investigations were utilized to assess the efficacy of treatment. After a response at 3 months, entry into the study was permitted and treatment was maintained for a total of 18-21 months with a combination of agents comprised of MTX-LF, intraarterial cisplatin, and doxorubicin. Patients were monitored closely for disease recurrence with the investigations outlined earlier. Two informed consents were required: one at the time of diagnosis and another at 3 months after the initial response had been attained.

RESULTS

Only 3 of 31 patients were cured with the administration of chemotherapy alone. Local recurrence and pulmonary metastases were not reported to develop in these 3 patients during a follow-up period of 204+ to 225+ months. Four other patients also possibly were cured with chemotherapy alone. At their request, several months after the cessation of chemotherapy, they underwent surgical extirpation of the tumor. No evidence of viable tumor was found. These patients remained free of disease for 192+ to 216+ months. Thus, only seven patients did not develop local recurrence and/or pulmonary metastases. Among the remaining 24 patients, 9 developed local recurrences without pulmonary metastases 14-74 months (median, 30 months) after the initial response. Eight of the nine patients were rendered tumor free by extirpation of the local recurrence. Two of these eight patients subsequently died, one of the acquired immunodeficiency syndrome (AIDS) and the other of varicella septicemia. The ninth patient refused amputation and died of metabolic complications. Three other patients developed local recurrences 20-69 months and pulmonary metastases 10-98 months after achievement of the initial response. These patients were rendered tumor free by extirpation of the local recurrence and metastasectomy. One of these patients also later died of AIDS. In the remaining 12 patients, local recurrences developed 5-29 months (median, 14 months) after the initial response was achieved. The patients also developed pulmonary metastases 11-60 months after the initial response. In eight patients the local recurrences were extirpated and metastasectomy was performed; however, these patients later died of recurrent pulmonary metastases. The remaining four patients refused to undergo extirpation of the local recurrence. The pulmonary metastases were not resected. They failed to respond to alternate therapy. Thus, the tumor-free survival rate was 23% (7 of 31 patients): 3 patients who were treated with chemotherapy only and 4 patients who were treated with chemotherapy plus surgery. The overall survival rate (patients who remained free of disease and those who underwent resection for local recurrence and metastasectomy) was 48% (15 of 31 patients). Prior to the deaths from AIDS and varicella septicemia, the overall survival was 58% (18 of 31 patients).

CONCLUSIONS

Utilizing the regimen employed in the current study, only 3 of 31 patients with osteosarcoma (10%) were cured exclusively with chemotherapy. Four additional patients who underwent extirpation of the primary tumor without disease recurrence and in whom no viable tumor was found in the resected specimens possibly could increase the number of patients who potentially were cured with chemotherapy to 7 (23%). With an overall expected cure rate of 50-65% with "conventional" sin whom no viable tumor was found in the resected specimens possibly could increase the number of patients who potentially were cured with chemotherapy to 7 (23%). With an overall expected cure rate of 50-65% with "conventional" strategies, the results of the current study do not justify the adoption of current forms of chemotherapy as exclusive treatments for osteosarcoma.

The Rac GTPase-activating protein RotundRacGAP interferes with Drac1 and Dcdc42 signalling in Drosophila melanogaster

RhoGTPases are negatively regulated by GTPase-activating proteins (GAPs). Here we demonstrate that Drosophila RotundRacGAP is active in vitro on Drac1 and Dcdc42 but not Drho1. Similarly, in yeast, RotundRacGAP interacts specifically with Drac1 and Dcdc42, as well as with their activated V12 forms, showing a particularly strong interaction with Dcdc42V12. In the fly, lowering RotundRacGAP dosage specifically modifies eye defects induced by expressing Drac1 or Dcdc42 but not Drho1, confirming that Drac1 and Dcdc42 are indeed in vivo targets of RotundRacGAP. Furthermore, embryonic-directed expression of either RotundRacGAP, or dominant negative Drac1N17, transgenes induces similar defects in dorsal closure and inhibits Drac1-dependent cytoskeleton assembly at the leading edge. Expression of truncated forms of RotundRacGAP shows that the GAP domain of RotundRacGAP is essential for its function. Unexpectedly, transgenes encoding Drac1N17, Dcdc42N17, or RotundRacGAP do not affect the c-Jun N-terminal kinase-dependent gene expression of decapentaplegic and puckered, indicating that another Drac1-independent signal redundantly activates this pathway. Finally, in a situation where Drac1 is constitutively activated, RotundRacGAP greatly reduces the ectopic expression of decapentaplegic, possibly by negatively regulating Dcdc42.

