Aminoglycosides, among the most commonly used antibiotics in neonates, have frequently been implicated in nephrotoxic reaction. Studies in adults have indicated that phospholipiduria (PLU) is rapidly increased during aminoglycoside therapy, in relation to the renal phospholipidosis these drugs are known to induce in renal cortex. We studied the effect of amikacin (AK) on PLU in male prematurely-born neonates (gestational age > 34 weeks; postnatal age < or = 2 days) by assessing the urinary excretion of 4 enzymes (N-acetyl-beta-D-glucosaminidase [NAG], alkaline phosphatase, tau-glutamyltransferase and alanine aminopeptidase) and 4 low-molecular-weight proteins (beta-2-microglobulin, clara cell protein, microalbumin and retinol-binding protein) which are currently used to monitor the development and extent of renal tubular damage. Twenty-two patients and 8 healthy (as control) neonates were enrolled in the study. Patients were treated with AK (15 mg/kg per day) given in one (qd, n = 10) or two equal injections (b.i.d., n = 12) for durations of 7-11 days. PLU and proteinuria were determined in 24-h urine sample collections, and enzymes were assessed in spot urine collected at 9 a.m. We found that in neonates, AK causes a significant increase in PLU, and in enzymuria except for NAG in the qd group. Proteinuria showed no significant change due to AK treatment. No significant differences were observed between qd and b.i.d. administrations of AK for all parameters tested. We conclude that PLU could be used in neonates as well as in adults as a non-invasive method to monitor the development of the renal phospholipidosis during aminoglycoside therapy.

Neonates, especially preterms, are known to have low glomerular filtration rates (GFR). This may result in elevated trough concentrations during multiple administration of aminoglycosides (AGs), potentially leading to nephro- and ototoxic reactions. The once-daily administration (q.d.) of AGs has been shown to be equally or better tolerated in adults and children than the conventional schedules (twice daily, b.i.d.; thrice daily, t.i.d.), while offering potential pharmacodynamic and nursing advantages. No data, however, are available for neonates. As a consequence, this pilot study was conducted in order to assess the tolerance of the once-a-day administration of amikacin in comparison with the twice daily dose regimen, in relation to the pharmacokinetics of the drug under these two schedules. 22 Male neonates (gestational age > or = 34 weeks; postnatal age < or = 2 days) were randomized to receive amikacin (AK) (15 mg/kg/day) q.d. (n = 10) or b.i.d. (n = 12) together with ampicillin (50 mg/kg/12 h). AK plasma levels were measured at days 1, 3, 5 and 7 of treatment just before the next dose (trough level) and 1 h after completion of infusion (peak level) and after 3 and 6 h only at day 1. Due to the small size of the samples, no difference in efficacy could be assessed and was not the aim per se. Glomerular dysfunction was assessed by creatinine clearance, and tubular injuries by the urinary excretion of proteins (retinol binding protein, beta 2-microglobulin, clara cell protein (P1) and microalbumin), enzymes (N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, alanine aminopeptidase, and gamma-glutamyltransferase), and total phospholipids (TPL) in urine. Ototoxicity was assessed by brainstem auditory evoked potentials (BAEPs) at days 0, 3 and 9 of therapy. Eight healthy neonates served as controls. All patients showed a normal and similar increase of GFR during the first postnatal days. Proteinuria did not increase, but enzymuria and TPL increased significantly during the treatment in both AK groups without significant difference between groups. BAEPs at day 9 were not significantly different between treated and untreated patients. We conclude from this pilot study that, in the absence of more toxicity, the q.d. administration of AK in neonates of > or = 34 weeks of gestational age may be recommended over its bid schedule in view of its potential advantages.

Coadministration of poly-L-aspartic acid (poly-L-Asp) protects rats against all measured signs of aminoglycoside nephrotoxicity. Based on in vitro and acute in vivo models, previously we hypothesized that poly-L-Asp protects by forming complexes with the drug in lysomes of proximal tubular cells. However, another closely related peptide, poly-L-glutamic acid (poly-L-Glu), could not protect against gentamicin-induced phospholipidosis and nephrotoxicity, presumably because it is susceptible to rapid hydrolysis in sysosomes in vivo. The present study expands the in vivo comparison between these two polyanions to a subacute model of rats and examines in detail the influence of these polymers on the qualitative and quantitative morphological alterations of lysosomes, phospholipiduria and proliferation of cortical cells induced by gentamicin. Our results not only demonstrated that despite a significantly higher drug cortical accumulation, the coadministration of poly-L-Asp almost completely protects against the development of all these early renal alteration but also pointed to the possibility of a mild, albeit apparently nonlethal, lysosomal thesaurismosis to develop under these conditions. In contrast, poly-L-Glu could not protect against these early renal alterations, though cortical drug accumulation was not significantly higher; however, it induced a conspicuous proliferation of peritubular interstitial cells. Therefore, the present work, taken together with the earlier results of ours as well as that of others, tends to strengthen the hypothesis that the site of action of poly-L-Asp must be in lysosomes, which are also the organelles that sequester and accumulate the drug.

