Community nephrology: audit of screening for renal insufficiency in a high risk population

BACKGROUND

The rate of acceptance onto dialysis programmes has doubled in the past 10 years and is steadily increasing. Early detection and treatment of renal failure slows the rate of progression. Is it feasible to screen for patients who are at increased risk of developing renal failure? We have audited primary care records of patients aged 50-75 years who have either hypertension or diabetes, and are therefore considered to be at high risk of developing renal insufficiency. Our aim was to see whether patients had had their blood pressure measured and urine tested for protein within 12 months, and plasma creatinine measured within 24 months.

METHODS

This was a retrospective study of case notes and computer records in 12 general practices from inner and greater London. A total of 16,855 patients were aged 50-75 years. From this age group, 2693 (15.5%) patients were identified as being either hypertensive or diabetic, or both.

RESULTS

Of the 2561 records audited, 1359 (53.1%) contained a plasma creatinine measured within 24 months, and 11% of these (150) had a value > 125 micromol/l. This equates to a prevalence of renal insufficiency of > 110,000 patients per million in this group. Forty two patients (28%) had been referred to a nephrologist. Of records audited, 73% contained a blood pressure measurement and 29% contained a test for proteinuria within 12 months.

CONCLUSIONS

There is a high prevalence of chronic renal insufficiency in hypertensive and diabetic patients. It is feasible to detect renal insufficiency at a primary care level, but an effective system will require computerized databases that code for age, ethnicity, measurement of blood pressure and renal function, as well as diagnoses.

Mechanisms of induction of renal allograft tolerance in CD45RB-treated mice

BACKGROUND

Rejection is the most significant problem in the field of transplantation. The current goal of transplant immunology is to develop better immunotherapeutic protocols that are aimed at specifically suppressing alloreactivity and preserving an otherwise intact immune system. We have previously shown that mice will accept renal allografts indefinitely with normal renal function after two injections of a monoclonal antibody to the CD45RB protein. Furthermore, this antibody will reverse acute rejection when therapy is delayed until day 4 and will still induce tolerance. The mechanisms of this therapeutic benefit are not known.

METHODS

BALB/C mice were used as recipients of major multiple histocompatibility complex-mismatched kidneys using C57BL/6 as donors. Immunoperoxidase microscopy and Northern blots for cytokine gene expression were used to study the renal allografts. Fluorescence-activated cell sorter (FACS) analyses of peripheral blood lymphocytes were performed. Phosphotyrosine peptide phosphatase assays were performed on splenic lymphocyte membranes.

RESULTS

A CD45RB monoclonal antibody (MB23G2) induced tolerance and partially depletes peripheral blood lymphocytes. A therapeutically ineffective CD45RB monoclonal antibody (MB4B4) merely coated the circulating lymphocytes. Furthermore, MB23G2 stimulated more tyrosine phosphatase activity than MB4B4 in mouse T-cell membranes.

CONCLUSIONS

The clearance of peripheral blood lymphocyte populations and stimulation of protein tyrosine phosphatase activity may be important in the mechanism of tolerance induction by CD45RB therapy, which may be clinically relevant in the therapy of organ rejection in humans.

Bacterial superantigens induce down-modulation of CC chemokine responsiveness in human monocytes via an alternative chemokine ligand-independent mechanism

Staphylococcal superantigens (SAgs) are very potent T cell mitogens, but they can also activate monocytes by binding directly to MHC class II molecules in a manner independent of TCR coengagement. Induction of proinflammatory cytokines and chemokine expression in monocytes by superantigens has recently been reported. Here we report that superantigen stimulation of human peripheral blood monocytes results in a rapid, dose-dependent, and specific down-regulation of chemokine (macrophage inflammatory protein-1alpha (MIP-1alpha), monocyte chemotactic protein-1 and MIP-1beta) binding sites (e.g., CCR1, CCR2, and CCR5), which correlates with a concomitant hyporesponsiveness of human monocytes to these CC chemokine ligands. This down-regulation occurs 15-30 min following superantigen stimulation and is specific to chemokine receptors, in that binding and responsiveness of monocytes to the chemoattractant formyl-tripeptide FMLP are not affected. We further demonstrate that SAg-induced down-modulation of chemokine binding and monocyte hyporesponsiveness to the chemokines MIP-1alpha, monocyte chemotactic protein-1, and MIP-1beta is mediated through cellular protein tyrosine kinases, and the down-modulation can be mimicked by an MHC class II-specific mAb. Additionally, our observations indicate that SAg-induced loss of chemokine binding and monocyte responsiveness is probably mediated by secreted serine proteinases. Bacterial SAg-induced down-modulation of chemokine responsiveness represents a previously unrecognized strategy by some bacteria to subvert immune responses by affecting the intricate balance between chemokine and chemokine receptor expression and function.