RotundRacGAP functions with Ras during spermatogenesis and retinal differentiation in Drosophila melanogaster

Our analysis of rotund (rn) null mutations in Drosophila melanogaster revealed that deletion of the rn locus affects both spermatid and retinal differentiation. In the male reproductive system, the absence of RnRacGAP induced small testes, empty seminal vesicles, short testicular cysts, reduced amounts of interspermatid membrane, the absence of individualization complexes, and incomplete mitochondrial condensation. Flagellar growth continued within the short rn null cysts to produce large bulbous terminations of intertwined mature flagella. Organization of the retina was also severely perturbed as evidenced by grossly misshapen ommatidia containing reduced numbers of photoreceptor and pigment cells. These morphological phenotypes were rescued by genomic rnRacGAP transgenes, demonstrating that RnRacGAP function is critical to spermatid and retinal differentiation. The testicular phenotypes were suppressed by heterozygous hypomorphic mutations in the Dras1 and drk genes, indicating cross talk between RacGAP-regulated signaling and that of the Ras pathway. The observed genetic interactions are consistent with a model in which Rac signaling is activated by Ras and negatively regulated by RnRacGAP during spermatid differentiation. RnRacGAP and Ras cross talk also operated during retinal differentiation; however, while the heterozygous hypomorphic drk mutation continued to act as a suppressor of the rn null mutation, the heterozygous hypomorphic Dras1 mutation induced novel retinal phenotypes.

Beta-blockade in heart failure: a comparison of carvedilol with metoprolol

OBJECTIVES

This study was performed to compare the long-term clinical efficacy of treatment with metoprolol versus carvedilol in patients with chronic heart failure.

BACKGROUND

Beta-adrenergic blockade is of proven value in chronic heart failure. Metoprolol, a selective beta-blocker, is widely used, but recent trials suggest carvedilol, a nonselective beta-blocker with alpha-1-receptor antagonist activity and antioxidant activities, is also effective. It is uncertain, however, if these additional properties of carvedilol provide further clinical benefit compared with metoprolol.

METHODS

In this randomized double-blind control trial, 51 patients with chronic heart failure and mean left ventricular (LV) ejection fraction of 26% +/- 1.8% were randomly assigned treatment with metoprolol 50 mg twice daily or carvedilol 25 mg twice daily in addition to standard therapy after a four-week dose titration period for a total of 12 weeks. Response was assessed by a quality of life questionnaire, New York Heart Association class, exercise capacity (6-min walk test), radionucleotide ventriculography for LV ejection fraction, two-dimensional echocardiography measurement of LV dimensions and diastolic filling and 24-h electrocardiograph monitoring to assess heart rate variability.

RESULTS

Both carvedilol and metoprolol produced highly significant improvement in symptoms (p < 0.001), exercise capacity (p < 0.05) and LV ejection fraction (p < 0.001), and there were no significant differences between the two drugs. Carvedilol had a significantly greater effect on sitting and standing blood pressure, LV end-diastolic dimension and normalized the mitral E wave deceleration time.

CONCLUSIONS

Both metoprolol and carvedilol were equally effective in improving symptoms, quality of life, exercise capacity and LV ejection fraction, although carvedilol lowers blood pressure more than metoprolol.

Netilmicin pharmacokinetics in Hong Kong Chinese cancer patients

OBJECTIVES

To study the pharmacokinetics of netilmicin in Chinese haematology-oncology patients and to determine the pharmacokinetic differences, if any, between this patient subpopulation of Chinese and Caucasians.

METHODS

A prospective study was carried out in the adult oncology unit of a major hospital in Hong Kong. During a 6 week period in 1997, all patients commencing on netilmicin therapy were monitored; the patients' demographics, clinical status, netilmicin dose and regimen, and drug administration/blood sampling time were collected. Pharmacokinetic parameters were generated using the USC*PACK package based on specifics of the patients themselves and Caucasians matched for the same patients' parameters using the Bayesian alogrithms.

