Commonly used antibacterial and antifungal agents for hospitalised paediatric patients: implications for therapy with an emphasis on clinical pharmacokinetics

Antibiotic perturbations to the gut microbiome

Antibiotic-mediated perturbation of the gut microbiome is associated with numerous infectious and autoimmune diseases of the gastrointestinal tract. Yet, as the gut microbiome is a complex ecological network of microorganisms, the effects of antibiotics can be highly variable. With the advent of multi-omic approaches for systems-level profiling of microbial communities, we are beginning to identify microbiome-intrinsic and microbiome-extrinsic factors that affect microbiome dynamics during antibiotic exposure and subsequent recovery. In this Review, we discuss factors that influence restructuring of the gut microbiome on antibiotic exposure. We present an overview of the currently complex picture of treatment-induced changes to the microbial community and highlight essential considerations for future investigations of antibiotic-specific outcomes. Finally, we provide a synopsis of available strategies to minimize antibiotic-induced damage or to restore the pretreatment architectures of the gut microbial community.

Renal replacement therapy in the management of intoxications in children: recommendations from the Pediatric Continuous Renal Replacement Therapy (PCRRT) workgroup

BACKGROUND

Intentional or unintentional ingestions among children and adolescents are common. There are a number of ingestions amenable to renal replacement therapy (RRT).

METHODS

We systematically searched PubMed/Medline, Embase, and Cochrane databases for literature regarding drugs/intoxicants and treatment with RRT in pediatric populations. Two experts from the PCRRT (Pediatric Continuous Renal Replacement Therapy) workgroup assessed titles, abstracts, and full-text articles for extraction of data. The data from the literature search was shared with the PCRRT workgroup and two expert toxicologists, and expert panel recommendations were developed.

RESULTS AND CONCLUSIONS

We have presented the recommendations concerning the use of RRTs for treatment of intoxications with toxic alcohols, lithium, vancomycin, theophylline, barbiturates, metformin, carbamazepine, methotrexate, phenytoin, acetaminophen, salicylates, valproic acid, and aminoglycosides.

Azithromycin Extravasation in a Pediatric Patient

Objective:

To report a case of azithromycin infiltration and extravasation in a pediatric patient.

Case Summary:

A 12-month-old African American male, between chemotherapy cycles for acute myelogenous leukemia, self-dislodged his central venous catheter. A peripheral catheter was placed in the right dorsal hand and, 2 days later, azithromycin for injection infiltrated at the infusion site. Several bullae formed in the first web space and a few areas of epidermolysis, each <2 cm wide, later appeared on the forearm. Treatment included warm compresses, adaptee dressing, topical antibiotics, splint placement, and arm elevation. Four months after the incident, there was no visible impairment or restriction to the toddler's use of the right hand or arm. The only residual finding was an area of hypopigmented skin in the dorsal web between the first and second fingers.

Discussion:

As of February 10, 2005, this is the first case published in the English-language literature describing intravenous azithromycin infiltration and extravasation. Infiltration occurs generally by 3 mechanisms. These include the catheter dislodging or causing a hole in the vessel wall, intravenous fluid irritating the vessel wall leading it to rupture or leak, or backflow of intravenous fluid through the catheter insertion site.

Conclusions:

Complications can occur secondary to intravascular therapy, including extravascular extravasation. In this case, infiltration and extravasation injury were probably related to azithromycin. Immediate detection and treatment are critical to decrease morbidity associated with infiltration events.

