Adolescent occupational toxic exposures: a national study.

BACKGROUND: While many previous studies describe workplace-associated injuries in adolescents, few focus on toxic exposures. Such incidents are unlikely to be reported to either federal or state agencies. However, poison control centers often get called about these poisonings and might serve as a resource for monitoring their occurrence. OBJECTIVE: To describe the frequency and severity of job-related toxic exposures involving adolescents, the specific toxic agents involved, and trends over time. METHODS: Occupational toxic exposures occurring in the United States between 1993 and 1997 were analyzed using the Toxic Exposure Surveillance System database compiled by the American Association of Poison Control Centers. Contingency tables with the chi(2) statistic were used to test bivariate associations. Logistic regression was performed to investigate trends over time. RESULTS: Of 301 228 workplace toxic exposures reported over 5 years, 8779 (3%) involved adolescents younger than 18 years. The most common agents involved were alkaline corrosives (13.2%), gases and fumes (12.0%), cleaning agents (9.7%), bleaches (8.3%), drugs (7.4%), acids (7.2%), and hydrocarbons (6.9%). The injuries were rated as severe in 14.2% of exposures, life-threatening in 0.3%, and there were 2 deaths. The proportionate frequency of occupational exposures occurring among adolescents vs adults increased over time (odds ratio, 1.003; P<.001). CONCLUSIONS: Adolescent occupational toxic exposures are an underrecognized hazard in the United States. Poison control center experience can be used to fill a gap in the surveillance of such injuries.

Invasive group A streptococcal infection and nonsteroidal antiinflammatory drug use among children with primary varicella.

OBJECTIONS: To test the hypothesis that nonsteroidal antiinflammatory drug use increases the risk of necrotizing soft tissue infections and, secondarily, all invasive group A streptococcal (GAS) infections in children with primary varicella infection. METHODS: We conducted a prospective, multicenter case-control study among children <19 years old. Cases were children hospitalized with primary varicella complicated by invasive GAS infection or necrotizing soft tissue infection identified by a network of 45 pediatric infectious disease specialists located throughout the United States. Controls were children with uncomplicated primary varicella residing in the same communities as the cases. Data on medical history, clinical features of the varicella infection, signs and symptoms of infectious complications, and medication use were collected by structured telephone interviews. Univariate and multivariate matched odds ratios were calculated using conditional logistic regression. RESULTS: Between June 1996 and September 1998, 52 cases of invasive GAS infection, including 21 with necrotizing soft tissue infection, and 172 controls with uncomplicated primary varicella were enrolled. Risk of invasive GAS infection was increased among children who were nonwhite (multivariate odds ratio [OR] 3.8, 95% confidence interval [CI]: 1.4-11), living in low-income households (OR 5.1, 95% CI: 1.7-15), exposed to varicella at home (OR 6.4, 95% CI: 2.6-16), or had a persistent high fever (OR 9.6, 95% CI: 2.8-33). Antipyretic regimen was associated with several measures of varicella illness severity among the controls. The risk of necrotizing soft tissue infection was not associated with the use of ibuprofen before the development of signs or symptoms of this complication (OR 1.3, 95% CI: 0.33-5.3). Risk of any invasive GAS infection was increased among children who had received ibuprofen (OR 3.9, 95% CI: 1.3-12), but not acetaminophen (OR 1.2, 95% CI: 0.50-3.0). However, there was no evidence of increasing risk with increasing duration of ibuprofen use. Subgroup analyses revealed that the risk of invasive GAS infection was increased only among children who had received both acetaminophen and ibuprofen. CONCLUSIONS: These data do not support the hypothesis that nonsteroidal antiinflammatory drugs, or ibuprofen in particular, increase the risk of necrotizing GAS infections. A statistically significant association was observed between nonnecrotizing invasive GAS infection and ibuprofen use; however, because of potential confounding, the meaning of this unexpected result is unclear. Nonetheless, these data suggest that parents use ibuprofen or ibuprofen together with acetaminophen to treat high fever and severe illness, which seems to identify children at high risk for invasive GAS infection.

Investigation by atomic force microscopy of forces at the origin of cement cohesion.