RESULTS

A total of 22 patients were enrolled into the study. Twenty-nine sets of levels were drawn, but only 25 sets from 18 patients (86%) were interpretable. The predicted peak (7.47+/-1.46 microg ml-1 ) and trough levels (1.39+/-0.96 microg ml-1 ) generated by USC*PACK were found to be significantly higher than the levels observed (6.01+/-1.14 microg ml-1 and 0.93+/-0.71 microg ml-1, respectively). Netilmicin clearance, volume of distribution and rate of elimination were all significantly higher in this Chinese subpopulation than those predicted for matched Caucasians. Conclusion Alterations in the netilmicin pharmacokinetics observed in our study population might be related to the disease state and/or ethics of the study patient population. Direct application of Caucasian based population pharmacokinetic parameters to this subgroup of Chinese patients may not be appropriate and may result in underdose.

Topiramate and metabolic acidosis

Topiramate (TPM) is a novel antiepileptic medication (AED) with at least three mechanisms of action. A possible fourth mechanism, that of a carbonic anhydrase inhibitor, also may contribute to its antiepileptic properties. We report a patient with intractable epilepsy and normal renal function who developed a normal anion gap metabolic acidosis, which worsened during elective surgery for temporal lobectomy. We believe this side effect of TPM can become clinically significant during surgery, concomitant use of another carbonic anhydrase inhibitor, and potentially with the ketogenic diet.

Sudden and unexpected neonatal death: a protocol for the postmortem diagnosis of fatty acid oxidation disorders

Fatty acid oxidation (FAO) disorders are frequently reported as the cause of sudden and unexpected death, but their postmortem identification remains difficult. Over a period of 5 years, the authors have identified 44 cases representing five FAO disorders and 19 additional cases without a diagnosis of a specific defect. Among the two groups, 13 patients died in the neonatal period, 10 in the FAO group, and three from the undetermined defect group. This outcome was consistently associated with exclusive breast feeding and presumably poor caloric intake. The diagnosis of FAO disorder in these cases was based on the analysis of postmortem liver and bile. In postmortem liver, informative findings are microvesicular steatosis, elevated fatty acid concentrations, glucose depletion, and low carnitine concentration. Bile carnitine analysis and acylcarnitine profiling have expanded significantly the effectiveness of the initial protocol and could lead, based on preliminary observations, to better identification of patients who may have been missed or left undetermined by the analysis of liver only. If an autopsy is not performed, informative findings can still be obtained by analysis of blood spots collected for newborn screenings and by biochemical testing of parents and asymptomatic siblings.

Searching interaction partners of protein kinase CK2beta subunit by two-hybrid screening

To date, the intracellular regulation of protein kinase CK2 is unknown. However it was observed that the enzyme associates with several intracellular proteins and the formation of such molecular complexes may represent a mechanism for the control of CK2 activity. Using the Interaction Trap system in yeast, with the CK2beta as a bait, we looked for CK2 partners. We present the identification of new potential partners of CK2beta and it is hoped that their classification will help in understanding the physiological roles and the regulation of CK2 in the cell.

Clinical and biochemical features of fatty acid oxidation disorders

Inborn errors of fatty acid oxidation (FAO) represent a group of metabolic disorders that has brought forward many interesting developments, as highlighted by the rapid pace of discovery of new defects and by the recognition of an ever-increasing spectrum of clinical phenotypes. This review includes a clinical and biochemical summary of the FAO disorders known to date, a synopsis of four recently discovered defects (short-chain 3-hydroxy acyl-CoA [coenzyme A] dehydrogenase deficiency, medium-chain 3-ketoacyl-CoA thiolase deficiency, 3-hydroxy-3-methylglutaryl-CoA synthase deficiency, and long-chain fatty acid transport deficiency) and of two susceptibility variations in the short-chain acyl-CoA dehydrogenase gene, and guidelines for the biochemical work-up of candidate patients.

Use of indapamide in hospital and community clinics and its effect on plasma potassium in Chinese patients

OBJECTIVES

To investigate the usage pattern of indapamide and other antihypertensive drugs in patients attending a community-based government outpatient clinic (GOPC) or a hospital-based specialist clinic (SC). The plasma potassium concentrations of patients receiving indapamide and other diuretics were also examined.

METHOD

Prescriptions from the SC and the GOPC were reviewed and collected during January 1998. Patients' plasma potassium concentrations and the date of initiation of each medication were retrieved from the hospital computer databases at SC. An age- and sex-matched control group of patients on non-diuretic antihypertensive drugs was identified.

