[Idiopathic hypercalciuria and bone density]

A decrease in bone density of the spine has been reported in individuals with hypercalciuria and the finding of the latter in osteoporosis patients is not uncommon. We studied 21 men and 8 women (mean age 47 +/- 13) with idiopathic hypercalciuria (IHCU) defined by an urinary calcium of more than 7.5 mmol/24 h in men and 6.25 mmol/24 h in women. The duration of IHCU was 10 (+/-) 8 years. Among the 29 patients, 24 had one or more renal calculi. Twenty one had been treated, by low calcium diet only (and diuresis), combined with a thiazide diuretic, or sodium phytate, or phosphorus. Bone mineral content (BMC) was measured in the lumbar spine and the upper end of the femur using an ORIS ODC 200 densitometer and compared with 29 control subjects paired for age and sex. No difference was found between the two groups concerning BMC values in either the spine or the 3 femoral sites (neck, Ward, trochanter). BMC was not correlated with urinary calcium. Thus individuals with IHCU showed no decrease in their bone mass, among this group seen in a department of nephrology. The influence of the treatment of IHCU remains to be defined.

Relationship between renal function and disposition of oral cefixime

The pharmacokinetics of cefixime following a single oral dose of 200 mg have been investigated in 6 normal subjects and in 22 patients with various degrees of renal insufficiency. Serum and urine samples were collected between 0 and 72 h and were subjected to two methods of analysis: bioassay and HPLC. There was a linear relationship between the two sets of results from 228 samples. This result suggests that none of the metabolites, which may accumulate in uraemic patients, has antibacterial activity. In normal subjects, the peak serum level (Cmax) was 2.50 micrograms.ml-1 at 2.83 h (tmax); the apparent elimination half-life (t1/2) was 3.73 h; the apparent total body clearance (CL.f-1) was 154 ml.min-1, the mean renal clearance (CLR) was 39.1 ml.min-1 and the apparent fraction of the dose recovered in 24 h urine was 0.22. In uraemic patients, Cmax and tmax were slightly increased and t1/2 was increased to 12-14 h in patients with an endogenous creatinine clearance below 20 ml.min-1. The apparent volume of distribution was decreased. Apparent total and renal clearances were lower in proportion to the degree of renal insufficiency. Linear relationships were found between CL/f, CLR and creatinine clearance (CLCR). The findings suggest that the dose of cefixime needs to be reduced only in patients with severe renal failure.

[Value of renal biopsy in the elderly. 32 cases]

Between November 1985 and November 1989, percutaneous renal biopsy was performed in 32 patients aged 75 or more (mean age 78). The major clinical presentations were nephrotic syndrome in 22 patients, variable amounts of proteinuria in 6 patients and unexplained severe renal insufficiency in 4 patients. In 27 cases the histological study revealed a glomerular disease. Minimal change disease (7 cases), membranous nephropathy (6 cases), amyloidosis (5 cases) and crescentic glomerulonephritis were the most frequent types. The rate of complications after biopsy was low (3 percent) with only one retroperitoneal hematoma. Owing to the atypical renal presentation of some glomerulopathies in the elderly, renal biopsy was useful to differentiate between minimal change disease, membranous nephropathy and amyloidosis. In 4 patients with minimal change disease, remission of nephrotic syndrome was obtained with corticosteroids. Moreover renal biopsy allowed to detect underlying diseases and gave indications to initiate specific therapy particularly in crescentic glomerulonephritis the outcome of which remained unfavourable. It is concluded that, even in elderly, renal biopsy is a valuable and safe diagnostic tool to obtain a rapid diagnosis, particularly in glomerular diseases, leading to a biopsy-guided therapy. It must therefore have the same indications as in younger adults with glomerular syndrome or rapidly progressive renal insufficiency.

