Flow Rate Deviation in Infusion Pump: Infusion Set Defect Enables Pump Malfunction and Considerable Accuracy Deviation.

Volumetric infusion pumps are used together with infusion sets to deliver medication to patients. Flow rate errors leading to overinfusion or underinfusion are known problems with these devices. Recently, numerous underinfusion flow rate errors were reported at a Swedish hospital. This experimental study reports on the investigation of these errors and specifically investigates the effect of operating the pump with a defective infusion set that has a visible elongation of the silicone segment of the set. Pump flow rate accuracy testing was performed using a gravimetric method. Experiments included a manipulated infusion set and a defective infusion set used in clinic. The use of a defective infusion set resulted in considerable accuracy deviations. The pump reported an infused amount greater than what was infused and did not provide any alarm or information indicating a reduced output. Using an elongated infusion set, the pump can be brought into an erroneous operating state where the infused amount delivered by the pump is considerably less than what has been programmed and what is shown on the pump display. This could put the patient at risk of not receiving the intended medication within the appropriate time.

Frequency of paediatric patients administered extemporaneous preparations at a Swedish university hospital: a registry-based study comparing two study-years, 10 years apart.

BACKGROUND: Lack of child-friendly dosage forms and strengths often leads to manipulation of medicines at hospital units or by caregivers in the home setting. One alternative to manipulating dosage forms is the use of extemporaneous preparations. In Sweden, these are produced according to good manufacturing practice by a few extemporaneous pharmacies. OBJECTIVES: To compare frequencies of patients administered extemporaneous preparations in two separate years, 10 years apart. METHODS: This registry-based study describes and compares the frequency of extemporaneous oral preparations administered to paediatric patients in 2009 and 2019 at a Swedish university hospital.The study included 117 023 oral administrations (to 4905 patients) and 128 638 oral administrations (to 4718 patients) from 2009 and 2019, respectively. RESULTS: The frequency of inpatients administered one or more extemporaneous preparations increased from 22% in 2009 to 40% in 2019 (p<0.0001). The increase was observed in all age groups. The use of some active pharmaceutical ingredients increased (eg, captopril, clonidine, hydrocortisone, melatonin and propranolol), and some active pharmaceutical ingredients decreased between the study years (eg, midazolam and sildenafil). CONCLUSIONS: The introduction of new authorised products has decreased the need for manipulation or extemporaneous preparations in some therapeutic groups. There remains, however, a pronounced lack of commercially available child-friendly dosage forms and suitable strengths enabling safe administration of medicines to children, indicated by the large percentage of patients receiving at least one extemporaneous preparation.

Identifying neonatal adverse events in preterm and term infants using a paediatric trigger tool.

AIM: To explore the incidence and characteristics of inpatient neonatal adverse events in a Swedish setting. METHODS: A retrospective record review, using a trigger tool, performed by registered nurses and a neonatologist, at a University Hospital. The identified adverse events were categorised by, for example, preventability, severity and time of occurrence. RESULTS: A random selection of 150 admissions representing 3531 patient days were reviewed (mean [SD] birthweight 2620 [1120]g). Three hundred and sixty adverse events were identified in 78 (52.0%) infants, and 305 (84.7%) of these were assessed as being preventable. The overall adverse event rate was 240 per 100 admissions and 102.0 per 1000 patient days. Preterm infants had a higher rate than term infants (353 versus 79 per 100 admissions, p = 0.001); however, with regard to the length of stay, the rates were similar. Most adverse events were temporary and less severe (n = 338/360, 93.9%) and the most common type involved harm to skin, tissue or blood vessels (n = 163/360, 45.3%). Forty percent (n = 145) of adverse events occurred within the first week of admission. CONCLUSION: Adverse events were common in neonatal care, and many occurred during the first days of treatment. Characterisation of adverse events may provide focus areas for improvements in patient safety.

Manipulated Oral and Rectal Drugs in a Paediatric Swedish University Hospital, a Registry-Based Study Comparing Two Study-Years, Ten Years Apart.