RESULTS

A total of 1648 and 773 prescriptions were collected from the SC during a 1-week period and GOPC during a 1-month period, respectively. Approximately half (45%) of the patients received antihypertensive treatment. Indapamide was five times more frequently prescribed in GOPC than SC (84.7 vs. 17.7%, P<0.001). Calcium channel blocking agents were the commonest antihypertensive drugs used in both clinics. The mean plasma potassium concentration of patients taking indapamide was lower than that of the control group (P = 0.037). Multiple linear regression analysis showed that consumption of indapamide (P =0.002) and duration of diuretic therapy (P = 0.023) were significantly related to changes in plasma potassium concentrations [multiple regression equation for potassium level = 4.09-0.145 (thiazide = 1)-0.377 (indapamide = 1) -0.00468 (duration of diuretic therapy in months)].

CONCLUSION

Indapamide was used extensively in the community clinic and less in the hospital-based outpatient clinic. Patients receiving indapamide had a significantly lower plasma potassium concentration as compared to other diuretics or antihypertensive groups and this was predicted by a multiple linear regression model. Monitoring plasma electrolytes before initiation of indapamide treatment and at regular intervals thereafter is essential for detecting the hypokalaemia that may occur in Chinese patients.

Beta blockers in heart failure: a comparison of a vasodilating beta blocker with metoprolol

OBJECTIVE

To determine whether a third generation vasodilating beta blocker (celiprolol) has long term clinical advantages over metoprolol in patients with chronic heart failure.

DESIGN

A double blind placebo controlled randomised trial.

SETTING

University teaching Hospital.

PATIENTS

50 patients with stable chronic heart failure (NYHA class II-IV) due to idiopathic dilated, ischaemic, or hypertensive cardiomyopathy, with left ventricular ejection fraction < 0.45.

INTERVENTIONS

Celiprolol 200 mg daily (n = 21), metoprolol 50 mg twice daily (n = 19), or placebo (n = 10) for three months with a four week dose titration period. After the double blind period, patients entered an open label study (with placebo group receiving beta blockers) and were assessed after one year.

MAIN OUTCOME MEASURES

Clinical response, efficacy, and tolerance were assessed by the Minnesota heart failure symptom questionnaire six minute walk test, Doppler echocardiography (systolic and diastolic function), radionuclide ventriculography, and atrial and brain natriuretic peptides measured at baseline and after three months.

RESULTS

In the metoprolol group at 12 weeks v baseline there was a 47% reduction in symptom score (p < 0.001), improvement of NYHA class (mean (SEM), 2.6 (0.12) to 1.9 (0.13), p = 0.001), exercise distance (1246 (54) to 1402 (52) feet, p < 0.001), and left ventricular ejection fraction (26.9(3.1)% to 31(3.0)%, p = 0.016), and a fall in heart rate (resting, 79 (3) to 62 (3) beats/min, p < 0.001). In the celiprolol group there was a 38% reduction in symptom score (p = 0.02), less improvement in exercise distance (1191 (55) to 1256 (61) feet, p = 0.05), and no significant changes in NYHA class, left ventricular ejection fraction, or heart rate. Mortality at one year was 11% in metoprolol and 19% in the celiprolol group, and symptomatic improvement was maintained in the survivors.

CONCLUSIONS

Both drugs were well tolerated but the vasodilator properties of celiprolol do not seem to provide any obvious additional benefit in the long term treatment of heart failure.

Overview of the hospital formulary systems in Hong Kong. Princess Margaret Hospital as a baseline

OBJECTIVE

To investigate the popularity of formulary systems in all Hong Kong hospitals and to compare these with the newly introduced formulary system in a major government hospital, the Princess Margaret Hospital (PMH), as the baseline.

DESIGN

Questionnaire and selected interviews by pharmacy students.

SETTING

All hospital pharmacies in Hong Kong.

PARTICIPANTS

Department managers (directors of pharmacy services) of hospital pharmacies.

MAIN OUTCOME MEASURE

The popularity of the hospitals' formulary systems and their formulary decision-making strategies. Calculations of cost savings of the new formulary system in PMH and a comparison of the PMH system with the US standards were also made.