In cement paste, the cohesion results of the interactions between calcium silicate hydrate (CSH) surfaces in an interstitial ionic solution. (N, V, T) Monte Carlo simulations show that the interactions are due to the ion correlation forces influenced by the surface charge density, the ionic concentration and the ion valence. This paper deals with the direct measurement in solutions by atomic force microscopy (AFM) of the forces and the interaction ranges between a probe and an atomically smooth substrate covered by CSH nanoparticles. Different electrolytic solutions (Ca(OH)2, CaCl2, NaCl, NaOH) have been used in order to determine influent parameters permitting to identify the nature of acting forces. Investigations have been rendered possible by selecting appropriate experimental setup and solutions. The selected probe and substrate on which CSH nanoparticles have previously grown are neutral regarding the reactivity during experiments permitting the exchange of solutions. Results show that a force originates from electrostatic nature and differs from Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Agreement is found between experiments and (N,V,T) Monte Carlo simulations of ionic correlation forces. These forces are at the origin of the cohesion of cement paste.

Early onset baldness and prostate cancer risk.

Prostatic carcinoma is the leading cancer among American men, yet few risk factors have been established. Although increased androgen levels have long been associated with both prostatic carcinoma and baldness, to date no studies have shown an association between hair patterning and prostate cancer risk. A lack of standardized instruments to assess baldness or the assessment of hair patterning during uninformative periods of time may have precluded the ability of previous studies to detect an association. We hypothesized that baldness, specifically vertex baldness, should be assessed using standardized instruments and during early adulthood if an association with prostate cancer risk is to be found. To test this hypothesis, we included identical items related to hair patterning in surveys that were administered in two distinct prostate cancer case-control studies (Duke-based study, n = 149; 78 cases; 71 controls and community-based study, n = 130; 56 cases; 74 controls). In each, participants were provided with an illustration of the Hamilton Scale of Baldness and asked to select the diagrams that best represented their hair patterning at age 30 and again at age 40. From these data, the following five categories were created and compared: not bald (referent group); vertex bald early onset (by age 30); vertex bald later onset (by age 40); frontal bald early onset (by age 30); frontal bald later onset (by age 40); and frontal (at age 30) to vertex bald (at age 40). Separate analyses of the two studies are consistent and suggest an association between vertex baldness and prostate cancer [vertex bald early onset odds ratios, 2.44 [confidence interval (CI), 0.57-10.46)] and 2.11 (CI, 0.66-6.73), respectively; vertex bald later onset odds ratios, 2.10 (CI, 0.63-7.00) and 1.37 (CI, 0.47-4.06), respectively]. Although statistical significance was not achieved in either one of these studies, the concordance between the data suggests a need for future studies to determine whether early onset vertex baldness serves as a novel biomarker for prostate cancer and whether androgen production, metabolism, or receptor status differs among these men when compared to those who exhibit other types of hair patterning.

The safety of acetaminophen and ibuprofen among children younger than two years old.

BACKGROUND: Recently ibuprofen has been introduced as a nonprescription analgesic/antipyretic for use in children. OBJECTIVE: To compare the incidence of serious adverse clinical events among children <2 years old given ibuprofen and acetaminophen to control fever. STUDY DESIGN: A practitioner-based, randomized clinical trial. A total of 27 065 febrile children were randomized to receive acetaminophen (12 mg/kg), ibuprofen (5 mg/kg), or ibuprofen (10 mg/kg). Rates of hospitalization for acute gastrointestinal bleeding, acute renal failure, anaphylaxis, Reye's syndrome, asthma, bronchiolitis, and vomiting/gastritis were compared by randomization group. RESULTS: The risk of hospitalization with any diagnosis in the 4 weeks after enrollment was 1.4% (95% confidence interval, 1. 3%-1.6%) and did not vary by antipyretic assignment. No children were hospitalized for acute renal failure, anaphylaxis, or Reye's syndrome. Three children were hospitalized with gastrointestinal bleeding; all 3 had been assigned to treatment with ibuprofen. The risk of hospitalization with gastrointestinal bleeding among children randomized to ibuprofen was 17 per 100 000 (95% confidence interval, 3.5-49 per 100 000) but was not significantly greater than the risk among children given acetaminophen. The risk of hospitalization with asthma, bronchiolitis, or vomiting/gastritis did not differ by antipyretic assignment. CONCLUSIONS: The risk of serious adverse clinical events among children <2 years old receiving short-term treatment with either acetaminophen or ibuprofen suspension was small and did not vary by choice of medication. These data do not provide any information on the safety of these medications when used for prolonged periods or when used together, regardless of duration.

Vasectomy and prostate cancer.