[Indications for angiographic study of renal arteries in elderly hypertensive subjects]

During a 30 months period, 70 patients (60-84 years old) underwent a renal artery angiographic investigation, either by combined intravenous angiography and pyelography, either by intravenous or intra-arterial digital angiography. Thirty-nine were males, 31 were females. All patients were hypertensive. Thirty-three had a normal renal function and 37 had a renal insufficiency arbitrarily definite as creatinine clearance lower than 60 ml/min (m = 33 +/- 15 ml/min). Eight aortic anevrysms were discovered. Thirteen patients (18.6%) had atherosclerotic renovascular disease. Criteria which led to undertake these investigations and results are listed in the following table. [table; see text] Transluminal percutaneous angioplasty and surgical treatment were performed 7 and 3 times respectively. In one case, nephrectomy was done. In all these patients but one, improvement of hypertension and/or renal function occurred. In patients with renal impairment, difference in size between the two kidneys detected by echography or plain abdominal X-rays were noted in 8 among the 9 patients with renovascular disease; six among them had proteinuria less than 0.5 g/day. In conclusion, in hypertensive patients older than 60, criteria for detection of renovascular disease are the same as in younger patients. When renal function is decreased, difference in size between the two kidneys requires an angiographic evaluation. Proteinuria does not exclude renovascular pathology.

Anti-myeloperoxidase antibodies: immunological characteristics and clinical associations

Antibodies directed against myeloperoxidase (anti-MPO) were detected, using a solid-phase ELISA and purified sputum myeloperoxidase as the substrate, in 54 sera from 22 patients. Anti-MPO were present in 17 patients with crescentic glomerulonephritis (CGN), Wegener's granulomatosis (WG) and microscopic polyarteritis (MPA), and thus are associated with different forms of vasculitis. Anti-MPO were also present in five out of 20 patients with systemic lupus erythematosus (SLE). Anti-MPO activity in SLE sera was low, in contrast to the high titers observed in patients with vasculitis. All positive sera had IgG anti-MPO (except two SLE sera) and most of them also contained low-titered IgM anti-MPO. Only three patients had high IgM anti-MPO activities, the significance of which remains to be determined. In patients with CGN, WG or MPA, the anti-MPO titer decreased following therapy and paralleled the disease activity. Thus, anti-MPO constitute a useful diagnostic tool and a sensitive marker of disease activity in this group of patients with vasculitis.

Total and ultrafiltrable plasma magnesium in hyper- and hypoparathyroidism, and in calcium-related metabolic disorders

Serum total, ultrafiltrable and protein-bound magnesium, and urinary fractional excretion of magnesium were studied in patients with primary hyperparathyroidism (before and after surgery) and in patients with hyperparathyroidism, malignant hypercalcemia and chronic renal failure with or without hemodialysis. Whereas serum total Mg was unchanged in patients with primary hyperparathyroidism, the ultrafiltrable magnesium concentration was higher than in the control group and higher before than after surgery. The total and the ultrafiltrable magnesium concentrations were highly correlated in the overall patients with Ca-related metabolic disorders, suggesting that renal function had no influence on the relation between these two parameters. Moreover, in malignant hypercalcemia, our results suggested that PTH-like peptides might be less effective than PTH in renal handling of Mg as previously described for Ca.

Acute renal thrombosis induced by angiotensin-converting enzyme inhibitors in patients with renovascular hypertension

Acute reversible renal failure is a widely recognized potential complication of angiotensin-converting enzyme inhibitor (ACEI) administration in renovascular hypertension, particularly in bilateral artery stenosis or stenosis involving a solitary kidney. We report herein 2 cases of a rare but severe complication, i.e., acute renal artery thrombosis. Whereas marked hypotension does not seem to be necessary to trigger acute renal failure following ACE inhibition, by contrast, the fall in blood pressure could play an important role in our patients. Since single-dose ACEI has been advocated in order to improve the predictive value of renal scintigraphy or plasma renin activity measurements in the diagnosis of renovascular hypertension, the potential risk of this approach should be stressed.

Chronic effects of tertatolol on renal function in hypertensive patients with mild chronic renal failure

To assess the potential benefit of drug-induced renal haemodynamic changes in patients with chronic renal failure, we have evaluated the effects of the beta-blocking agent tertatolol on blood pressure, glomerular filtration rate, and renal plasma flow. Inulin and PAH clearances were performed before and after 3 months treatment and oral tertatolol, 5 mg daily in eight hypertensive patients with moderate chronic renal failure. After 3 months of treatment, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) increased significantly by 10% and 13% respectively, whereas renal vascular resistance decreased by 16% and the filtration fraction was unchanged. These results indicate that tertatolol possesses novel renal haemodynamic properties in hypertensive patients with chronic renal failure. However, the long-term benefit of such a therapy is yet to be confirmed.