This is a registry-based study with the aim of describing and comparing the frequency of manipulations of solid oral and rectal medicines in 2009 and 2019 at inpatient units and an emergency department in a paediatric hospital within a Swedish university hospital. All patients aged 1 month−18 years with oral or rectal administrations were included. In total, 140,791 oral and rectal administrations were included in 2009, and 167,945 oral and rectal administrations were included in 2019. The frequency of patients receiving at least one manipulated oral medicine decreased between the study years, both in inpatient units and in the emergency department (from 19% to 17%, p = 0.0029 and from 11% to 5%, p < 0.0001, respectively). The frequency of patients receiving a manipulated rectal medicine also decreased between the study years, both in inpatient units and in the emergency department (from 22% to 10%, p < 0.0001 and from 35% to 7% 2019, p < 0.0001, respectively). The results show a decrease in the manipulation of both oral and rectal medicines to paediatric patients in 2019 compared to 2009. Even though this implies a safer practice, there is still a pronounced lack of child-friendly dosage forms and suitable strengths enabling the safe administration of medicines to sick children.

Estimation of body surface area in neonates, infants, and children using body weight alone.

BACKGROUND: The aim of this study was to use Body Surface Area (BSA) data calculated with the Mosteller equation to test potential new equations that estimate BSA using Body Weight (BW) alone in children aged 0-18 years.Mosteller's equation, the golden standard at our hospital, was used to calculate the BSA in infants and children aged 0-18 years using BW and height data from 27,440 hospital visits by 20,635 patients over one year. METHODS: The best fit of three nonlinear regression equations (third-order polynomial, Meeh-type, and modified Boyd self-adjusting-type) to a plot of the calculated Mosteller BSA values versus BW was then investigated. The correlation between the BSA values estimated by these equations and the Mosteller BSA values was established by the Spearman rank correlation test. Bias and precision were evaluated as outlined by Sheiner and Beal. Measured and estimated BSA values were compared using the Eksborg plot. RESULTS: The estimated BSA values from all three equations and the BSA values from the Mosteller equation were closely correlated (P < .0001). The third-order polynomial and Meeh-type equations overestimated BSA by 0.13% and 0.40%, respectively, while the Boyd self-adjusted-type equation underestimated BSA by 0.060%. For the entire pediatric population, the best fit was obtained with the Meeh-type equation: 99.2% of the Meeh/Mosteller BSA ratios were within the range of 0.9-1.1 when compared with 98.3% and 97.2% for the polynomial and Boyd-type equations, respectively. CONCLUSION: A single Meeh-type equation can be used to predict the results of Mosteller equation when H is not available with high precision and accuracy in children aged 0-18 years, including term neonates. We now plan to include the results of this study in CPOE systems in Sweden to improve drug dosage in all children.

Association of Adherence to Surfactant Best Practice Uses With Clinical Outcomes Among Neonates in Sweden.