PURPOSE: Vasectomy has been associated with an increased risk of prostate cancer in some previous studies but not in others. We evaluated the association in a population based, case control study in Massachusetts. MATERIALS AND METHODS: Included in our study were 1,216 patients younger than 70 years with newly diagnosed prostate cancer and 1,400 controls with no history of prostate cancer who were matched to patients by age and town of residence. Data on vasectomy and potential confounding factors were obtained by telephone interview, and confounding was controlled by conditional logistic regression analysis. RESULTS: Overall 16% of patients and 15% of controls had undergone vasectomy. Compared with no vasectomy the odds ratio for ever having undergone vasectomy was 1.0 (95% confidence interval [CI] 0.8 to 1.3), which did not vary significantly by age at or interval since vasectomy. In men who reported urological symptoms and those without symptoms the odds ratio was 0.9 (95% CI 0.7 to 1.2) and 1.4 (1.0 to 1.9), respectively. In men younger than 55 years and those 55 years old or older at diagnosis of prostate cancer the odds ratio was 1.9 (95% CI 1.2 to 3.2) and 1.0 (0.8 to 1.3), respectively [corrected]. In the younger men with stages A or B and C or D disease the odds ratio was 2.3 (95% CI 1.2 to 4.3) and 1.3 (0.5 to 3.5), respectively. CONCLUSIONS: Our findings do not support the hypothesis that vasectomy increases the risk of prostate cancer in men older than 55 years. Further study is needed to determine whether the observed association between vasectomy and prostate cancer in men younger than 55 years is due to chance, detection bias or a causal effect.

Effect of metoclopramide dose on preventing emesis after oral administration of N-acetylcysteine for acetaminophen overdose.

OBJECTIVE: To determine the effect of the metoclopramide dose on the prevention of vomiting of N-acetylcysteine in acetaminophen overdose. METHODS: Patients with acetaminophen ingestions receiving metoclopramide prior to emergency department administration of N-acetylcysteine were included. Emergency Department and poison center records were reviewed for administration of metoclopramide pre-N-acetylcysteine and incidence of subsequent vomiting. The treatment group was defined as patients receiving high-dose metoclopramide (20-50 mg intravenously) prior to the loading dose of N-acetylcysteine. Controls were patients receiving standard-dose (< 20 mg intravenously) metoclopramide prior to loading dose of N-acetylcysteine. Outcome was vomiting within 60 minutes of N-acetylcysteine administration. RESULTS: Twelve of 19 patients (63%) receiving standard-dose metoclopramide vomited N-acetylcysteine. Only 5 of 23 patients (22%) receiving high-dose metoclopramide vomited N-acetylcysteine (crude odds ratio: 6.2; 95% CI [1.3-30.3]). After controlling for confounding in the logistic regression model, the effect of high-dose metoclopramide in preventing vomiting of N-acetylcysteine remained significant (adjusted odds ratio: 17.0; 95% CI [2.6-110.0]). CONCLUSION: This study supports the efficacy of high-dose metoclopramide to prevent emesis after the oral loading dose of N-acetylcysteine.

Changes in sleep position during infancy: a prospective longitudinal assessment.

CONTEXT: Prone sleeping by infants has been associated with an increased risk of sudden infant death syndrome. OBJECTIVE: To document the prevalence of and identify risk factors for prone sleeping during the first 6 months of life. DESIGN: Prospective cohort study. SETTING: Eastern Massachusetts and northwest Ohio. STUDY PARTICIPANTS: A total of 7796 mothers of infants weighing 2500 g or more at birth. MAIN OUTCOME MEASURES: Maternal and infant characteristics related to prone sleeping at 1 month and 3 months of age. RESULTS: Between 1 month and 3 months of age, prone sleeping increased from 18% to 29%. At 1 month, prone sleeping was associated with the following maternal characteristics: non-Hispanic black or Hispanic race/ethnicity, younger age, less education, and higher parity. At 3 months, switching from nonprone to prone position was associated with mother's race/ethnicity of non-Hispanic black (odds ratio [OR], 1.7; 95% confidence interval [CI], 1.2-2.3) or Hispanic (OR, 1.5; 95% CI, 1.1-2.2); younger maternal age (compared with mothers >34 years: 18-24 years, OR, 1.6; 95% CI, 1.2-2.2; <18 years, OR, 2.2; 95% CI, 1.2-4.3); increasing parity (compared with 1 child: 2 children, OR, 1.5; 95% CI, 1.2-1.8; > or =3 children, OR, 1.7; 95% CI, 1.4-2.2); and infant sex (male sex, OR, 1.4; 95% CI, 1.2-1.7). CONCLUSIONS: If infant sleeping practices in the study communities are representative of practices throughout the United States, a substantial number of infants who slept nonprone at 1 month sleep prone at 3 months.

