Pharmacokinetics of single daily dose gentamicin in children with cancer.

PURPOSE: To study the pharmacokinetics of single daily dose (SDD) gentamicin in children with cancer. METHODS: Serum concentrations of gentamicin were prospectively measured at 0.5, 8, 16, and 24 hours after a single daily dose of gentamicin 6 mg/kg, given as a 30-minute infusion in 18 febrile children with cancer and a central venous catheter. Then the peak (0.5-hour) and 12-hour serum concentrations of gentamicin were prospectively measured after a SDD of 7 mg/kg during 73 febrile episodes in 54 pediatric cancer patients with suspected infections. The aim was to achieve a peak serum concentration of 15 to 20 microg/mL 10 times the minimum inhibitory concentration (MIC) for sensitive Pseudomonas strains, resulting in good bactericidal activity and a long post-antibiotic effect (PAE) after a SDD of gentamicin. RESULTS: The mean serum peak gentamicin concentration 30 minutes after the end of the infusion of 6 mg/kg was 13.3 +/- 4.0 microg/mL. The mean serum concentration 16 hours after the infusion was 0.3 +/- 0.2 microg/mL. The mean peak and 12-hour serum concentration after SDD of 7 mg/kg was 17.2 +/- 3.9 microg/mL and 0.9 +/- 0.7 microg/mL, respectively. The mean peak serum concentration after SDD of 7 mg/kg in children younger than 5 years of age (16.1 +/- 3.5 microg/mL ) was significantly lower than that of children over 5 years of age (18.2 +/- 3.9 microg/mL; P = 0.02). The desired peak serum concentration was achieved in 67% of children younger and 84% of those older than 5 years of age. CONCLUSION: Adequate peak serum concentrations of gentamicin in children may be obtained with a SDD of 7 mg/kg. Children younger than 5 years of age achieve lower peak serum gentamicin concentration after SDD of 7 mg/kg than those older than 5 years.     

Pharmacokinetic analysis of the disposition of intravenous theophylline in young children.

The disposition of a single intravenous dose of theophylline, 3.2 mg/kg, was studied using a high-pressure liquid chromatographic assay in ten asthmatic children one to four years of age. The man plasma theophylline clearance was 0.100 +/- 0.036 l/kg/hr, kel 0.49 +/- 0.30 hr-1, betat1/2 3.38 +/- 1.11 hr, alphat1/2 0.13 +/- 0.09 hr, and V1 0.25 +/- 0.13 1/kg. Plasma theophylline clearance was approximately 40% greater in these children than that reported in adults, mainly due to an increased rate of drug elimination. Large interindividual differences were observed. Analysis of data using either a two- or one-compartment model yielded almost identical dosage regimens designed to rapidly achieve and maintain a chosen plasma theophylline concentration. Calculations based upon mean values of pharmacokinetic constants predict that a maintenance dose rate for aminophylline of 30 mg/kg/day, after a loading dose of 5.6 mg/kg, would rapidly achieve and maintain a mean steady-state plasma concentration of theophylline of 10 mg/1. Potential toxicity of such a regimen has not been excluded, since therapeutic trials (with achievement of steady state) have not yet been conducted.     

Prevention of apnea and bradycardia in low-birthweight infants.

The efficacy of theophylline in preventing severe apnea was evaluated in 17 low-birthweight infants (mean weight, 1,400 gm). Apnea was detected and accurately quantified by 13-hour pneumogram recordings and correlated with serum theophylline levels. Nursing observations coupled with on-line alarm systems detected only 39% of severe apneic episodes as compared to the pneumogram recording technique. Theophylline in six hourly oral doses(1.5 to 4.0 mg/kg) yielded two-hour serum concentrations of 6.6 to 11.0 mug/ml which completely controlled apneic spells exceeding 20 seconds in duration and markedly reduced 10- 19-second apneic episodes and any resultant bradycardia. At these serum levels, toxicity was not observed. Therapy with theophylline should be instituted at a dose of 2 to 3 mg/kg every six hours and the optimum therapeutic dose should be individualized as determined by objective quantitation of apnea and serum theophylline concentration.     