Importance: While surfactant therapy for respiratory distress syndrome (RDS) in preterm infants has been evaluated in clinical trials, less is known about how surfactant is used outside such a framework. Objective: To evaluate registered use, off-label use, and omissions of surfactant treatment by gestational age (GA) and associations with outcomes, mainly among very preterm infants (GA <32 weeks). Design, Setting, and Participants: This population-based cohort study used registry data for 97 377 infants born in Sweden between 2009 and 2018. Infants did not have malformations and were admitted for neonatal care. Data analysis was conducted from June 2019 to June 2020. Exposures: Timing and number of surfactant administrations, off-label use, and omission of use. Registered use was defined by drug label (1-3 administrations for RDS). Omissions were defined as surfactant not administered despite mechanical ventilation for RDS. Main Outcome and Measures: In-hospital survival, pneumothorax, intraventricular hemorrhage grade 3 to 4, duration of mechanical ventilation, use of postnatal systemic corticosteroids for lung disease, treatment with supplemental oxygen at 28 days' postnatal age and at 36 weeks' postmenstrual age. Odds ratios (ORs) were calculated and adjusted for any prenatal corticosteroid treatment, cesarean delivery, GA, infant sex, Apgar score at 10 minutes, and birth weight z score of less than -2. Results: In total, 7980 surfactant administrations were given to 5209 infants (2233 [42.9%] girls; 2976 [57.1%] boys): 629 (12.1%) born at full term, 691 (13.3%) at 32 to 36 weeks' GA, 1544 (29.6%) at 28 to 31 weeks' GA, and 2345 (45.0%) at less than 28 weeks' GA. Overall, 977 infants (18.8%) received off-label use. In 1364 of 3508 infants (38.9%) with GA of 22 to 31 weeks, the first administration of surfactant was given more than 2 hours after birth, and this was associated with higher odds of pneumothorax (adjusted OR [aOR], 2.59; 95% CI, 1.76-3.83), intraventricular hemorrhage grades 3 to 4 (aOR, 1.71; 95% CI, 1.23-2.39), receipt of postnatal corticosteroids (aOR, 1.57; 95% CI, 1.22-2.03), and longer duration of assisted ventilation (aOR, 1.34; 95% CI, 1.04-1.72) but also higher survival (aOR, 1.45; 95% CI, 1.10-1.91) than among infants treated within 2 hours of birth. In 146 infants (2.8%), the recommended maximum of 3 surfactant administrations was exceeded but without associated improvements in outcome. Omission of surfactant treatment occurred in 203 of 3551 infants (5.7%) who were receiving mechanical ventilation and was associated with lower survival (aOR, 0.49; 95% CI, 0.30-0.82). In full-term infants, 336 (53.4%) of those receiving surfactant had a diagnosis of meconium aspiration syndrome. Surfactant for meconium aspiration was not associated with improved neonatal outcomes. Conclusions and Relevance: In this study, adherence to best practices and labels for surfactant use in newborn infants varied, with important clinical implications for neonatal outcomes.

Cross-sectional study identifying high-alert substances in medication error reporting among Swedish paediatric inpatients.

AIM: The aims were to characterise paediatric medication errors and to identify the prevalence of known high-alert substances in these errors. METHODS: All paediatric drug-related incident reports and complaints nationally reported to the Health and Social Care Inspectorate in Sweden 2011-2017 regarding inpatients were characterised by context and modal details. In addition, drug use at a university hospital was matched to local incident reports. Drug substances were classified using three high-alert lists. RESULTS: On a national level, there were 160 reports (2.5 per 10 000 patients) in which the three high-alert lists were found in different degrees (17/35/47%). Morphine (n = 12), vancomycin (n = 11) and potassium (n = 7) were most frequently involved. Eighty per cent of the reports concerned patients aged 0-6 years. Intravenous was the most common route of administration (66%). On a university hospital level, the prevalence of all types of drug incidents reports was 1.7% among all inpatients. The prevalence of local incident reports involving high-alert substances was almost double that of non-alert substances. CONCLUSION: Existing high-alert drug lists are relevant for paediatric inpatients. A higher awareness and usage of such lists among hospital staff prescribing, dispensing and administering drugs to children may have the potential to reduce medication errors.

Drug Use and Type of Adverse Drug Events-Identified by a Trigger Tool in Different Units in a Swedish Pediatric Hospital.