Bacterial Superantigens Induce Down-Modulation of CC Chemokine Responsiveness in Human Monocytes Via an Alternative Chemokine Ligand-Independent Mechanism

Staphylococcal superantigens (SAgs) are very potent T cell mitogens, but they can also activate monocytes by binding directly to MHC class II molecules in a manner independent of TCR coengagement. Induction of proinflammatory cytokines and chemokine expression in monocytes by superantigens has recently been reported. Here we report that superantigen stimulation of human peripheral blood monocytes results in a rapid, dose-dependent, and specific down-regulation of chemokine (macrophage inflammatory protein-1α (MIP-1α), monocyte chemotactic protein-1 and MIP-1β) binding sites (e.g., CCR1, CCR2, and CCR5), which correlates with a concomitant hyporesponsiveness of human monocytes to these CC chemokine ligands. This down-regulation occurs 15–30 min following superantigen stimulation and is specific to chemokine receptors, in that binding and responsiveness of monocytes to the chemoattractant formyl-tripeptide FMLP are not affected. We further demonstrate that SAg-induced down-modulation of chemokine binding and monocyte hyporesponsiveness to the chemokines MIP-1α, monocyte chemotactic protein-1, and MIP-1β is mediated through cellular protein tyrosine kinases, and the down-modulation can be mimicked by an MHC class II-specific mAb. Additionally, our observations indicate that SAg-induced loss of chemokine binding and monocyte responsiveness is probably mediated by secreted serine proteinases. Bacterial SAg-induced down-modulation of chemokine responsiveness represents a previously unrecognized strategy by some bacteria to subvert immune responses by affecting the intricate balance between chemokine and chemokine receptor expression and function.

[Recurrent urothelial cancer after resection of ureteral carcinoma]

OBJECTIVE

To prevent and treat recurrent urothelial cancer after resection of ureteral carcinoma, recurrence-associated factors and their features were analyzed.

METHODS

Thirty five cases of ureteral cancer were studied retrospectively.

RESULTS

There were 16 cases of recurrent bladder cancer among 32 cases after kidney-ureter and partial bladder removal. Bladder cancer recurred in 10 of 14 cases (71.4%) with multiorgan urothelial cancers. Six out of 18 cases with single ureteral cancer had recurrent cancer in the bladder. In 5 of the 6 cases, the primary tumor was located at the lower ureter. None of the 4 cases in grade I had tumor recurrence while there were 16 cases of recurrent bladder cancer in 28 cases in grade II-III. There was one recurrent bladder cancer in 6 cases in stage T1 within 2 years after operation. Among 26 cases in stage T2-T3, 10 cases of recurrent bladder cancer occurred in 2 years. After 2 years, 5 recurrent cases were in stage T1-T2. There were 2 recurrent urothelial carcinomas in 3 cases whose tumors were removed by local resection. The time of recurrence was 3 months to 6.5 years (average 1.86 years). Of 16 cases with recurrent urothelial cancer, 3 were alive for more than 3 years after operation. Of 8 cases without recurrence 6 survived for more than 3 years.

CONCLUSION

Recurrent urothelial cancer after resection of ureteral cancer occurs more frequently when the neoplasm is located in the lower ureter, involving more than one organ, with high-grade cell differentiation and high invasiveness. Prognosis of recurrent urothelial cancer is poor. Regular cystoscopic check-up is helpful to find the recurrence.