Evaluation of a netilmicin-loading dose in very low birthweight infants

BACKGROUND: The bactericidal efficacy of aminoglycosides is directly related to maximum serum concentrations, particularly the initial one. Therefore, several groups have recommended an aminoglycoside loading dose. Our goal was to develop a simplified dosage regimen for preterm infants which would result in therapeutic maximum serum concentrations early in the course of therapy. METHODS: Open, noncomparative study during November 2000 to April 2001. The modified netilmicin-dosing protocol included a loading dose of 5 mg/kg in the first week of life, followed by a maintenance regimen of 3.5 mg/kg every 24 h. After the first week of life the corresponding doses were 6 (loading) and 5 mg/kg (maintenance). A peak level was measured 30 min after the second dose, and a trough level immediately before the third dose. RESULTS: Thirty-five very low birthweight infants (mean birthweight 876 +/- 170, range 536-1,385 g; mean gestational age 26 +/- 1.8, range 23-30 weeks) who had 46 episodes of netilmicin treatment were included in the analysis. Mean netilmicin peak and trough values were 15.9 +/- 3.7 (range 8.9-28.9) and 3.4 +/- 1.3 (range 1.0-7.8) micromol/l, respectively. Ninety-one percent of all peak levels were within the targeted range of > or =10 micromol/l. Eleven trough values (24%) were > or =4 micromol/l: in 7 instances netilmicin was administered within the first week of life, 5 of these patients had concomitant indomethacin treatment. Only 1 of the 35 neonates had a rise in serum creatinine of > or =0.5 mg/dl during netilmicin therapy. Hearing evaluations were performed in 25 of the 29 surviving infants at discharge home, all of which gave normal results. CONCLUSIONS: The new netilmicin-dosing protocol yielded therapeutic maximum serum concentrations in 91% of cases after the second dose. However, a significant number of very low birthweight infants had elevated trough levels, particularly when netilmicin was administered in the first week of life with concomitant indomethacin treatment. We speculate that a longer interval between the loading dose and the first maintenance dose would result in fewer elevated trough levels with a similarly high number of therapeutic peak levels.     

Dosage schedule for intravenous aminophylline in apnoea of prematurity, based on pharmacokinetic studies.

15 preterm infants were treated for recurrent apnoea with theophylline. 5 were given oral choline theophyllinate, but this was erratically absorbed. 14 were given IV aminophylline on 23 occasions. Apparent volume of distribution of theophylline in 12 infants was 0.71 +/- 0.18 1/kg (mean +/- SD). Plasma clearance rate measured in 11 infants at steady state was 18.6 +/- 4.8 ml/kg per hour. Calculations show that a loading dose of 6.2 mg/kg aminophylline intravenously and maintenance of 4.4 mg/kg per day would produce serum levels of between 6 and 12 mg/l in all but one of the infants studied, with no infant having toxic levels.     

Individualizing gentamicin dosage in patients with cystic fibrosis: limitations to pharmacokinetic approach

Gentamicin serum concentrations were measured in 15 children and seven adults with cystic fibrosis and in eight children with other diseases. Potentially toxic trough concentrations occurred in three of the first nine patients studied, in whom the dose and a 4-hour dosing interval were prescribed on the basis of one-compartment pharmacokinetic calculations (Sawchuck-Zaske method). In contrast, final concentrations were within the accepted target ranges for the remaining 13 patients with cystic fibrosis, in whom the dose and interval were adjusted empirically on the basis of a single pair of "peak" and trough values. The mean +/- SD final dosage required to achieve target concentrations was 13.8 +/- 2.9 mg/kg/d for children and 11.8 +/- 1.1 mg/kg/d for adults (P greater than 0.05), generally divided into four doses at 6-hour intervals. Mean half-life and incremental increase in serum concentration from previous trough to subsequent "peak," an indirect measurement of volume of distribution, were not significantly different between children or adults with cystic fibrosis and pediatric control subjects; there was little interpatient variability in these values. Thus the high dosage requirements were related more to the higher target concentrations than to altered pharmacokinetic disposition in patients with cystic fibrosis. We conclude that the initial dose of gentamicin to achieve a peak of 8 to 12 micrograms/mL and a trough of less than 2.0 micrograms/mL in patients with cystic fibrosis should be 3 mg/kg administered every 6 hours in children and every eight hours in adults. Subsequent dosage adjustment should be made on the basis of a pair of peak and trough serum concentration measurements obtained after the fifth dose. Dosing intervals in this patient population generally should be no shorter than every 6 hours, even if the initial trough concentration is less than 1 microgram/mL.     