PURPOSE: The objectives of our study were to determine drug use, type and incidence of all adverse event associated with drug or drug-related processes (Adverse Drug Events, ADE) among pediatric inpatients in relation to hospital unit and length of stay. PATIENTS AND METHODS: 600 pediatric (0-18 years) admissions at a Swedish university hospital during one year were included and stratified in blocks to 150 neonatal, surgical/orthopedic, medicine and emergency-medicine unit admissions, respectively. Adverse events were identified from medical records using a pediatric trigger tool. All triggers identifying an adverse event related to drugs and drug-related devices were included. Data on drug use were extracted from the hospital drug-data warehouse. RESULTS: In total, 17794 daily drug orders were administrated to 486 (81.0% exposed) admissions. Parental nutrition, potassium salts and morphine constituted half of all high-risk drugs prescribed. Two-thirds of intravenous irritating drug doses consisted of vancomycin, esomeprazole and meropenem. In 129 (21.5%) admissions, at least one ADE was identified, out of which 21 ADE were classified as more severe (National Coordinating Council Medication Error Reporting Prevention-Index, NCCMERP≥F). The ADE incidence was 47.4 (95% confidence interval: 39.4-57.3) per 1000 admission days and varied by unit category. In neonatal units, 56.9 (49.5-65.4) ADEs/1000 admission days were detected, in surgery/orthopedic 54.2 (40.3-72.8), in medicine 44.1 (33.1-58.7), and in emergency-medicine 14.3 (7.7-26.7) ADEs/1000 admission days were found. The most common types of ADEs were identified by triggers that were not directly aiming at drugs including insufficiently treated pain (incidence peaking already in the first days), skin, tissue or vascular harm (peaking at the end of the first week) and hospital-acquired infections (peaking in later admission days). CONCLUSION: Adverse drug events are common in pediatric patients. The incidence of ADEs and type of ADE varies by hospital unit and length of hospital stay.

Pediatricians' Understanding and Experiences of an Electronic Clinical-Decision-Support-System.

OBJECTIVES: Subsequent dosing errors after implementing an Electronic Medical Record (EMR) at a pediatric hospital in Sweden led to the development, in close collaboration with the clinical profession, of a Clinical Decision Support System (CDSS) with Dose Range Check and Weight Based Dose Calculation integrated directly in the EMR. The aim of this study was to explore the understanding and experiences of the CDSS among Swedish pediatricians after one year of practice. METHODS: Semi-structured interviews with physicians at different levels of the health care system were performed with seventeen pediatricians working at three different pediatrics wards in Stockholm County Council. The interviews were analysed with a thematic analysis without pre-determined categories. RESULTS: Six categories and fourteen subcategories emerged from the analysis. The categories included the use, the benefit, the confidence, the situations of disregards, the misgivings/risks and finally the development potential of the implemented CDSS with Weight Based Dose Calculation and Dose Range Check. CONCLUSIONS: A need for CDSS in the prescribing for children is evident to support the prevention of medication errors. After implementing a CDSS, organized efforts are crucial to understand the need for further development based on the practical knowledge of the clinical profession. Different contextual settings of health care organisations do affect the way how physicians think and act in work. When implementing a CDSS in practice we need to describe and analyse the context where the CDSS should be used as well as the prescribers' needs in work.

Dalteparin-sodium induced drug fever in a neonate.

Drug fever caused by dalteparin-sodium (DS), a low-molecular-weight derivative of heparin, is neither listed in the official drug information and nor published as a case report until today. A preterm infant, born at 26 weeks of gestation, developed fever 2 days after starting a treatment with DS for an intracardial thrombus. The fever reverses soon after changing the treatment to unfractionated heparin and reappeared after reintroduction of DS. Once again, after discontinuing DS, the infant regained normothermia. Bacterial and viral infections, tissue damage, impaired liver or kidney function, preservative agents and comedications could be ruled out as fever origin. By using the Naranjo adverse drug reaction (ADR) probability scale and the Liverpool ADR causality assessment tool, this case can be classified as 'probable ADR' and 'definite ADR'. This is the first case report of a drug fever caused by the low-molecular-weight heparin DS in a preterm infant.

Validation of triggers and development of a pediatric trigger tool to identify adverse events.