Secretoneurin and chemoattractant receptor interactions

Secretoneurin (SN) is a 33-amino acid peptide derived from secretogranin II (chromogranin C) which induces chemotaxis of monocytes but not neutrophils. In this study, we found that SN interacted with specific cell surface binding sites on human monocytes. The chemoattractants MCP-1, MCP-2 or fMLP could not compete for SN binding sites suggesting SN may bind to a novel chemotactic receptor. Additional studies showed that neither SN nor MCP-2 induced a rise in cytosolic Ca2+, and chemotaxis to SN was inhibited by cholera toxin (CT) and pertussis toxin (PT). Chemotactic desensitization studies demonstrated that fMLP, MCP-1, SN, and MCP-2 could all desensitize monocytes to subsequent SN stimulation. Our results indicate that SN binds to a cell surface receptor expressed on monocytes and activates signaling pathways which are sensitive to CT and PT.

Regulation of CCR2 chemokine receptor mRNA stability

During inflammatory and immunological responses, leukocytes respond to external stimuli by altering the stability of cytokine and cytokine receptor messages. Change in message stability is an effective mechanism for rapidly regulating steady state levels of mRNA. Cytokine messages containing A-U-rich elements located in the 3' untranslated region (ARE) are the best studied examples of this process. AREs have been shown to act as targeting motifs for degradation of cytokine and transcription factor messages. We have recently observed that the interleukin-8 (IL-8) receptor messages, IL-8RA and B (CXCR1 and CXCR2), also undergo changes in stability in response to the inflammatory stimulator lipopolysaccharide (LPS). To determine whether regulation of message stability is a common mechanism for modulation of chemokine receptor mRNA we explored whether the stability of the CC chemokine receptor message for CCR2 (monocyte chemotactic protein-1 receptor) is also regulated by LPS. We found that LPS induces a rapid loss of steady state levels of CCR2 message through message degradation. Furthermore, LPS stimulated the decay of Poly(A) CCR2 mRNA faster than total CCR2 RNA, indicating that deadenylation is the first step in LPS-induced CCR2 RNA degradation. We conclude from these experiments that LPS stimulates the rapid degradation of CCR2 messages through a two-step process, deadenylation followed by degradation of the message body. In contrast to the results obtained for CCR2 mRNA, macrophage inflammatory protein-1alpha messages, which contain an ARE motif, were stabilized by LPS stimulation, indicating that chemokine and chemokine receptor mRNA stability are regulated by different and opposing mechanisms.

The 3' untranslated region of the human poly(ADP-ribose) polymerase gene is a nuclear matrix anchoring site

The nuclear matrix displays the most dramatic changes among all cellular structures during carcinogenesis. Matrix attachment regions (MARs) organize chromatin into domains, harbor origins of replication and display a notable transcriptional enhancer activity. To understand the nature of MARs and their involvement in gene expression, replication, and carcinogenesis, we have cloned the MAR DNA fragments, of a size of 0.1-5.0 kb, isolated from human cells in culture. Over 150 clones have been sequenced. One MAR clone was identified as a stretch of 393 bp from the 3' untranslated region (3' UTR) of the human poly(ADP-ribose) polymerase (PARR) gene (100% homology). The 393 bp MAR fragment contains several repeats of TTGTTTTGT and related sequences (the TG boxes) and motifs with similarity to the binding site of the general yeast transcription factor GFI and to the ARS origins of replication in yeast. In addition, the 3' UTR of the PARP gene harbors MAR-type sequences found in other genes, kinked and curved DNA, two imperfect inverted repeats, and short alternating GA- and CT-rich motifs. The presence of TG-, GA-, and CT-rich motifs and of potential cruciforms is proposed to identify a novel type of MAR sequence. This report suggests that MAR sequences may reside in the 3' untranslated region of other genes and has important implications for a potential role of the nuclear matrix in transcription termination.

[Clinical importance of p53 gene mutation and PCNA expression in ureteral and renal pelvic cancers]

In order to know the clinical importance of p53 gene mutation and PCNA expression in ureteral and renal pelvic cancers, research was carried out with immunohistochemistry S-P method in 45 cases. Mutant p53 nuclear staining was positive in 24 cases (53.3%) and correlated with PCNA expression, being higher in clinical stages T3 and T4 than in T1 + T2. They also correlated with the grade of cell differentiation, being higher in G3 than in G1 + G2.

Ambulatory blood pressure profiles and plasminogen activator inhibitor (PAI-1) activity in lean women with and without the polycystic ovary syndrome

OBJECTIVE

Hyperinsulinaemic women with the polycystic ovary syndrome (PCOS) may be at increased risk of vascular disease later in life, mediated by blood pressure or lipid abnormalities or by elevated plasma levels of plasminogen activator inhibitor-1 (PAI-1) activity. PAI-1 may also be involved in ovarian follicle development and ovarian connective tissue remodelling. We measured plasma PAI-1 activity and 24-hour ambulatory blood pressure records in women with and without PCOS.