Pharmacokinetics of enprofylline administered intravenously and as a sustained-release tablet at steady state in children with asthma

The pharmacokinetics of enprofylline (3-propylxanthine) were studied in 10 children with asthma (mean age 7.9 years), after enprofylline 1 mg/kg given intravenously and after enprofylline 7.5 +/- 1.3 mg/kg given as a sustained-release tablet after 8 days of oral dosing twice daily. The mean +/- SD enprofylline serum elimination half-life was 1.06 +/- 0.20 hours, considerably shorter than the half-life reported in adults. The mean steady-state volume of distribution was 0.55 +/- 0.05 L/kg. The mean clearance rate was 0.44 +/- 0.06 L/hr/kg. The mean enprofylline serum concentration at steady state was 1.7 +/- 0.5 mg/L. The mean peak to trough ratio was 3.02 +/- 1.31. On the first and ninth study days, 87% +/- 8% and 90% +/- 16%, respectively, of the dose of enprofylline was recovered as unchanged drug in the urine. Enprofylline has a short half-life in children, but the sustained-release formulation provides stable serum concentrations and satisfactory relief of asthma throughout the 12-hour dosing interval.     

Pharmacokinetic profile of caffeine in the premature newborn infant with apnea.

The pharmacokinetic profile of caffeine was studied in 32 premature newborn infants with apnea: 12 following a single intravenous dose; 3 after a single oral dose; 7 during treatment with an initial empirical (high) maintenance dose schedule; and 10 during treatment with a revised (lower) dose schedule. Mean (+/- SE) AV d, t 1/2, ke1, and clearance following a single intravenous dose were 0.916 +/- 0.070 1/kg, 102.9 +/- 17.9 hours, 0.009 +/- 0.001/hours and 8.9 +/- 1.5 ml/kg/hour, respectively. Rapid absorption was noted with plasma concentrations of 6 to 10 mg/l achieved within 30 minutes to two hours following an oral dose of 10 mg/kg. Cpss of caffeine in infants given a high empirical dose (11.2 +/- 1.5 mg/kg/day) ranged from 22.5 to 84.2 mg/l (mean = 45.3) whereas a dose schedule based on kinetic data (2.5 mg/kg/day) yielded plasma concentrations ranging from 7.4 to 19.4 mg/l (mean = 13.7). We suggest a loading dose of 10 mg/kg intravenously or orally followed by a daily maintenance dose of 2.5 mg/kg/day administered as a single dose for the treatment and prevention of neonatal apnea.     

Pharmacokinetics and antipruritic effects of hydroxyzine in children with atopic dermatitis

We studied the pharmacokinetics and antipruritic effects of hydroxyzine hydrochloride in 12 children, mean age 6.1 +/- 4.6 years, with severe atopic dermatitis. After a single 0.7 mg/kg orally administered dose of the drug, the mean peak serum hydroxyzine concentration of 47.4 +/- 17.3 ng/ml occurred at a mean time of 2.0 +/- 0.9 hours. The mean elimination half-life was 7.1 +/- 2.3 hours, the mean clearance rate was 32.08 +/- 11.05 ml/min/kg, and the mean apparent volume of distribution was 18.5 +/- 8.6 L/kg. The elimination half-life increased with increasing age (r = 0.83). Pruritus was significantly suppressed from 1 to 24 hours after the administration of the dose, with greater than 85% suppression from 2 to 12 hours. The only adverse effect reported was sedation. In a subsequent double-blind, crossover, multiple-dose study of 2 weeks' duration, hydroxyzine 0.7 mg/kg three times daily was as effective as hydroxyzine 1.4 mg/kg three times daily in relieving pruritus and promoting resolution of the skin lesions. The 0.7 mg/kg tid dose caused significantly less sedation than the 1.4 mg/kg tid dose.     

Sustained-release terbutaline vs sustained-release theophylline in young patients with asthma