BACKGROUND: Little is known about adverse events (AEs) in pediatric patients. Record review is a common methodology for identifying AEs, but in pediatrics the record review tools generally have limited focus. The aim of the present study was to develop a broadly applicable record review tool to identify AEs in pediatric inpatients. METHODS: Using a broad literature review and expert opinion with a modified Delphi process, a pediatric trigger tool with 88 triggers, definitions, and descriptions including AE preventability decision support was developed and tested in a random sample of 600 hospitalized pediatric patients admitted in 2010 to a single university children's hospital. Four registered nurse-physician teams performed complete two-stage retrospective reviews of 150 records each from either neonatal, surgical/orthopedic, medicine, or emergency medicine units. RESULTS: Registered nurse review identified 296 of 600 records with triggers indicating potential AEs. Records (n = 121) with only false positive triggers not indicating any potential AEs were not forwarded to the next review stage. On subsequent physician review, 204 (34.0%) of patients were found to have had 563 AEs, range 1-27 AEs/patient. A total of 442 preventable AEs were found in 161 patients (26.8%), range 1-22. Overall, triggers were found 3,598 times in 417 (69.5%) records, with a mean of 6 (median 1, range 0-176) triggers per patient. The overall positive predictive value of the triggers was 22.9%, (range 0.0-100.0%). The final pediatric trigger tool, developed with a second Delphi round, required 29 triggers. CONCLUSIONS: AEs are common in pediatric patients and most are preventable. The main contributions of this study are to further develop and adapt trigger definitions, including AE preventability decision support, to introduce new triggers in pediatric care, as well as to apply pediatric triggers in different clinical specialties. Our findings resulted in a national pediatric trigger tool, and might also be adapted internationally. The pediatric trigger tool can help healthcare organizations to measure and analyze the AEs occurring in hospitalized children in order to improve patient safety.

Exploring differences in inpatient drug purchasing cost between two pediatric hospitals.

OBJECTIVES: In this study, the hospital cost of purchasing drugs at two children's hospitals is explored with respect to high-cost drugs and drug classes and discussed with regard to differences in hospital setting, drug price, or number of treatments. METHODS: The purchasing costs of drugs at the two hospitals were retrieved and analyzed. All information was connected to the Anatomic Therapeutic Chemical code and compared in a Microsoft Access database. RESULTS: The 6-month drug purchasing costs at Astrid Lindgren Children's Hospital (ALCH), Stockholm, Sweden, and Lucile Packard Children's Hospital at Stanford (LPCH), Palo Alto, California, are similar and result in a cost per patient day of US $149 and US $136, respectively. The hospital setting and choice of drug products are factors that influence the drug cost in product-specific ways. CONCLUSIONS: Several problems are highlighted when only drug costs are compared between hospitals. For example, the comparison does not take into account the amount of waste, risk of adverse drug events, local dosing strategies, disease prevalence, and national drug-pricing models. The difference in cost per inpatient day at ALCH may indicate that cost could be redistributed in Sweden to support pediatric pharmacy services. Also, when introducing new therapies seen at the comparison hospital, it may be possible to extrapolate the estimated increase in cost.

Acid reducing agents to neonates - lack of evidence and guidelines.

OBJECTIVE: The aim of this retrospective study was to investigate the clinical practice, i.e. the frequency of use and the treatment strategies, for acid reducing drugs to neonates in a Swedish hospital. METHODS: Retrospective reviews of charts and interviews with nurses at the neonatal wards of Karolinska University Hospital were performed to identify difficulties that might occur with drug administration. All patients admitted over a 2-month period were included. Main outcome measure were the number of patients treated with acid reducing drugs and the dosages. RESULTS: Nine out of 215 patients (4.2%) received an acid reducing drug. Patients treated with acid reducing drugs had significantly lower birth weight, lower gestational age and longer duration of hospitalization. Eight of the patients were treated with omeprazole. One of these patients started treatment with omeprazole but continued later on with ranitidine. One patient was exclusively treated with ranitidine. The doses of omeprazole (intravenous or oral administration) were within the range 0.16-1.26 mg/kg/day. CONCLUSIONS: A wide variation in treatment regimens of acid reducing drugs is given to newborn infants. The percentage of treated children was much lower than earlier reports from the US and UK. No conclusions can be drawn as to whether the doses and dosing intervals used give sufficient acid suppression, since the effect of the therapy was not recorded. The present study is only retrospective and data are not truly comparable with other studies. Further studies are therefore warranted to evaluate effective doses and pharmacokinetics of acid reducing drugs in newborn infants.