DESIGN

Cross-sectional study of three groups.

PATIENTS

Twenty-four non-obese women with a classic ovarian ultrasound appearance of PCO and extreme menstrual disturbance (Group 1), 26 matched controls with a normal menstrual cycle and an ultrasound appearance of PCO (Group 2) and 10 matched controls with a normal menstrual cycle and normal ovarian ultrasound (Group 3).

MEASUREMENTS

Twenty-four hour ambulatory blood pressure recordings (Spacelabs 90207), ovarian ultrasonography, fasting plasma insulin and glucose, plasma PAI-1 activity, HDL and total cholesterol, triglycerides, gonadotrophins and testosterone. Family history of premature vascular disease.

RESULTS

Median fasting plasma insulin was significantly higher in Group 1 (45.8 pmol/l, range 12.9-161.9) than in Group 2 (28.1 pmol/l; range 13.6-91; P < 0.05) or Group 3 (26.0 pmol/l; range 13.5-63.3; P < 0.05). There were no differences between groups in 24-hour, daytime or night-time ambulatory blood pressure measurements, and no relation between plasma insulin and any blood pressure variable. Mean plasma PAI-1 activity was higher in Group 1 (10.0 +/- 7.1 AU/l) than in Group 2 (6.0 +/- 4.6 AU/l; P < 0.05) or Group 3 (5.1 +/- 3.5 AU/l; P = 0.06). There was a significant independent direct relation between fasting plasma insulin and PAI-activity (r = 0.41, R2 = 0.154; F1,59 = 11.38; P = 0.001). Groups did not differ in parental history of premature vascular disease, or in mean HDL or fasting triglyceride levels.

CONCLUSIONS

The only measurable vascular risk factor associated with hyperinsulinaemia and menstrual disturbance in non-obese women with PCOS is an elevated plasma PAI-1 activity. These women did not differ from controls in ambulatory blood pressure profiles, lipid measurements or in a parental history of premature vascular disease. PAI-1 and plasminogen are involved in ovarian follicle maturation and the present finding suggests a biologically plausible link between hyperinsulinaemia, anovulation and vascular risk in PCOS.

[Expression and clinical significance of PCNA in renal pelvic and ureteral cancer]

To determine the relationship between PCNA expression and pathological stage, cellular grade, recurrence and prognosis of renal pelvic and ureteral cancer, research on PCNA proliferating index in 47 cases of renal pelvic and ureteral cancer we studied by immunohistochemistry S-P method. PCNA proliferating index of renal pelvic and ureteral cancer increased with pathologic stage and cellular grade. PCNA proliferating index of T3 + T4 was significantly higher than that of T1 + T2 (P < 0.01). PCNA proliferating index of G3 was significantly higher than that of G1 + G2 (P < 0.001). Those with higher PCNA proliferating index (III + IV) had higher bladder cancer recurrent rate after operation (60%, 12/20), those with lower PCNA proliferating index (I + II) had lower bladder cancer recurrent rate (22.2%, 6/27). P < 0.01. 35% (7/20) of those with III + IV PCNA proliferating index had simultaneous polyorganic urothalial cancer, 7.4% (2/27) of those with I + II PCNA proliferating index had simultaneous polyorganic urothelial cancer, P < 0.05. 7.4% (2/27) of those with I + II PCNA proliferating index had local recurrence and metastasis after operation, 40% (8/20) of those with III + IV had local recurrence and metastasis, P < 0.05. The 5-year survival rate of I + II was 86.7%, the 5-year survival rated of III + IV was 35.7% (5/14), P < 0.05. The findings suggest that PCNA proliferating index connects with pathological stage and cellular grade of renal pelvic and ureteral cancer. It is an important characteristic of low differentiation, invasiveness and simultaneous or sequentially polyorganic urothelial cancer. It may be an important prognostic indicator of renal pelvic and ureteral cancer.

Benign mixed tumor (pleomorphic adenoma) of the lacrimal gland in a 6-year-old boy

PURPOSE

To report a 6-year-old boy who had benign mixed tumor (pleomorphic adenoma) of the lacrimal gland.