Disposition of fleroxacin, a new trifluoroquinolone, and its metabolites. Pharmacokinetics in renal failure and influence of haemodialysis

The pharmacokinetics of fleroxacin and its metabolites following a single oral dose of fleroxacin 400mg were examined in 6 healthy subjects and 24 patients with various degrees of renal insufficiency. Plasma and urine samples, collected at various times after administration, were assayed by high performance liquid chromatography (HPLC). In healthy subjects, Cmax was 6.8 +/- 0.7 mg/L; tmax = about 1h, t1/2 = 14 +/- 2h, total clearance = 4.86 +/- 0.72 L/h and the percentage of unchanged fleroxacin excreted in urine in 48 hours was 48 +/- 4% (HPLC). Plasma concentrations of metabolites were very low and accounted for no more than 5% of the levels of unchanged fleroxacin. In uraemic patients Cmax did not change, whatever the degree of renal failure; tmax was increased in patients with a glomerular filtration rate below 0.6 L/h, and Vd/f was independent of the severity of renal failure. These data suggest that bioavailability of the drug is unchanged. In uraemic patients t1/2 was prolonged and AUC multiplied by a factor of 2 to 3. A linear relationship was found between total and renal clearances of fleroxacin and creatinine clearance. Accumulation of N-demethyl-fleroxacin and N-oxide-fleroxacin was very high in uraemic patients, due to slow formation of these metabolites and decreased urinary elimination. Dialysance of fleroxacin and of its metabolites was approximately 3.6 to 4.8 L/h. These findings suggest that fleroxacin dosage may need to be reduced in patients with severe renal disease; in haemodialysed patients, treated every 2 days, a single dose of fleroxacin 400mg is recommended at the end of each dialysis session.

Renal granulomatous sarcoidosis: report of six cases

Six cases of chronic renal failure related to granulomatous renal sarcoidosis are reported and compared with data in the literature. The particular features of sarcoidosis granulomatous interstitial nephritis should be emphasised because presentation may be misleading. Renal failure usually presents with a rapidly progressive course, either isolated or associated with mild proteinuria and sterile leukocyturia, while extrarenal localisations may be absent. Diagnosis should be suspected on the basis of elevated or paradoxically normal serum calcium concentrations, due to increased plasma concentrations of calcitriol, while immunoreactive circulating parathormone concentrations are depressed. Calcitriol as well as angiotensin-converting enzyme could represent unregulated secretion products from granulomatous tissue and their plasma concentrations may roughly reflect activity of the disease. Early corticosteroid treatment dramatically improves renal function but long-term renal prognosis may be oblitered due to progressive chronic renal failure related to fibrosis scarring.

Pharmacokinetics of cilazapril in patients with renal failure

1. The pharmacokinetics of a single 1 mg dose of cilazapril were determined in six subjects with normal renal function and in 19 uraemic patients with various degrees of renal impairment. 2. Significant decreases in systolic and diastolic blood pressure were noted in all groups of subjects between 2 and 8 h after administration of 1 mg cilazapril. 3. There was a significant correlation between ACE inhibition at 24 h and creatinine clearance (CrCL). 4. For cilazapril, Cmax and tmax were independent of creatinine clearance. AUC(24) was inversely related to CrCL and apparent plasma clearance (CL/F) was directly related to CrCL. 5. For cilazaprilat, Cmax and tmax were related to creatinine clearance. AUC(24) was inversely related to CrCl and apparent plasma clearance (CL/F) was directly related to CrCL. 6. Dialysis clearance was approximately 2 l h-1 for cilazapril and for cilazaprilat. 7. The effects of renal impairment on cilazapril and cilazaprilat kinetics were similar to those observed for other inhibitors of angiotensin-converting enzyme such as captopril, enalapril and lisinopril. 8. It may be necessary to modify doses of cilazapril for the treatment of essential hypertension in uraemic patients. When creatinine clearance was below 15 ml min-1 cilazaprilat concentrations were increased, half-lives were prolonged and ACE inhibition remained above 90% for at least 24 h. A reduced dosage is indicated for these patients. 9. In patients requiring haemodialysis, maintenance doses of 0.5 mg given after each haemodialysis session are sufficient.