RESULTS

Among 38 responding hospitals, 35 (92%) had a formulary handbook and 21 (55.3%) claimed to have a formulary system. The evaluation processes and formulary decision-making procedures were found to be inadequate because basic components in drug evaluation (e.g., standardized criteria for drug evaluation) were not used regularly. However, the formulary system in PMH was found to be comparable with the US standards. Substantial cost savings were made through rejection of less cost-effective drugs by the Formulary Subcommittee in PMH.

CONCLUSIONS

In general, comprehensive formulary systems are still not popular in Hong Kong. This may be due to insufficient staffing and lack of administrative and physicians' support. The new formulary system in PMH can be used as a model to develop a successful formulary system in which hospital pharmacists can prove their expertise for the benefit of both hospitals and patients in Hong Kong.

Antibiotic exposure and its relationship to postantibiotic effect and bactericidal activity: constant versus exponentially decreasing tobramycin concentrations against Pseudomonas aeruginosa

In vitro postantibiotic effects (PAEs) exhibited by a standard strain of Pseudomonas aeruginosa following exposure to tobramycin at constant concentrations were compared to those at exponentially decreasing concentrations. Exposure to a constant concentration showed more extensive bacterial killing and resulted in longer PAEs at comparable areas under the concentration-time curves above the MIC. This phenomenon suggests a significant contribution of pharmacokinetics to antimicrobial pharmacodynamics.

Efficient assay for the determination of atenolol in human plasma and urine by high-performance liquid chromatography with fluorescence detection

An efficient method for the determination of atenolol in human plasma and urine was developed and validated. alpha-Hydroxymetoprolol, a compound with a similar polarity to atenolol, was used as the internal standard in the present high-performance liquid chromatographic analysis with fluorescence detection. The assay was validated for the concentration range of 2 to 5000 ng/ml in plasma and 1 to 20 microg/ml in urine. For both plasma and urine, the lower limit of detection was 1 ng/ml. The intra-day and inter-day variabilities for plasma samples at 40 and 900 ng/ml, and urine samples at 9.5 microg/ml were <3% (n=5).

Mathematical evaluation of the influence of adverse effect on therapeutic efficacy in a direct response system: a case of pharmacodynamic variability of adverse effect

Two major concerns in therapeutics are the efficacy (E) and adverse effects (Ae) exhibited by a pharmacological agent. Although these elements are studied routinely in both animals and humans during the drug development processes, the data are usually considered independently and in different contexts. Since E and Ae are different yet inseparable components in drug therapy, E should not be used as the sole descriptor for drug responses. To accommodate the influence of Ae on E, the present approach requires the observed Ae data to be transformed to the equivalencies of E data (Ae'). Using appropriate pharmacokinetic modeling techniques, this approach permits the prediction of the adjusted therapeutic effect (ATE) (i.e. , E minus Ae') as a function of time. Effects of pharmacodynamic variability of Ae due to variations in Hill's parameters (i.e., Ae (max), AeC (50), and n (Ae) ) on ATE were studied by computer simulations for a hypothetical one-compartment model drug that displays simple first-order absorption and elimination with central sites for E and Ae. An increase in Ae' (max) and a decrease in AeC (50) and n (Ae) cause a downward shift and peak inversion on the ATE versus time curves coupling with a longer duration of influence of Ae on E. Results also showed that the downward shift of these curves was more apparent with decreasing n (Ae) values and that peak inversion became less noticeable for n (Ae) values <1.5. Subsequent analyses established the optimal dose for the hypothetical drug studied. This approach allows a more comprehensive description of the time course of the overall drug responses and is potentially useful for therapeutic drug monitoring and dose selection during the drug development process.

Validated assay for the determination of celiprolol in plasma using high-performance liquid chromatography and a silanol deactivated reversed-phase support

Previously reported methods for the determination of celiprolol in plasma could not be satisfactorily employed due to interference from plasma components. Thus, an improved, convenient and efficient method for the determination of the plasma concentration of celiprolol was developed using a simple solvent extraction step followed by high-performance liquid chromatography on a silanol deactivated C18 column with fluorescence detection. The plasma interference was resolved from celiprolol and the typical trailing of basic compounds on reversed-phase HPLC was eliminated. The peak-area ratio versus plasma concentration was linear over the range of 5-1000 ng/ml and the detection limit was 5 ng/ml.