Twenty patients with asthma (mean age, 10.9 +/- 2 years) entered a six-week, randomized, double-blind, crossover comparison of sustained-release (S-R) terbutaline sulfate (Bricanyl Durules) vs S-R theophylline (Theo-Dur). In each two-week study period each patient received S-R theophylline twice daily in doses previously adjusted to give serum theophylline concentrations in the range of 10 to 20 mg/L (56 to 111 mumol/L); or S-R terbutaline sulfate, 5 mg twice daily; or S-R terbutaline sulfate, 7.5 mg twice daily. All treatment regimens produced significant improvement in one or more pulmonary function test values compared with prestudy values. The incidence of acute asthma episodes were similar during each treatment regimen. No clinically significant difference occurred between the regimens for daily symptom scores, peak expiratory flow rates, or use of a terbutaline metered-dose inhaler. At the end of the theophylline treatment period, the mean (+/- SD) theophylline level 12 to 14 hours after the last dose was 10.1 +/- 3.3 mg/L (56 +/- 18 mumol/L); at the end of the terbutaline treatment periods, the mean trough terbutaline levels were 2.22 micrograms/L (9.9 +/- 4.4 nmol/L) (S-R terbutaline sulfate, 5 mg twice daily) and 3.07 micrograms/L (13.7 +/- 5.4 nmol/L) (S-R terbutaline sulfate, 7.5 mg twice daily). Adverse effects, including tremor, occurred with similar frequency during all three drug regimens. Sustained-release formulations of theophylline and terbutaline, in the dosages studied, provided comparable control of asthma symptoms.     

Serum concentrations of theophylline in children following the administration of doses generally recommended: new dosage regimen required.

Serum concentrations of theophylline following intravenous and oral administration of aminophylline were studied in asthmatic children, 2--17 years of age. The biological half-life (t 1/2 beta) of theophylline varied between 165 and 495 min. The results revealed that an intravenous loading dose of 6 mg of aminophylline per kg body weight was necessary in order to obtain therapeutic concentrations in children who had not received the drug for the last 6 to 8 hours. The maintenance dose should be determined and controlled by use of serum concentration determinations. In a group of children receiving 5 mg of aminophylline per kg body weight 3 times a day orally, none had concentrations within the therapeutic range in the morning, and only 39% reached therapeutic levels 2 h after the morning dose. No correlation was found between the serum concentration of theophylline and the amount of drug given per kg body weight. The results show that theophylline concentration analysis is necessary to obtain adequate therapeutic levels in children without risking toxic effects.     

Safety and pharmacokinetics of fluconazole in children with neoplastic diseases

To evaluate the safety, tolerance, and pharmacokinetics of fluconazole in children with neoplastic diseases, we studied fluconazole in 26 children, aged 5 to 15 years, with normal renal function who were receiving treatment for cancer. The patients received fluconazole, 2, 4, or 8 mg/kg per day for 7 days intravenously for a 2-hour period. Patients had no nausea or vomiting related to fluconazole; three patients had an asymptomatic rise in hepatic aminotransferase values after four to six doses (one patient at 2 mg/kg per day and two patients at 8 mg/kg per day), which returned to normal within 2 weeks after discontinuation of the drug. Fluconazole showed linear first-order kinetics over the dosage range tested and during multiple dosing. After the first dose, mean clearance was 22.8 +/- 2.3 ml/min, volume of distribution 0.87 +/- 0.06 L/kg, and terminal elimination half-life 16.8 +/- 1.1 hours. Similarly, after the last dose, clearance was 19.4 +/- 1.3 ml/min, volume of distribution 0.84 +/- 0.04 L/kg, and terminal elimination half-life 18.1 +/- 1.2 hours. Patients receiving their first fluconazole dose of 8 mg/kg achieved peak serum levels of 9.5 +/- 0.4 microgram/ml and trough levels of 2.7 +/- 0.5 microgram/ml 24 hours later, and an area under the serum concentration-time curve from time zero to infinity of 186 +/- 16 micrograms.hr per milliliter. Renal clearance of fluconazole was 65% +/- 5% of total clearance and demonstrated the predominantly renal excretion of this drug. We suggest that the shorter serum half-life and the higher frequency of aminotransferase elevations in comparison with those of adults warrant careful investigation of fluconazole in controlled clinical trials.     

Sustained-release theophylline preparations in asthmatic children. A short-term comparison of two products and the relationship of serum theophylline levels and pulmonary function changes

In a four-week study, 20 children with chronic asthma were treated in a randomized, double-blind, crossover manner with two sustained-release theophylline preparations (Theo-Dur and Uniphyl) to compare their drug concentrations and clinical efficacy. In addition, the effects of serum theophylline concentration on results of pulmonary function tests (PFTs) were evaluated. Twelve-hour doses (to achieve serum concentrations between 10 and 20 mg/L) of each drug were given for two weeks. Diaries of asthma symptoms and peak flows were kept daily. After 14 days of each treatment, children returned for measurement of theophylline levels and PFTs over a 12-hour period. The two drugs were equally effective in clinically controlling asthma over the two weeks of treatment. Serum theophylline levels obtained over the 12-hour dosing periods were not significantly different. Uniphyl provided less (but not significantly) deviation between peak and trough levels. Analysis of individual patient data did not reveal a predictable relationship between serum theophylline concentrations and results of PFTs.     