Comparative pharmacokinetics of tromethamine fosfomycin and calcium fosfomycin in young and elderly adults

The pharmacokinetics of two oral forms of fosfomycin, tromethamine (trometamol) salt and calcium salt, were studied in five young (age, 29 +/- 3 [standard deviation] years) and eight elderly (age, 72 +/- 6 years) adults. The subjects received a single 40-mg/kg (body weight) (approximately equal to 3-g) calcium fosfomycin dose and a 25-mg/kg (approximately equal to 2-g) tromethamine fosfomycin dose in fosfomycin acid form. Blood and urine samples were collected for 24 h. Antibiotic concentrations in serum and urine were measured by microbiological assay. In all subjects, the peak levels of the calcium salt in serum were two- to fourfold lower than those of the tromethamine salt (6 to 7 and 18 to 22 micrograms/ml, respectively), indicating poor intestinal absorption of the calcium form. The elimination half-life of the two oral forms was about 5 h in young adults, and the half-life was only moderately longer in elderly subjects, with large individual variations: 8.28 +/- 5.51 h for tromethamine fosfomycin and 11.80 +/- 6.86 h for calcium fosfomycin. In elderly subjects, absorption of the tromethamine salt form was not modified, but the time to peak level was delayed for the calcium salt (2.58 +/- 0.54 h versus 1.41 +/- 0.67 h in young adults). Pharmacokinetic elimination of the two forms of fosfomycin was only moderately affected in elderly subjects; we observed lower urinary elimination, about 58 versus 28% of the dose in 24-h urines for the tromethamine salt and decreased renal clearance of both forms. However, the dosages of tromethamine and calcium fosfomycin need not be adjusted for elderly subjects who have endogenous creatinine clearances above 50 ml/min per 1.73 m2.

Is apalcillin nephrotoxic?

Apalcillin is a new semisynthetic penicillin used as a sodium salt. More than 4,000 patients have been treated with this antibiotic, but increased serum creatinine levels were noted in 18 cases. In 5 of these cases, apalcillin was possibly responsible, and in 13 it was doubtful. We decided to study renal function of normal volunteers treated with 4 g of apalcillin. Three periods were studied: a pretreatment control period of 80 min followed by a treatment period of 60 min and a posttreatment period of 40 min. Inulin and p-aminohippurate (PAH) infusion were continued during all three periods. At the beginning of the treatment period, 2 g of apalcillin was injected as a bolus, followed by infusion of 2 g of apalcillin over 1 h. Urinary volume was measured every 20 min. Creatinine, insulin, and PAH clearances and urinary excretion of sodium, potassium, calcium, and magnesium were calculated for each period. Urinary beta-2-microglobulin excretion was also assessed. Analysis of variance was done. We observed no variation in clearances of creatinine or inulin or in urinary electrolyte output. PAH clearance was significantly decreased during apalcillin infusion. Apalcillin appeared to compete with PAH for proximal tubular secretion but induced no further renal dysfunction.

[Renal complications of anti-cancer chemotherapy]

This review is not intended as a complete study of the nephrotoxicity of chemotherapy agents used in the treatment of cancer. The number of these drugs that are cytotoxic has considerably increased in the last few years and our information is incomplete for many of them. We therefore reviewed the observations reported in the literature. Cis-platinum, streptozotocin, methotrexate at high doses, mithramycin and mitomycin are highly nephrotoxic. Other drugs, such as nitrosoureas, celiptium are less nephrotoxic while some appear to rarely induce nephrotoxicity. Anticancer drug nephrotoxicity is characterized by its particular insidiousness, its time of occurrence and its evolution. Since no clinical manifestations accompany the lesions, nephrotoxicity must be sought routinely. It can occur early or late, may be constant as of the first course or appear only after a certain cumulative dose and even occasionally after such a long interval that its cause may appear to be in doubt. The severity of this nephrotoxicity ranges from the usual first minor urinary anomalies to terminal renal failure. The pathophysiogenic mechanisms of the nephrotoxicity remain in most cases obscure. The mode of penetration into the cells is not known. There are fewer data on the interaction between the toxic agent and the cellular metabolism. In most cases, the drug itself in unchanged form does not seem to be the causative agent, which appears rather to be its metabolite. These metabolites are not always identified. Thus nephrotoxicity of antitumoral agents has not been given sufficient attention. Only better knowledge of their action within the kidney will eventually lead to progress in preventing their harmful side effects.