METHODS

A 6-year-old boy was referred for evaluation of a lacrimal fossa mass. We performed a lateral orbitotomy and excised the mass.

RESULTS

Histopathologic evaluation of the excised orbital mass disclosed a benign mixed tumor (pleomorphic adenoma) of the lacrimal gland.

CONCLUSION

Benign mixed tumors (pleomorphic adenomas) of the lacrimal gland are rare in children. However, they must be considered in the differential diagnosis of pediatric orbital masses because of the prognostic importance of removing a pleomorphic adenoma with the capsule intact.

[Non-functioning adrenal tumor: clinical analysis of 29 cases]

29 patients with adrenal tumors were admitted to our hospital from June 1985 to July 1994. The diagnosis was made preoperatively in 7 patients (5 adrenal cyst, 2 adrenal myelolipoma) by B-US, CT or MRI. Of the 22 patients whose diagnosis was not made before operation, 8 (tumor diameter: < 3cm) had adrenal cortical adenomas, 6 (tumor diameter: 3-6cm) adrenal medullary tumor, 8 (tumor diameter: > 6cm) adrenocortical cancer (2), adrenal neuroblastoma (1), metastatic cancer (2), adrenal pheochromocytoma (1) and adrenal lymphatic hyperplasia (1) respectively. All non-functioning adrenal tumors should be treated operatively except for adrenal cyst smaller than 3 cm or adrenal myelolipoma.

Byssinosis in Guangzhou, China

OBJECTIVES

To study the prevalence of byssinosis and other respiratory abnormalities in workers exposed to cotton dust in Guangzhou in two factories that processed purely cotton.

METHODS

All the 1320 workers exposed were included. The controls were 1306 workers with no history of occupational dust exposure. Total dust and inhalable dust were measured by Chinese total dust sampler and American vertical elutriator respectively. A World Health Organisation questionnaire was used. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by a Vitalograph spirometer.

RESULTS

The median inhalable dust concentrations ranged from 0.41 to 1.51 mg/m3 and median total dust concentrations from 3.04 to 12.32 mg/m3. The prevalence of respiratory abnormalities in the cotton workers were (a) typical Monday symptoms 9.0%; (b) FEV1 fall by > or = 5% after a shift 16.8%; (c) FEV1 fall by > or = 10% after a shift 4.2%; (d) FEV1 < 80% predicted 6.1%; (e) FEV1/FVC < 75% 4.0%; (f) cough or phlegm 18.2%; (g) chronic bronchitis 10.9%; and (h) byssinosis, defined by (a) plus (b) 1.7%. With the exception of (d), most of the prevalences increased with increasing age, duration of exposure, and cumulative inhalable dust exposure. No increasing trends of respiratory abnormalities were found for current total dust, inhalable dust, and cumulative total dust concentrations. Compared with controls, after adjustment for sex and smoking, with the exception of (d), all the pooled relative risks of respiratory abnormalities were raised for cotton exposure.

CONCLUSION

It is concluded that cumulative inhalable cotton is likely to be the cause of byssinotic symptoms, acute lung function decrements, cough, or phlegm, and chronic bronchitis.

A novel class of matrix attached regions (Mars) identified by random cloning and their implications in differentiation and carcinogenesis

MARs, i.e., the attachment points of chromatin loops to the insoluble nuclear suprastructure called nuclear matrix, define the borders between domains, are the sites of initiation of DNA replication, and display transcriptional enhancer activity. MARs play an important role in differentiation and in carcinogenesis. MAR-protein complexes were proposed to interact with proteins bound to the immediate upstream regulatory region of active genes and bring the 5' end of active genes onto the nuclear matrix where transcription factors and RNA polymerases are located. We have isolated the nuclear matrix from human K562 cells, comprising 1-2% of nuclear DNA, after removal of the bulk of nuclear polynucleosomes with micrococcal nuclease. The MAR DNA was cloned in E. coli. We report here the sequence of a MAR fragment of 480 bp (clone Hum. MAR 19.2a). This sequence contains homopurine stretches of 5-10 nt alternating with homopyrimidine stretches of 4-17 nt, favoring formation of cruciform structures on the DNA. We have identified seven potential cruciform structures, characteristic elements of origins of replication, on the 480 bp 19.2a fragment. In addition this MAR clone contains three ATTA-type motifs representing homeodomain protein binding sites and five TG-rich (or its complementary CA-rich) stretches that we call TG boxes. TG boxes are found at recombination sites. in chromosome telomeres, and in the binding sites of a class of protein factors that regulate transcription and replication. The present study showing a multitude of potential cruciform structures characteristic of origins of replication in the Hum. MAR 19.2a clone gives further support to the idea that a subset of human MARs may function as origins of DNA replication. The relevance of these studies to carcinogenesis and differentiation are discussed.