Effect of low dose beta blockers on atrial and ventricular (B type) natriuretic factor in heart failure: a double blind, randomised comparison of metoprolol and a third generation vasodilating beta blocker

OBJECTIVES

This study examines the acute effects of two differing beta adrenergic blocking agents (metoprolol and a third generation vasodilating beta blocker) on plasma concentrations of atrial natriuretic factor (ANF), brain (ventricular) natriuretic factor (BNF), and haemodynamic variables in patients with heart failure.

SETTING

University teaching hospital.

METHODS

20 patients with impaired left ventricular systolic function [ejection fraction 32 (SEM 2.3)%] were randomised in a double blind manner to receive either oral metoprolol 6.25 mg twice daily or celiprolol 25 mg daily. Haemodynamic variables were evaluated by Swan-Ganz pulmonary artery catheter over 24 hours. ANF and BNF concentrations were measured at baseline, 5 h, and 24 h by radioimmunoassay.

RESULTS

At baseline ANF and BNF concentrations were considerably raised compared to the normal range. Treatment with metoprolol caused ANF to rise further to 147% of the basal level at 5 h (P = 0.017) and 112% at 24 h (P = 0.029). This was associated with a small but non-significant rise in pulmonary capillary wedge pressure. Cardiac output and systemic vascular resistance were unchanged at 24 h. In contrast, after celiprolol ANF fell to 90% of basal levels at 5 h and to 74% of basal level at 24 h (P = 0.019), associated with a small but non-significant fall in pulmonary capillary wedge pressure [-3.3 (2.7) mm Hg] and systemic vascular resistance, and rise in cardiac output from 3.2 (0.2) to 4.0 (0.4) l/min (P = 0.04). BNF concentrations rose to 112% of baseline at 5 h (P = 0.09) after metoprolol but fell slightly, to 91% of baseline values, after celiprolol (NS).

CONCLUSIONS

Metoprolol, even in very low doses (6.25 mg), produced a rise in ANF and BNF, although minimal haemodynamic changes were detected. In contrast, a vasodilating beta blocker was associated with a significant fall in ANF and BNF and a small rise in cardiac output. This study confirms both the advantages of vasodilating beta blockers over metoprolol for initial treatment of heart failure and the usefulness of ANF and BNF measurements for the assessment of drug effects in heart failure compared to traditional haemodynamic measurements.

Pharmacists' attitudes toward adverse drug reaction reporting in Hong Kong

OBJECTIVE

To study the attitudes and knowledge of pharmacists in Hong Kong toward the reporting of adverse drug reactions (ADRs).

METHODS

In December 1993, all pharmacists who were working in retail shops (n = 230), hospitals (n = 44), or outpatient clinics (n = 12) in Hong Kong were sent a questionnaire as well as a letter explaining the purpose of the survey.

RESULTS

One hundred and twenty-nine pharmacists (retail pharmacies 40.4 percent, hospitals 68.2 percent, outpatient clinics 50 percent) responded. Although 93 percent of the pharmacists in this survey agreed that it is necessary to report ADRs, a much smaller proportion (14.7 percent) had actually done so in the previous 12 months. Most pharmacists (87.4 percent) were not aware of any ADR reporting system in Hong Kong. There did not appear to be a relationship between ADR reporting and the length or place of practice, workload, or patient contact time. Severe or unusual ADRs and ADRs to new products were perceived to be significant enough to report.

CONCLUSIONS

The great majority of pharmacists in Hong Kong agreed on the necessity of reporting ADRs. The lack of knowledge of an ADR reporting program might have led to nonreporting in the past. It is important that there be continuing efforts to promote ADR reporting programs.

The effect of infection with Schistosoma margrebowiei on the growth of Bulinus natalensis

Three age groups of Bulinus natalensis, immature, mature but not yet egg-laying and mature egg-laying, were infected with miracidia of Schistosoma margrebowiei. The growth of infected, exposed but showing no signs of infection, and uninfected control groups, were examined at weekly intervals for ten weeks post exposure. Snails exposed to infection when immature, even in the group where no patent development ensued, showed a statistically significant reduction in growth and this was evident as early as 2-5 weeks post exposure. When infection occurred at the stage prior to egg-laying a significant reduction in growth was seen but only in the group which developed a patent infection. This was also the case for the egg-laying group although the reduction in growth was only significant in the final three weeks of the experiment. Thus in all three age groups, growth rate was reduced and the infected snails were significantly smaller at the end of ten weeks compared with the controls. The reasons for these effects are discussed.