[Acute systemic lupus erythematosus after thymectomy for myasthenia. Sequential study of lymphocyte subpopulations]

A 35 year-old woman developed severe systemic lupus erythematosus 9 years after thymectomy for myasthenia gravis. "Seric Thymic Factor" (STF) was low; T helpers subset, T helpers/T suppressors ratio and to a lesser extent T suppressors subset were decreased. Suppressor cell function investigated by Concanavaline A lymphocyte reactivity was low. Under cyclophosphamide, plasmapheresis and steroids all clinical and biological symptoms improved but STF remained low; T helpers, T suppressors subsets and T helpers/T suppressors ratio increased but did not reach the normal range. Statistical and immunological arguments suggest that the association between systemic lupus erythematosus and myasthenia gravis did not occur only by chance. Moreover, thymectomy might have played a role by decreasing the number and function of some subpopulations of lymphocytes.

Pharmacokinetics of aztreonam in patients with chronic renal failure

The elimination kinetics of aztreonam (SQ 26,776), a new, completely synthetic, monocyclic beta-lactam antibiotic, were studied after the administration of a single 1g intravenous dose. Five healthy volunteers and 20 patients with various degrees of renal insufficiency were enrolled in this study. Concentrations of aztreonam in serum and urine were determined by both microbiological and high pressure liquid chromatography (HPLC) assays. The pharmacokinetic parameters for aztreonam were calculated on the basis of a 2-compartment open model. Serum concentrations of aztreonam at 10 minutes after administration were approximately 100 micrograms/ml in all subjects, regardless of renal function (HPLC assay). The mean serum half-life during the alpha-phase showed no important variation with renal function. The mean serum half-life during the beta-phase was 1.8 hours in normal subjects and 8.4 hours in haemodialysis patients (HPLC assay). There was a linear correlation between the serum clearance of aztreonam and creatinine clearance. The mean cumulative urinary recovery of aztreonam in 48 hours was 60 to 70% of the administered dose in normal subjects but this was reduced in the presence of renal insufficiency. SQ 26,992, the microbiologically inactive metabolite of aztreonam resulting from hydrolytic opening of the beta-lactam ring, was undetectable in the serum of normal subjects but was found in low levels in uraemic patients. Half of a 1g intravenous dose of aztreonam was eliminated during 4 hours of haemodialysis. Guidelines for administration of aztreonam in the presence of renal failure are given.

Vegetating iodides after an intravenous pyelogram

A 68-year-old woman treated by hemodialysis for chronic renal failure received 30.4 g iodine for an intravenous pyelogram. Three days later, she was covered by aseptic pustules which quickly evolved into vegetating masses on the face. Skin pathology showed dermo-epidermal necrosis with dermal polymorphonuclear infiltrates, sometimes pycnotic, and necrotizing vasculitis. Serum iodine was far above normal values. Hemodialysis and local care resulted in good healing within 1.5 month. Four similar cases occurring in patients with renal failure are mentioned in literature.