Altered gentamicin pharmacokinetics during the perioperative period

The effect of surgery on the pharmacokinetics of gentamicin sulfate in hospitalized patients was studied. Patients with cancer undergoing surgery of the head and neck were given gentamicin sulfate in doses calculated to achieve peak serum concentrations of 6-8 micrograms/mL and trough concentrations of 1-2 micrograms/mL. Each patient received a loading dose at the time of surgical incision, followed by five maintenance doses at eight-hour intervals. Steady-state peak and trough serum gentamicin concentrations were predicted using a one-compartment open pharmacokinetic model and literature values for volume of distribution (V) and first-order elimination rate constant (k). Serum gentamicin concentrations were measured 0.25 hours before and at 0.5, 3.5, and 6.5 hours after completion of infusion of the second maintenance dose. Peak and trough serum concentrations were obtained by extrapolation from these measured concentrations using weighted, nonlinear least squares regression. Predicted versus measured serum gentamicin concentrations and estimated versus observed values for V and k were compared. Eight men and seven women had evaluable serum gentamicin concentrations. Patients received a mean calculated maintenance dose of 4.4 +/- 0.7 mg/kg/day. Mean extrapolated peak and trough serum gentamicin concentrations were significantly lower than predicted, and observed values of V and k were significantly greater than estimated values. Gentamicin dosages calculated using standard pharmacokinetic variable values may not produce therapeutic concentrations in patients undergoing surgery. Monitoring of serum concentrations with dosage adjustment when indicated is necessary for optimal therapy in these patients.

Undetected episodes of prolonged apnea and severe bradycardia in preterm infants

Twenty-four-hour tape recordings of ECG and breathing movement were made on 14 preterm infants with prolonged apneic episodes. Despite apnea monitoring systems, 136/203 (67%) apneic episodes greater than or equal to 20 seconds in duration, including 19 episodes greater than or equal to 50 seconds in duration, were not recorded by nursing staff. Of 120 apneic episodes greater than or equal to 30 seconds, 100 (89%) were accompanied by bradycardia less than or equal to 100 beats per minute. Episodes of more marked bradycardia (less than or equal to 80 beats per minute and up to seven minutes in duration) occurred without cessation of breathing movement in 10/14 infants studied. Treatment with theophylline or aminophylline was associated with a reduction in the number of episodes of apnea greater than or equal to 20 seconds accompanied by bradycardia less than or equal to 80 beats per minute (P less than .001). Many prolonged episodes of apnea and bradycardia are going unnoticed in neonatal intensive care units. Further studies are required to investigate and overcome the causes of these failures.

Disposition and removal of metronidazole in patients undergoing haemodialysis

The pharmacokinetics and haemodialysis clearance of metronidazole were investigated in four renal failure patients after a single 500 mg intravenous dose and in two renal failure patients on continuous treatment with metronidazole. During dialysis, the volume of distribution of metronidazole was 0.60 +/- 0.04 l/kg, total clearance was 196.0 +/- 60.6 ml/min and the elimination half-life had an harmonic mean of 2.14 h. Extraction across the dialyser was 51.5 +/- 7.8% and was limited to the distribution of drug in plasma water. Dialysis clearance was 125.0 +/- 32.7 ml/min, which represented 62 +/- 6% of total clearance and was 1.75 times the sum of the other clearance mechanisms. The hydroxy metabolite was extracted and cleared by the dialyser to the same degree as metronidazole itself. During the 4 h-dialysis 44.9 +/- 2.6% of the dose was removed by the dialyser in the four patients administered a single dose. Metronidazole is efficiently cleared and extensively removed by dialysis, and therefore dosage adjustments and alterations in the timing of dosage administration are essential in patients undergoing haemodialysis.