Analysis of clinical experience with a new twist lock connectology

The DextroLyte II (Dex II) Peritoneal Dialysis System was designed to improve safety and convenience in dialysis therapy. Connectors introduced with this system have a threaded recessed male connector with a corresponding female counterpart. Products are provided for CAPD, Single Use Y, Long Life Y and CCPD. Safety and convenience features intended to reduce peritonitis rates and improve patient acceptance include the following: 1. Connectors with threaded male and corresponding female counterparts which provide a dual seal 2. Easy-to-break frangible which seals the solution bag until ready for use 3. A flange on the connector ensures proper hand placement by providing a safety shield to prevent contamination during connection 4. A hinged shield containing an impregnated povidone-iodine sponge easily snaps around the bag connector 5. A Quick Disconnect Clamp (QDC) provides external occlusion permitting safe disconnection for bagless techniques without opening the system 6. A standard medication port provides easy access for administration of intraperitoneal medication Results of a multicenter study performed in nine centers are as follows: Total patient participants 121 Total patient months 1207 Overall peritonitis rate 1 episode in 43 patient months We conclude that the Dex II peritoneal dialysis systems provide safe dialysis therapy as evidenced by the exceptional peritonitis rates. Patient acceptance has been excellent due to the inclusion of the safety and convenience features described.

Clinical experience and comparative analysis of the standard and fast peritoneal equilibration tests (PET)

The fast peritoneal equilibration test (PET) has been proposed as a substitute procedure for the standard PET because it is less expensive and less time consuming since fewer samples must be drawn. This study was undertaken to compare the fast and standard PETs to determine if the fast PET is a viable alternative. Fifteen patients participated in the study. Results from the standard PETs indicate 13 patients had average permeability and 2 patients had high transport. Corresponding fast PETs indicate 10 patients with average permeability, 2 patients with high transport, 1 patient had discrepancies between the D/P ratios and drain volume, and 2 patients were noncompliant and did not complete the fast PET. We conclude that the fast PET is a valid screening tool to evaluate peritoneal membrane permeability in patients who have previously undergone a standard PET. It is cost effective and timesaving. The test is easily invalidated if patients fail to comply with instructions for the test. The fast PET is primarily useful as a screening device to determine whether permeability has changed.

The daily cercarial emission rhythm of Schistosoma margrebowiei with particular reference to dark period stimuli

The cercariae of Schistosoma margrebowiei showed two peaks of emergence from Bulinus natalensis in a 12 h light/dark cycle. Peak emission occurred at 0700 h (one hour after the onset of light) and at 1900 h (one hour after the onset of darkness). Both peaks were of equal magnitude and were maintained during constant illumination indicating that the rhythm is innate. Delaying or advancing the timing of the dark period did not affect the timing of these two peaks. Following a five minute dark treatment elevation in cercarial output resulted irrespective of when the treatment was applied. Subjecting snails to various intensities of light only resulted in an elevation in output when a sudden change in intensity from 0 to 360 Lux or the reverse was applied. No response was seen to a gradual change in light intensity although the parasite could detect a change in light from 1 to 0 Lux. These responses appear to optimize the chances of host parasite contact.

Single-dose and steady-state pharmacokinetics of doxazosin given in combination with chlorothiazide to hypertensive subjects

The pharmacokinetics of doxazosin were determined in hypertensive subjects after a single dose of 1 mg, and at steady-state while receiving doses of 1, 2, 4 and 8 mg of the drug daily. Chlorothiazide 500 mg once daily was administered as additional therapy throughout the study. After a single dose doxazosin was rapidly absorbed, with peak plasma drug concentrations (Cmax) occurring after 2.1 +/- 0.4 hours. The elimination half-life in plasma was 10.7 +/- 1.2 hours. These parameters remained essentially unchanged during maintenance administration of doxazosin at each of the dose levels. Calculations of Cmax and area under the concentration-time curve (AUC0----infinity) indicated that the pharmacokinetic disposition of the drug remained linear over the dose range 1 to 8 mg.