[Pharmacokinetics of azlocillin in chronic renal failure and hemodialysis patients]

The pharmacokinetics of azlocillin were studied in 16 patients with varying degrees of renal impairment (creatinine clearance Ccr ranging from 0 to 52 ml/min/1.73 m2) and on and off sessions in 4 of these patients on periodical haemodialysis. A single dose of azlocillin 80 mg/kg was given by intravenous infusion over 30 min. Maximum concentrations in the sera of patients with renal impairment were the same as in normal subjects, ranging from 300 to 400 micrograms/ml. The elimination half-life (t 1/2) increased as renal function deteriorated, with values of 1.11 h in subjects with healthy kidneys to 5.66 h in patients with Ccr less than 15 ml/min (maximum 8.38 h). The apparent volume of distribution (Vd) was unchanged in patients with renal impairment but was significantly increased in patients on haemodialysis. The mean percentage of the dose administered excreted in the urines decreased from 60-70% in normal subjects to about 11% in patients with severe renal failure, but urinary concentrations remained above therapeutic levels. The extra-renal elimination of azlocillin was unmodified by renal impairment. Azlocillin is easily removed by dialysis: t 1/2 values between and during 6 h sessions of haemodialysis were 6.55 h and 2.81 h respectively, corresponding to a 45.8% extraction on the dialyser. These results are comparable to those found in the literature and can be used as a basis for adjusting azlocillin dosage to the degree of renal function.

Partial deficiency of the fourth component of human complement (C4) and autoantibody directed against C4 in a patient with SLE

The finding of dramatically depressed levels of C4 in a 17-year old patient with severe systemic lupus erythematosus (SLE) prompted a genetic study of her family. This study revealed the existence of a partial C4 deficiency; we found the presence of a C4A3,C4BQo haplotype which was transmitted by the mother to each of her children. This patient possessed, in her serum, an autoantibody with anti-C4 specificity. The immunochemical characterization of this autoantibody revealed that it was IgM and belonged to the immunoconglutinin family. We have studied the effects of this autoantibody on the formation and dissociation kinetics of classical C3-convertase.

Pharmacokinetics of temocillin (BRL 17421) in subjects with normal and impaired renal function

The pharmacokinetics of temocillin were investigated in five normal subjects and in 20 uraemic patients. Normal subjects were given single intravenous doses of 3.75, 7.5 and 15 mg/kg of temocillin and a single intramuscular dose of 7.5 mg/kg. Patients with renal impairment were given 7.5 mg/kg of the antibiotic intravenously. A three-compartment open model was used to calculate kinetic data after iv administration. Pharmacokinetic parameters of temocillin were similar both for the three iv doses and for the im dose. The terminal serum half-lives (T1/2 beta) averaged 4.75-5.88 h. The central distribution volume (Vc) and the apparent volume of distribution (Vd area) were 0.093-0.111 and 0.268-0.303 l/kg, respectively. Renal and total body clearances were within 27.4-34.1 and 40.2-47.8 ml/min/1.73 m2, respectively. 67.4-71.5% of the dose was recovered unchanged in urine over 24 h. Intramuscular dosing of 7.5 mg/kg gave a mean peak level of 26.71 mg/l at 1.67 h. In uraemic patients, similar maximum serum concentrations were found after a single 7.5 mg/kg iv dose. The terminal half-life increased according to the degree of renal failure, from 5 h in normal subjects to about 30 h in severe uraemic patients. Renal impairment did not significantly modify Vd area, fractional clearance (Cr/GFR) and non renal clearance. 65.2% of the antibiotic was removed during haemodialysis. Dosage adjustments of temocillin in uraemic patients are proposed.

Pharmacokinetic aspects of guanfacine withdrawal syndrome in a hypertensive patient with chronic renal failure

The unusual observation of a withdrawal syndrome due to guanfacine in a hypertensive patient with chronic renal failure led to a study of the kinetics of the drug in this patient. The principal pharmacokinetic parameters of guanfacine were greatly altered, with extended biotransformation and a decrease in the half-life compared to the values observed in other cases of severe renal insufficiency. Associated treatment with phenobarbital had had a considerable effect, as shown by the results of a further kinetic study 2 months after withdrawal of the phenobarbital. The findings then were in good agreement with reference values which strongly suggests a consequence of the enzyme inducing effect of phenobarbital. Advice about the dosage regimen in such cases is given.