Calcium channel blocker use and the risk of prostate cancer.

A recent study suggested that the risk of all cancers, including prostate cancer, is increased by the use of calcium channel blockers. The objective of this study was to determine whether prostate cancer is associated with calcium channel blocker use. A case-control study was conducted in Massachusetts using cases diagnosed from December 1992 through February 1995. Cases were men identified by tumor registrars who were less than 70 years old with newly diagnosed prostate cancer. Controls were men with no history of prostate cancer or symptoms of undiagnosed prostate cancer, and were matched to the cases on precinct of residence and half-decade of age. A total of 1217 cases of prostate cancer and 1400 community controls are included in this analysis. Data were collected by telephone interview. Multiple logistic regression was used to estimate relative risks for calcium channel blockers use while controlling for confounding. The relative risk for prostate cancer for any use of calcium channel blockers relative to nonuse was 1.2 (95% confidence interval [CI], 0.9-1.5). There was no evidence of a trend according to duration of use. When the analysis was confined to symptomatic men, the relative risk estimate was 1.1 (0.8-1.4) overall and 1.2 (0.8-1.7) among those aged 65 to 69 years. Relative risk estimates for the use of other classes of antihypertensive drugs among symptomatic men were close to 1.0; the corresponding estimates among asymptomatic men were generally further from 1.0. These findings suggest that calcium channel blockers do not increase the risk of prostate cancer. The differences in the relative risk estimates between symptomatic and asymptomatic men are compatible with detection bias. Because of the widespread use of Prostate-Specific Antigen testing for early detection of prostate cancer, potential detection bias needs to be considered in future studies of prostate cancer.

Serum androgens: associations with prostate cancer risk and hair patterning.

Cancer of the prostate is the leading cancer among American men, yet few risk factors have been established. Hair growth and development are influenced by androgens, and it has long been suspected that prostate cancer also is responsive to these hormones. A blinded, case-control study was undertaken to determine if hair patterning is associated with risk of prostate cancer, as well as specific hormonal profiles. The study accrued 315 male subjects who were stratified with regard to age, race, and case-control status (159 prostate cancer cases/156 controls). Hair-patterning classification and serum levels of total and free testosterone (T), sex hormone binding globulin, and dihydrotestosterone (DHT) were performed. Data indicate that hair patterning did not differ between prostate cancer cases and controls; however, significant hormonal differences were detected between the two groups. Free T was greater among cases than in controls (16.4 +/- 6.1 vs. 14.9 +/- 4.8 pg/ml, P = 0.02). Conversely, DHT-related ratios were greater among controls (P = 0.03 for DHT/T and P = 0.01 for DHT/free T). Several strong associations also were found between hormone levels and hair patterning. Men with vertex and frontal baldness had higher levels of free T (16.5 +/- 5.5 and 16.2 +/- 8.0 pg/ml, respectively) when compared to men with either little or no hair loss (14.8 +/- 4.7 pg/ml) (P = 0.01). Data suggest that increased levels of free T may be a risk factor for prostatic carcinoma. In addition, although no differences in hair patterning were detected between cases and controls within this older population, further research (i.e., prospective trials or case-control studies among younger men) may be necessary to determine if hair patterning serves as a viable biomarker for this disease, especially given the strong association between free T levels and baldness.

Renal function after short-term ibuprofen use in infants and children.

OBJECTIVE: To test the hypothesis that short-term use of ibuprofen increases the risk of impaired renal function in children. STUDY DESIGN: Randomized, double-blind acetaminophen-controlled clinical trial. Children with a febrile illness were enrolled from outpatient pediatric and family medicine practices and randomly assigned to receive either acetaminophen suspension or one of two dosages of ibuprofen suspension (5 mg/kg or 10 mg/kg) for fever control. RESULTS: Mean blood urea nitrogen levels on admission among children admitted to hospital and assigned ibuprofen 5 mg/kg (n = 96), ibuprofen 10 mg/kg (n = 102), and acetaminophen 12 mg/kg (n = 87) were 4.1, 3.8, and 3.9 mmol/L, respectively. The corresponding creatinine levels were 43, 41, and 43 micromol/L, respectively. The prevalence of a creatinine level >62 micromol/L was 9.5% overall and did not vary by antipyretic assignment. Among 83 children hospitalized with dehydration, the mean creatinine level was 44 micromol/L, and the prevalence of an elevated creatinine was 14%; neither measure varied by antipyretic assignment. CONCLUSION: Although renal failure in children has been reported after ibuprofen use, these data suggest that for short-term use the risk of less severe renal impairment, as reflected by blood urea nitrogen and creatinine levels, is small and not significantly greater than that after acetaminophen use.