Pathologic fracture in osteosarcoma. Impact of chemotherapy on primary tumor and survival

Twenty patients with osteosarcoma and pathologic fractures were treated with a chemotherapeutic regimen consisting of cis-diamminedichloroplatinum-II (CDP), Adriamycin (ADR) (doxorubicin) and high-dose methotrexate with citrovorum factor "rescue" (MTX-CF). Before the introduction of the regimen, the primary tumor in two patients was treated by immediate amputation and in 13 with preoperative intra-arterial CDP. Among these 13 patients, responses (healing) were observed in 11 (one required the addition of radiation therapy). In three patients, the responses were so dramatic that, at their request, surgery was deferred and treatment exclusively with chemotherapy was instituted. Based on this experience, treatment exclusively with chemotherapy was also administered to an additional five patients who were admitted without pathologic fractures. In the course of such treatment, pathologic fractures also developed; notwithstanding, chemotherapy was maintained and healing also occurred. One of the 20 patients had pulmonary metastases at diagnosis; these were resected after treatment and pathologic examination revealed no evidence of viable tumor. The remaining 19 patients were free of pulmonary metastases but these later developed in seven patients. These data were compared to a historical control series in which 16 of 21 patients with pathologic fractures developed pulmonary metastases. Three of the chemotherapy treated patients died of nonosteosarcoma related causes (leukemia, generalized varicella, and a metabolic complication). Overall, survival was improved in the chemotherapy treated patients as compared to the historical control series: 10 of 20 versus 6 of 21, respectively. Pathologic fractures in osteosarcoma may heal under treatment with chemotherapy, which also has a favorable impact on the eradication of pulmonary metastases and survival.

Influence of intravenous infusion duration on the tissue drug concentration profile

The influence of intravenous infusion duration of a single dose of drug on the time course of drug concentration in the peripheral compartment of the classical two-compartment pharmacokinetic model was studied by computer simulation. The aim was to illustrate the general relationships among infusion duration T, dose, minimum effective concentration MEC at the effector (tissue) site, maximum tissue drug concentration C2,max, and the duration of effective tissue concentrations tD,tiss for those drugs where there is an equilibration delay between concentration at the effector site and plasma. Simulations of C2,max vs. T for meperidine, sulfamethoxazole, ampicillin, and metronidazole showed that, although maximum plasma concentration may decrease markedly with increasing T, C2,max decreased only slightly with increasing T. Simulations of the influence of T on the duration of effective plasma concentrations tD and tD,tiss of metronidazole showed that for a given T, tD,tiss may be greater than or less than tD, depending on the dose, and that it is possible to obtain effective concentrations in the tissue compartment even though the infusion duration is too long to achieve effective concentrations in plasma. It was found that, depending on the dose, it was possible to cause an increase in tD,tiss compared with bolus administration by increasing the infusion duration of the dose. It was also found that increasing T could cause opposite changes in tD and tD,tiss (compared with bolus administration, respectively), e.g., an increase in tD and a decrease in tD,tiss or vice versa, depending on the dose. It should thus be possible to make precise predictions of the influence of T on drug concentration at the effector site for individual drugs by incorporating effect compartment modeling into the analysis.

Relationships among duration of infusion, dose, dosing interval, and steady-state plasma concentrations during intermittent intravenous infusions: studies with metronidazole

Relationships among duration of infusion (T), dose, dosing interval (tau), maximum and minimum plasma drug concentrations at steady state (Cmax,ss and Cmin,ss, respectively), and the duration of effective plasma concentrations (tD) during multidose intermittent infusion regimens were studied by computer simulation using metronidazole as a model drug. Pharmacokinetic parameter values for metronidazole were obtained from the literature and the minimum effective plasma concentration (MEC) was taken as 6.0 micrograms/ml. Increasing the infusion period of the dose reduces Cmax,ss, but increases Cmin,ss. If intermittent bolus injection of a given dose of drug results in effective plasma concentrations for the entire dosage interval (i.e., Cmin,ss,bolus greater than MEC), then infusion of that dose over any period (T less than or equal to tau) will also result in effective concentrations for the entire dosage interval. However, if the dosage is such that Cmin,ss,bolus less than MEC, the relationships among duration of infusion, dose, dosage interval, and duration of effective plasma concentrations are complex. Therefore a nomogram was developed to allow selection of dose, dosing interval, and infusion period such that Cmax,ss and Cmin,ss could be maintained within a desired range.