Oral theophylline dosage for the management of chronic asthma

Theophylline dosage requirements to maintain serum concentrations of 10 to 20 microgram/ml among asthmatic patients were examined in 156 children, ages 2 1/2 months to 16 years, and 33 otherwise health adults. Using 100% bioavailable preparations, low doses were used initially and increased, if tolerated, at three-day intervals. Final dosage was based on serum theophylline measurements which were subsequently repeated after six or more months of therapy. Dosage standardized by weight averaged 24.1 +/- 5.5 mg/kg/day (mean +/- SD) among the 77 children under age 9 years. Age-related variability of weight-adjusted doses were not observed for younger children, but average dose requirements decreased progressively beyound age 9 years to 13 mg/kg/day for patients beyoung 16 years of age. Although interpatient variability in dosage was confirmed at all ages, intrapatient variability in requirements over an average eight-month interval were small; dosage changes to maintain therapeutic serum concentration were primarily associated with growth. These data allow age-specific guidelines for dosage recommendations based on the likelihood of optimally effective and potentially toxic serum theophylline concentrations.     

Bioavailability of a slow-release theophylline capsule given twice daily to preschool children with chronic asthma: comparison with liquid theophylline

The reliability of slow-release theophylline products in young children has been questioned. Therefore, we studied the bioavailability of a commonly prescribed slow-release theophylline formulation (Slo-Bid Gyrocaps), administered twice daily by sprinkling the beads on applesauce. Serial measurements of serum theophylline concentrations were obtained during steady state in eight children (ages 1.6 to 5 years) after receiving a reference liquid theophylline product every six hours and also while receiving the slow-release product every 12 hours. The morning dose of slow-release theophylline was given before the child had eaten, and the evening dose was given two hours after supper. The extent of absorption of the slow-release product was 98.3 +/- 20.2% (mean +/- SD) relative to the liquid reference. The serum concentration fluctuations, expressed as percentage of the measured trough, did not differ between the two products: 108 +/- 59% v 129 +/- 97% (P greater than .05) for reference and slow-release products, respectively. Three of the eight patients had unacceptably large fluctuations (greater than 100%) while receiving the slow-release regimen, and two of these three had unacceptable fluctuations while receiving the liquid reference. The rate of absorption was slower after the evening dose of slow-release product (postprandial), resulting in significantly smaller fluctuations, and lower peak concentrations. Time to peak concentration while receiving the slow-release regimen varied from two to four hours after the evening dose and from two to eight hours after the morning dose. However, the average difference between the peak concentration and the four-hour measurement after the morning dose was only 0.3 microgram/mL (range 0 to 2.6 micrograms/mL).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of a scheme for establishing and maintaining dosage of theophylline in ambulatory patients with chronic asthma

To assess the utility of a dose-titration scheme for determining maintenance theophylline requirements, dose requirements and stability of serum concentrations were examined using 3537 serum determinations from 1073 patients with chronic asthma during a 5-year period. When the dosing scheme was followed, 78% of initial serum concentrations were within the target range of 10 to 20 micrograms/ml; the mean number of measurements to attain this range was 1.3. Among 404 of these patients prospectively questioned, adverse effects were not present in all 41 whose initial serum concentration was less than 10 micrograms/ml, occurred in eight of 296 patients when serum concentrations were between 10 and 20 micrograms/ml, and were present in 21 of 67 when concentrations were greater than 20 micrograms/ml. After final dose adjustment, mean dose requirements among those who attained serum concentrations of 10 to 20 micrograms/ml averaged 22 mg/kg/day in 1- to 9-year-old children, 20 mg/kg/day in 9- to 12-year-old children, 18 mg/kg/day in 12- to 16 year-old children, and 13 mg/kg/day in the 94 patients older than 16 years of age. Repeat serum concentrations after 3 months to 2 years showed 66% remaining within the 10 to 20 micrograms/ml range and another 15% between 7.5 and 10 micrograms/ml; 9% were greater than 20 micrograms/ml, and none greater than 30 micrograms/ml. Thus the dosing scheme produces serum concentrations in the usual therapeutic range with a minimum of samples and few side effects; most patients maintained acceptably stable blood levels.     