The optimal management of fever in granulocytopenic patients remains controversial. This pilot study investigated the potential value of single daily doses of amikacin administered empirically with ceftriaxone in febrile granulocytopenic patients. None of the patients died as a result of infection or toxicity from the prescribed regimen. Serum concentrations failed to show drug accumulation. Modifications of empirical antimicrobial therapy were made at a similar rate to other conventional regimens. Vancomycin seemed to increase the incidence of nephrotoxicity. Overall, this pilot study suggests that empirical therapy with single daily doses of amikacin plus ceftriaxone is safe and effective and should be further investigated in a larger number of patients.

The pharmacologic parameters and toxicity of netilmicin (6 mg/kg/day) given once daily (qd) or thrice daily (tid) for the treatment of urinary tract infections were studied in a randomized prospective study of 60 cancer patients. The overall efficacy was 96%. Nephrotoxicity, assessed by the measure of urinary excretion of phospholipids, was lower for the patients receiving the qd regimen than for those receiving the tid regimen. Elevation of serum creatinine (20% over baseline) occurred in one patient receiving the qd regimen and in three receiving the tid regimen. Cochleotoxicity, assessed by pure-tone audiometry (250 to 18,000 Hz) occurred in one patient receiving the qd regimen and none receiving the tid regimen. Concentrations in sera were measured on days 1 and 5. No significant accumulation was observed in either group. Median serum bactericidal titers, expressed as reciprocal values (percentage of the sera with a titer greater than or equal to 8), were measured against 25 test organisms in samples collected 6 h after the administration of netilmicin and were, for the qd group, 16 (82%) against members of the family Enterobacteriaceae and less than 2 (8%) against Pseudomonas aeruginosa, and for the tid group, 4 (57%) against members of the Enterobacteriaceae and less than 2 (0%) against P. aeruginosa. The rate of killing in serum was rapid (2 to 3 log in 2 h against P. aeruginosa; 3 to 5 log in 2 h against members of the Enterobacteriaceae) and correlated with the sampling time and hence the concentration in serum of netilmicin. The duration of the postantibiotic effect in serum depended also on the strain and the sampling time of the serum.

Administration of the aminoglycoside antibiotic, gentamicin, even at therapeutic doses, causes renal lysosomal phospholipidosis. We now report that protein- and lipid-bound sialic acid levels are increased significantly in a time-dependent fashion in the renal cortex of rats injected with gentamicin (10 mgkg body wt. per day) for 4–10 days and a significant relationship could be observed between these two parameters. This elevation was not due to tissue regeneration, since it was not observed in cisplatin-treated animals.

The safety, pharmacokinetics and efficacy of one daily injection (qd) of amikacin (AK) and netilmicin (NT) was compared with the recommended schedules (cs), i.e. twice-daily or thrice-daily, respectively. Women (17-43 years, n = 78) suffering from pelvic inflammatory disease were randomly assigned to qd or cs of either AK (14 mg/kg per day) or NT (6.6 mg/kg per day). Biometric parameters were similar in the 4 groups and all patients received ampicillin (4 g/day) and tinidazole (0.8 g/day). The Repeated Measures Analysis of Variance was used to distinguish the effects of the schedules and of the drugs choice on critical parameters. Efficacy was similar in the 4 groups and not influenced by the schedule of administration. No significant differences in nephro- and oto-toxicity were observed as assessed by serum creatinine and losses of hearing at low frequencies, but early phospholipiduria and auditory losses at high frequencies were significantly reduced with the qd administration compared to cs and by AK compared to NT. These data suggest that the qd schedule of AK and of NT is as efficacious as their cs schedules, and causes less renal and auditory alterations.

Lysosomal phospholipidosis of proximal tubular cells is an early index of aminoglycoside-induced nephrotoxicity and has been documented both biochemically and morphometrically in animals and humans treated with therapeutic doses of these antibiotics (see Laurent and Tulkens 1987, for review). The various aminoglycosides differ in their capacity to induce this alteration (Laurent et al 1982; De Broe et al 1984) and amikacin, in particular, induces considerably less changes than netilmicin (Tulkens et al 1983; De Broe et al 1983). In animals, aminoglycoside administration is also associated with a marked increase of phospholipiduria (Ibrahim and Tulkens 1986; Josepovitz et al 1986). The purpose of present study was to examine phospholipiduria in humans and to compare the effect of amikacin and netilmicin in this respect.