Pharmacokinetics of antibacterial agents in the CSF of children and adolescents

The adequate management of central nervous system (CNS) infections requires that antimicrobial agents penetrate the blood-brain barrier (BBB) and achieve concentrations in the CNS adequate for eradication of the infecting pathogen. This review details the currently available literature on the pharmacokinetics (PK) of antibacterials in the CNS of children. Clinical trials affirm that the physicochemical properties of a drug remain one of the most important factors dictating penetration of antimicrobial agents into the CNS, irrespective of the population being treated (i.e. small, lipophilic drugs with low protein binding exhibit the best translocation across the BBB). These same physicochemical characteristics determine the primary disposition pathways of the drug, and by extension the magnitude and duration of circulating drug concentrations in the plasma, a second major driving force behind achievable CNS drug concentrations. Notably, these disposition pathways can be expected to change during the normal process of growth and development. Finally, CNS drug penetration is influenced by the nature and extent of the infection (i.e. the presence of meningeal inflammation). Aminoglycosides have poor CNS penetration when administered intravenously. Intrathecal gentamicin has been studied in children with more promising results, often exceeding the minimum inhibitory concentration. There are very limited data with intrathecal tobramycin in children. However, in the few patients that have been studied, the CSF concentrations were highly variable. Penicillins generally have good CNS penetration. Aqueous penicillin G reaches greater concentrations than procaine or benzathine penicillin. Concentrations remain detectable for ≥ 12 h. Of the aminopenicillins, both ampicillin and parenteral amoxicillin reach adequate CNS concentrations; however, orally administered amoxicillin resulted in much lower concentrations. Nafcillin and piperacillin are the final two penicillins with pediatric data: their penetration is erratic at best. Cephalosporins vary greatly in regard to their CSF penetration. Few first- and second-generation cephalosporins are able to reach higher CSF concentrations. Cefuroxime is the only exception and is usually avoided due to its adverse effects and slower sterilization of the CSF than third-generation agents. Ceftriaxone, cefotaxime, ceftazidime, cefixime and cefepime have been studied in children and are all able to adequately penetrate the CSF. As with penicillins, concentrations are greatest in the presence of meningeal inflammation. Meropenem and imipenem are the only carbapenems with pediatric data. Imipenem reaches higher CSF concentrations; however, meropenem is preferred due to its lower incidence of seizures. Aztreonam has also demonstrated favorable penetration but only one study has been completed in children. Both chloramphenicol and sulfamethoxazole/trimethoprim (cotrimoxazole) penetrate into the CNS well; however, significant toxicities limit their use. The small size and minimal protein binding of fosfomycin contribute to its favorable CNS PK. Although rarely used, it achieves higher concentrations in the presence of inflammation and accumulation is possible. Linezolid reaches high CSF concentrations; however, more frequent dosing might be required in infants due to their increased elimination. Metronidazole also has very limited information but it demonstrated favorable results similar to adult data; CSF concentrations even exceeded plasma concentrations at certain time points. Rifampin (rifampicin) demonstrated good CNS penetration after oral administration. Vancomycin demonstrates poor CNS penetration after intravenous administration. When combined with intraventricular therapy, CNS concentrations are much greater. Of the antituberculosis agents, isoniazid, pyrazinamide and streptomycin have been studied in children. Isoniazid and pyrazinamide have favorable CSF penetration. Streptomycin appears to produce unpredictable CSF levels. No pediatric-specific data are available for clindamycin, daptomycin, macrolides, tetracyclines, and fluoroquinolones. Daptomycin, fluoroquinolones, and tetracyclines have demonstrated favorable CNS penetration in adults; however, data are limited due to their potential pediatric-specific toxicities and newness within the marketplace. Macrolides and clindamycin have demonstrated poor CNS penetration in adults and thus have not been studied in pediatrics.

Intraocular penetration of itraconazole in patient with fungal endophthalmitis

The purpose of this study was to determine the penetration of itraconazole, a type of azole antifungal agent, into the aqueous humor and vitreous after repeated oral administrations. Fungal endophthalmitis developed bilaterally in a 21-year-old man who had a history of intravenous hyperalimentation following abdominal surgery. Itraconazole capsules (200 mg/day) were taken orally for 12 consecutive days. Vitrectomy was performed on the left eye 30 h after the last oral itraconazole. Samples of blood, aqueous, and vitreous were collected during the vitrectomy. The concentration of itraconazole was determined by high performance liquid chromatography. The concentration of itraconazole was 0.492 μg/mL in the plasma, 0.020 μg/mL in the vitreous, and none in the aqueous of the left eye. Although no fungal organisms were isolated from the plasma and vitreous samples from both eyes, fungal DNA was detected in the vitreous from the left eye. Our findings indicate that oral itraconazole has limited penetration in eyes with fungal endophthalmitis.

Pharmacokinetics and tolerability of single-dose daptomycin in young infants

BACKGROUND

Daptomycin is approved for the treatment of complicated skin and skin-structure infections and Staphylococcus aureus bacteremia. We sought to characterize daptomycin single-dose pharmacokinetics and tolerability in young infants.

METHODS

Subjects < 120 days of age with suspected systemic infections were eligible for inclusion. Each subject was given a single 6 mg/kg intravenous dose of daptomycin. An average of 4 postdose concentrations per infant was obtained.

RESULTS

Data from 20 infants are presented. Median gestational age at birth and postnatal age were 32 weeks (range: 23, 40) and 3 days (1, 85), respectively. The median area under the concentration curve at 24 hours, volume of distribution, total body clearance and half-life of daptomycin were 262.4 mg×h/L (166.7, 340.2), 0.21 L/kg (0.11, 0.34), 0.021 L/h/kg (0.016, 0.034) and 6.2 hours (3.7, 9.0), respectively. No adverse events related to daptomycin were observed, including changes in creatine phosphokinase concentrations.

CONCLUSIONS

Daptomycin clearance in young infants was similar to that in children 2-6 years of age and higher than that observed in adolescents and adults.

Endogenous Candida endophthalmitis

Intraocular Candida infections, although uncommon, represent an important clinical problem owing to the potential for visual loss, which can be bilateral. Candida chorioretinitis and endophthalmitis are complications of systemic candidiasis with extension of the fungal pathogens to the uvea and retina. Early diagnosis and prompt management significantly affect the visual prognosis for these patients. This review evaluates the current literature on Candida endophthalmitis and includes discussion on presentation, diagnosis and management strategies. New systemic and intravitreal antifungal agents are also reviewed in the context of the management of intraocular fungal infection.