[Functional, histological, biochemical renal modifications. Comparative study of dibekacin, gentamicin, tobramycin, netilmicin and amikacin]

In this study, we evaluate the nephrotoxic potential of dibekacin (D) compared to gentamicin (G), tobramycin (T), amikacin (A) and netilmicin (N). The mean features of aminoglycoside nephrotoxicity are: a lysosomal membrane fragilization, a lysosomal phospholipidosis characterized by a decrease activity of sphingomyelinase, an increase lysosomal volume with both an increase of individual size and an increase number of lysosomes, a cell necrosis and renal failure. We have quantified these parameters biochemically and morphometrically. We can classify, considering doses and durations, the aminoglycosides as gentamicin greater than or equal to netilmicin greater than dibekacin = tobramycin greater than amikacin for decreasing nephrotoxic incidence.

[Pharmacokinetics of dibekacin in patients with chronic renal impairment]

The pharmacokinetics of dibekacin were studied in 23 patients with varying degrees of renal insufficiency. Creatinine clearance was between 4 and 51 ml/min. Chronic renal insufficiency did not affect maximum serum concentrations, nor the time required to reach a peak level after an intramuscular injection of 1 mg/kg of dibekacin. The maximum concentration was 4 to 5 mcg/ml and the peak obtained within the first hour. Renal insufficiency caused a very marked prolongation in the serum half-life of elimination. This rose from 6 hours in moderate renal insufficiency to 50 hours in a patient with a clearance of a few millilitres. Whatever the degree of renal insufficiency, it should be noted that urinary concentrations remained markedly higher than the MIC of organisms sensitive to the aminoglycoside. Dibekacin is highly dialysable, being virtually totally extracted during a 6 hours dialysis session using a membrane of 1 m2 surface area. An outline of dose adaptations in relation to the degree of renal insufficiency is suggested on the basis of these pharmacokinetic data.

The pharmacokinetics of cefotaxime and its metabolites in subjects with normal and impaired renal function

The pharmacokinetics of single doses (15 mg/kg) of cefotaxime and each of its metabolites were examined in six normal subjects and 24 patients who showed various degrees of renal insufficiency. An additional nine patients with renal failure were entered into a multiple-dose study in which cefotaxime (1 g) was given twice daily for five to seven days. After intravenous administration, the levels of cefotaxime in serum declined in two phases. The half-life for the terminal phase was 1.10 +/- 0.78 hr. Cefotaxime administered intramuscularly was well absorbed from the injection site (91% +/- 19%) and produced maximal levels of 25.5 +/- 3.5 microgram/ml in serum at approximately 0.5 hr after injection. The levels of the desacetyl metabolite in serum were comparatively low, and the half-life of this metabolite was 1.3 hr. Microbiologic measurements of cefotaxime showed that the half-life of the drug was lower in normal subjects (1.71 +/- 0.90 hr) than in patients with severe renal impairment (half-life, 10.20 +/- 3.43 hr). However, this difference was due primarily to desacetylcefotaxime. Specific measurement by high-performance liquid chromatography indicated only a slight increase in the half-life of cefotaxime, whereas the increase in half-life of desacetylcefotaxime was greater. The most pronounced increases in half-life of metabolites occurred when values for creatinine clearance in patients were below about 5 ml/min per 1.73 m2. When cefotaxime was administered repetitively, the ratio of maximal serum levels after the last dose to those after the first dose demonstrated minimal accumulation of intact drug. The average accumulation of desacetylcefotaxime in this group of patients was about twofold, and that for metabolites M2 and M3 was approximately fourfold. This accumulation of metabolites was observed only in those patients with severe renal impairment and was not excessive. Hemodialysis caused a significant reduction in the half-life of both cefotaxime and desacetylcefotaxime. Recommendations are made for the adjustment of dosing schedules in patients with renal failure.

[Pharmacokinetics of cefotaxime and metabolites in uremic patients (author's transl)]

The study was done after a single dose in 6 normal subjects and 24 patients with varying degrees of renal insufficiency. In normal subjects, the results are similar whatever the assays are used. In uremic patients, the half-life for the terminal phase increased with renal failure with the microbioassay, but it is demonstrated that deacetyl cefotaxime has only a prolonged half - life with a more specific assay = HPLC method. After repetitive doses, the tendency for accumulation was only noted in patients with very severe renal failure (creatinine clearance less than 5 ml.min-1).