Detection of intact prostate cancer cells in the blood of men with prostate cancer.

OBJECTIVES: To develop a procedure to be used to find, identify, and characterize the living prostate cancer cells in the blood of patients with prostate cancer. METHODS: The procedure is based on a negative selection approach that removes most of the blood cells and collects the remaining prostate cancer cells, which are identified and characterized by fluorescent in situ hybridization with deoxyribonucleic acid probes and by indirect fluorescent immunocytochemical staining. The blood cells are removed via density gradient centrifugation. RESULTS: Using the prostate cancer LNCaP cells as a model, the recovery rate of the added prostate cancer cells to 10 mL of blood was about 85%, with a dilution of 1 LNCaP cell to 10,000 white blood cells or more. Blood samples varying from 9 to 27 mL were collected and analyzed from 8 men aged 54 to 79 years who had varying levels of PSA in serum. In one blood sample, prostate cancer cells were not found; in the seven other samples, the number of prostate cancer cells found per milliliter of blood varied from 1 to 20. Prostate cancer cells were not found in 7.5 to 15-mL blood samples from 3 healthy younger men. The prostate cells were found to be aneuploid for chromosomes 7 and 8, highly suggestive that these cells were cancerous. CONCLUSIONS: Using a negative selection approach, prostate cells can be found in the blood of patients with prostate cancer, as identified by prostate cell-specific probes and antibodies. These cells were found to be aneuploid.

Formation, intracellular distribution and efflux of glutathione-bimane conjugates in drug-sensitive and -resistant MCF-7 cells.

The rate of reaction of monochlorobimane with glutathione (GSH) was measured in native human mammary MCF-7 adenocarcinoma cells (MCF-7wt) and sublines displaying resistance to 4-hydroperoxycyclophosphamide (MCF-7hc) and adriamycin (MCF-7adr) prior to examination by epifluorescence and confocal microscopy. After a 60-min incubation period at 37 degrees C, essentially all GSH was conjugated in the MCF-7wt and MCF-7adr cell lines whereas only 80% of the GSH was conjugated in the MCF-7hc line. All three lines displayed significant export of the conjugate from the cell during this period, with the MCF-7adr line displaying the most rapid efflux with 85% of the conjugate exported within 60 min. Epifluorescence microscopy detected an approximately 20% increase in integrated fluorescence intensity in the nuclear region in all three lines. Confocal microscopy however, indicated that most of the cells examined showed a homogeneous fluorescence distribution. The cells grown in monolayers were found to be thicker in the nuclear region suggesting that the observed increase in fluorescence intensity in the nuclear region in the images from epifluorescence microscopy was probably derived from fluorescence from an out-of-focus plane. Cells depleted of GSH with buthionine sulfoximine followed by treatment with mBCl showed significant fluorescence intensity resulting from nonspecific binding of this probe. These studies illustrate the need for measuring the rate of GSH conjugate export and for determining probe specificity, and emphasizes the need for using confocal techniques for the quantitative evaluation of the distribution of intracellular fluorescence.

Family history and prostate cancer risk.

The authors examined the relation between family history of prostate cancer and the risk of this cancer in a population-based case-control study conducted in Massachusetts between December 1992 and October 1994. Cases were all incident cases of prostate cancer in men younger than 70 years (n = 563); controls were men with no history of the disease matched to the cases on age and town of residence (n = 703). Prostate cancer risk was increased among men who reported a history of this cancer in either their fathers or brothers (odds ratio (OR) = 2.3, 95% confidence interval (CI) 1.7-3.3). Risk varied with the number of relatives affected and their relationship to the case. For a history of prostate cancer in one relative, the OR was 2.2 (95% CI 1.5-3.2); if two or more relatives were affected, it was 3.9 (95% CI 1.7-5.2). For prostate cancer in the father, the OR was 1.9 (95% CI 1.2-3.0); for prostate cancer in a brother, it was 3.0 (95% CI 1.8-4.9). Risk was inversely related to the subject's age and to age at diagnosis of prostate cancer in his affected relative. Among probands younger than 60 years, the OR was 5.3 (95% CI 2.5-12); for those 60-64 years of age, the OR was 2.7 (95% CI 1.3-5.5); and for those 65 years of age and older, the OR was 1.6 (95% CI 1.0-2.5). For prostate cancer diagnosed in a relative before age 65, the OR was 4.1 (95% CI 2.3-7.3); for detection of the disease after age 74, the OR was 0.76 (95% CI 0.38-1.5). The association was present both among men with local and advanced stage disease and among men whose prostate cancer was detected either by screening or because of symptoms. These data provide evidence that after controlling for diet and other potential confounders, familial factors are significantly associated with the risk of prostate cancer.