Sulfapyridine metabolites in children with inflammatory bowel disease receiving sulfasalazine.

Fifteen children followed as outpatients with chronic inflammatory disease of the colon were given sulfasalazine in doses from 1 to 4 gm/day (22 to 68 mg/kg, or 0.69 to 2.33 gm/m2). No correlation was found between the dose/m2 administered and the total serum sulfapyridine levels. However, 11 of 15 patients achieved SP levels greater than or equal to 17 micrograms/ml, a level approximating that reputedly associated with therapeutic efficacy. Patients who were either slow acetylators or slow hydroxylators of sulfapyridine had total SP levels significantly higher than patients who were both rapid acetylators and hydroxylators (20.0 +/- 1.2 vs 14.6 +/- 1.6). Total SP serum levels were not correlated with the activity of the disease. No toxic levels (greater than 50 micrograms/ml of SP) were encountered. We conclude that a dose of SASP in the range of 1.5 to 2.0 gm/m2 can be safely administered to children and is usually associated with serum SP levels considered in the therapeutic range. Although one-third of children are both rapid acetylators and hydroxylators and will have somewhat lower SP levels, the routine monitoring of SASP therapy with SP levels is not necessary for management of disease.     

Pharmacokinetics and metabolism of rectally administered paracetamol in preterm neonates.

AIM: To investigate the pharmacokinetics, metabolism, and dose-response relation of a single rectal dose of paracetamol in preterm infants in two different age groups. METHODS: Preterm infants stratified by gestational age groups 28-32 weeks (group 1) and 32-36 weeks (group 2) undergoing painful procedures were included in this study. Pain was assessed using a modified facies pain score. RESULTS: Twenty one infants in group 1 and seven in group 2 were given a single rectal dose of 20 mg/kg body weight. Therapeutic concentrations were reached in 16/21 and 1/7 infants in groups 1 and 2, respectively. Peak serum concentrations were significantly higher in group 1. Median time to reach peak concentrations was similar in the two groups. As serum concentration was still in the therapeutic range for some infants in group 1, elimination half life (T1/2) could not be determined in all infants: T1/2 was 11.0 +/- 5.7 in 11 infants in group 1 and 4.8 +/- 1.2 hours in group 2. Urinary excretion was mainly as paracetamol sulphate. The glucuronide:sulphate ratio was 0.12 +/- 0.09 (group 1) and 0.28 +/- 0.35 (group 2). The pain score did not correlate with therapeutic concentrations. CONCLUSIONS: A 20 mg/kg single dose of paracetamol can be safely given to preterm infants in whom sulphation is the major pathway of excretion. Multiple doses in 28-32 week old neonates would require an interval of more than 8 hours to prevent progressively increasing serum concentrations.     

Pharmacokinetics of quinine in children

Serum quinine concentrations were measured in seven children after intravenous infusion of quinine dihydrochloride, in eight children after intramuscular injection of quinine dihydrochloride, and in six children after nasogastric administration of a solution of quinine dihydrochloride. The mean (+/- SD) half-life of quinine was 11.1 +/- 4.8 hours, and the volume of distribution was 1.39 +/- 0.37 L/kg. To attain a serum level of 10 microgram/ml quinine, we suggest that children with severe malaria be given a loading dose of 20 mg/kg quinine dihydrochloride parenterally, followed by 7.5 mg/kg every 8 hours. Once recovery begins, quinine sulphate 10 mg/kg may be given orally every 8 hours. Serum concentrations should be monitored, if possible, because they vary greatly from person to person. Quinine is rapidly and completely absorbed after either intramuscular or nasogastric administration.     

Age-dependent dose response to gentamicin.

Serum gentamicin concentrations were measured 30 minutes after 140 intravenous doses in 60 children and nine adults with normal renal function. Distinct interpatient variation was observed but individual patients tended to have similar pharmacokinetics with repeated doses. Age had a significant effect in that mean peak serum concentrations were 1.58 mug/ml per 1 mg/kg dose in children between 6 months and 5 years, 2.03 mug/ml per 1 mg/kg in those between 5 and 10, and 2.86 mug/ml per 1 mg/kg in children 10 to 15 years of age. The mean calculated single dose of gentamicin necessary to achieve a peak serum concentration between 4 and 5 mug/ml is 2.5 mg/kg for ages 0.5 to 5 years, 2.0 mg/kg for ages 5 to 10 years, and 1.5 mg/kg for individuals over 10 years of age.