Neonatal chlamydial infections: prevention and treatment

Neonatal chlamydial infection, which manifests principally as ophthalmia neonatorum (ON) or pneumonia, is a significant cause of neonatal morbidity. Widespread use of silver nitrate drops resulted in a dramatic decline in the incidence of gonococcal ophthalmia but had much less impact on the incidence of neonatal chlamydial infection. Chlamydia trachomatis has become the most common infectious cause of ON in developed countries.A number of prophylactic antibiotic or antiseptic agents have been used to prevent ON. Prophylaxis with 1% silver nitrate ophthalmic drops, 0.5% erythromycin ophthalmic ointment, or 1% tetracycline ointment has comparable efficacy for the prevention of chlamydial ophthalmia but does not offer protection against nasopharyngeal colonization or the development of pneumonia. Erythromycin or tetracycline topically have been used as prophylactic agents because of their allegedly superior activity for the prevention of ON and because they produced less chemical conjunctivitis compared with silver nitrate. However, the relative efficacy of these agents for chlamydial infection and the emergence of beta-lactamase-producing Neisseria gonorrheae has raised questions regarding their effectiveness when applied topically for prophylaxis of ON. Compared with these agents, a 2.5% povidone-iodine ophthalmic solution has been found to have greater efficacy for the prevention of ON generally, and chlamydial ophthalmia specifically. In countries where the incidence of ON is very low, an alternative strategy is to institute prenatal screening and treatment of infected mothers, forgo routine neonatal prophylaxis, and follow-up infants after birth for the possible development of infection. For the treatment of chlamydial ophthalmia or pneumonia, oral erythromycin for 2 weeks is recommended; additional topical therapy is unnecessary. However, in approximately 20-30% of infants, therapy will not eradicate the organism and the infant may require a repeat oral course of antibiotics. The few published studies on the use of the new oral macrolide antibiotics, such as azithromycin, roxithromycin, or clarithromycin for chlamydial infections in neonates suggest that these agents may be effective; however, more data on their tolerability and efficacy in this patient group are warranted.

Population pharmacokinetics of ciprofloxacin in pediatric and adolescent patients with acute infections

The aim of the present study was to characterize the population pharmacokinetics of ciprofloxacin in patients with and without cystic fibrosis ranging in age from 1 day to 24 years and to propose a limited sampling strategy to estimate individual pharmacokinetic parameters. Patients were divided into four groups according to the treatment schedule. They received ciprofloxacin by intravenous infusion (30 min) or by the oral route. The number of samples collected from each patient ranged from 1 to 12. The population parameters were computed for an initial group of 37 patients. The data were analyzed by nonlinear mixed-effect modeling by use of a two-compartment structural model. The interindividual variability in clearance (CL) was partially explained by a dependence on age and the patient's clinical status. In addition, a significant relationship was found between weight and the initial volume of distribution. Eighteen additional patients were used for model validation and evaluation of limited sampling strategies. When ciprofloxacin was administered intravenously, sampling at a single point (12 h after the start of infusion) allowed the precise and accurate estimation of CL and the elimination half-life, as well as the ciprofloxacin concentration at the end of the infusion. It should be noted that to take into account the presence of a lag time after oral administration, a schedule based on two sampling times of 1 and 12 h is needed. The results of this study combine relationships between ciprofloxacin pharmacokinetic parameters and patient covariates that may be useful for dose adjustment and a convenient sampling procedure that can be used for further studies.

Linezolid pharmacokinetics in pediatric patients: an overview

BACKGROUND

There are a number of physiologic and developmental differences between children and adults that can influence the absorption, distribution, metabolism and elimination of a drug. Therefore it is important to determine the specific pharmacokinetic characteristics for individual drugs in pediatric patients so that appropriate age-specific dosage regimens can be developed and evaluated in clinical trials. This review summarizes the pharmacokinetic parameters of linezolid in pediatric patients and the rationale for the approved dosing recommendations for this population.

METHODS

The pharmacokinetics of linezolid in pediatric patients has been evaluated in 4 clinical trials, including >180 patients ranging in age from preterm newborn infants up to 18 years of age. In all of these studies, patients received a single intravenous dose of linezolid. Plasma linezolid concentrations have been determined by validated high performance liquid chromatography (adult studies) or liquid chromatography/mass spectrometry/mass spectrometry (pediatric studies) methods.

RESULTS

The pharmacokinetics of linezolid, especially elimination clearance, is age-dependent. Children younger than 12 years of age have a smaller area under the drug concentration-time curve, a faster clearance and a shorter elimination half-life than adults. Although clearance rates in newborn infants are similar to those in adults, clearance increases rapidly during the first week of life, becoming 2- to 3-fold higher than in adults by the seventh day of life. The clearance of linezolid decreases gradually among young children, becoming similar to adult values by adolescence. The pharmacokinetics of linezolid in children age 12 years and older is not significantly different from that of adults.

CONCLUSIONS

Because of the higher clearance and lower area under the drug concentration-time curve, a shorter dosing interval for linezolid is required for children younger than 12 years of age to produce adequate drug exposure against target Gram-positive pathogens.