The experimental homologous and heterologous separation distance histograms for the centromeres of chromosomes 7, 11, and 17 in interphase human T-lymphocytes.

The simultaneous 3D arrangement of the interphase centromeres of chromosomes 7, 11, and 17 in unstimulated human T-lymphocytes is analyzed. Using triple in situ hybridization in combination with optical sectioning and image processing, the identification of three pairs of centromeres in each nucleus and the assignment of 3D coordinates to each centromere are made. The homologous and heterologous centromere separation distance histograms are determined and compared to the hypothesized histograms for randomly distributed centromeres. The experimental nuclei are truncated spheres in shape with a principal radius of 3.7 +/- 0.3 micron and a truncated hemispherical height of 2.6 micron. None of the separation distance distributions appears to be statistically significantly different from a random model distribution.

When a randomised controlled trial is needed to assess drug safety. The case of paediatric ibuprofen.

Drugs are frequently made available for use before risks of rare but serious reactions have been identified and quantified. While this situation may be acceptable for drugs used to treat serious conditions, greater information on safety is needed for drugs used to treat less serious conditions, and particularly those medications available without prescription. Spontaneous reports and observational studies can provide useful data in most instances, but nonrandomised studies are inadequate in the presence of confounding by indication (i.e. when patients treated with a drug differ in their underlying risk of adverse outcome from patients given alternate treatments, independent of the effect of the drug). Such is the case in the US with regard to the use of paediatric ibuprofen as an antipyretic. In this setting, a rigorous and large randomised controlled trial is needed to provide valid and statistically stable risk estimates. A trial of this kind is a feasible way to develop clinically meaningful data on safety with respect to rare but serious adverse reactions.

An assessment of the safety of pediatric ibuprofen. A practitioner-based randomized clinical trial.

OBJECTIVE: To test the hypothesis that ibuprofen increases the risk of hospitalization for gastrointestinal bleeding, renal failure, or anaphylaxis among febrile children. DESIGN: Randomized double-blind acetaminophen-controlled trial. SETTING: Outpatient pediatric and family medicine practices. PATIENTS: A total of 84,192 children. INTERVENTION: Patients were randomly assigned to receive 12 mg/kg of acetaminophen, 5 mg/kg of ibuprofen, or 10 mg/kg of ibuprofen. MAIN OUTCOME MEASURES: Hospitalizations for acute gastrointestinal bleeding, acute renal failure, and anaphylaxis. RESULTS: A total of 277 patients (0.3%) were unavailable for follow-up. Overall, 795 participants (1%) were hospitalized, primarily for infectious diseases; hospitalization rates did not differ according to treatment group. Four children had diagnoses of acute, nonmajor gastrointestinal bleeding (two in each ibuprofen dosage group); among ibuprofen-treated children, the observed risk of gastrointestinal bleeding, 7.2 per 100,000 (95% confidence interval, 2 to 18 per 100,000), was not significantly different from the risk among acetaminophen-treated children (P = .31). There were no hospitalizations for acute renal failure or anaphylaxis; the upper 95% confidence bound for the risk of either of these outcomes was 5.4 per 100,000 ibuprofen-treated children. Among a number of other possibly serious adverse drug events, low white blood cell count was marginally associated with ibuprofen treatment. Because this association was observed in the setting of multiple comparisons and white blood cell counts may have been low before treatment, causation is unclear. CONCLUSIONS: The risk of hospitalization for gastrointestinal bleeding, renal failure, or anaphylaxis was not increased following short-term use of ibuprofen in children. These data, however, provide no information on the risks of less severe outcomes or the risks of prolonged ibuprofen use.