Population pharmacokinetics of tacrolimus in pediatric liver transplantation: early posttransplantation clearance.

BACKGROUND: Tacrolimus is an immunosuppressant with a narrow therapeutic window, with considerable pharmacokinetic variability. Getting sufficient concentrations in pediatric liver transplantation is imperative, but it has proven difficult in the immediate posttransplantation period in particular. A predictive pharmacokinetic model could be the basis for development of a novel initial dose schedule, and therapeutic drug monitoring with Bayesian methodology. METHODS: The predictive capacity of 2 previously developed population pharmacokinetic models of tacrolimus in pediatric liver transplant recipients was tested in 20 new patients using Bayesian forecasting. Predictive performance was poor in the immediate posttransplant period with tacrolimus pharmacokinetics changing rapidly. A new population pharmacokinetic model, focusing on the immediate posttransplant period, was subsequently developed in 73 patients. RESULTS: An increase in the apparent clearance of tacrolimus in the first few weeks after transplant was evident. Typical apparent clearance of tacrolimus was 0.148 L·h(-1)·kg(-0.75) immediately after transplantation, increasing to a maximum of 1.37 L·h(-1)·kg(-0.75). Typical apparent distribution volume was 27.2 L/kg. Internal and external validation studies confirmed the predictive capabilities of the developed model. Simulation studies reveal that in 60% of subjects the current initial standard dose without subsequent dosage adjustments overshoot the desired trough concentration range of 10-20 ng/mL. An alternative dosing schedule was developed based on allometric scaling with an initial loading dose followed by a maintenance dose increasing with time. CONCLUSIONS: A population pharmacokinetic model for tacrolimus was developed, to better describe the early posttransplantation phase. This model has the potential to aid therapeutic drug monitoring and was also used to suggest a revised dosing scheme in the intended population.

Off-label drug use evaluation in paediatrics--applied to ciprofloxacin when used as treatment of cholangitis.

PURPOSE: To evaluate drug and indication specific off-label use in paediatrics, applied to ciprofloxacin (CPFX) in cholangitis. METHODS: We collected four different sets of data for an off-label drug use evaluation. (1) Literature review from medical journals, (2) the use and safety profile from the whole Swedish paediatric population by extracting data from national registers, (3) locally performed retrospective drug chart reviews, and (4) interviews regarding paediatric patients with CPFX treated cholangitis. RESULTS: The literature reviews show a lack of information for paediatric use of CPFX in cholangitis. The prescribing of CPFX to Swedish children has grown over the last decade and generated a small number of reports for adverse drug reactions. In our local biliary atresia population 32 patients had suffered from at least one episode of cholangitis and 13 patients had been prescribed CPFX. The dosing strategy had an empirical prescribing approach, since monitoring of bacterial resistance and efficacy is difficult in the biliary ducts. No clear relationship was seen between dosing and age/weight. Reports of suspected side effects could not be found in the retrospective chart reviews. The interviews show that the existing dosage forms are well accepted. CONCLUSIONS: This drug use evaluation creates awareness of the off-label situation. The international and national data are sparse for the paediatric use of CPFX in cholangitis. Locally we have highlighted a heterogeneous dosing strategy of CPFX, drug/drug interactions, and the need to monitor and report the risk of short- and long-term adverse drug reactions.

Over-the-counter drug use--estimations within the Swedish paediatric population.

We have used three different sources to estimate the use of drugs sold over the counter (OTC) by the Swedish paediatric population during 2007-2008 as part of a European evaluation initiated by the European Medicines Agency. An estimation of the paediatric use from the total numbers of over-the-counter drugs (OTCD) packages sold by Swedish pharmacies and analyses of two separate questionnaires directed towards a population of 11- to 14-year-old children and another towards visitors to one of the paediatric emergency wards in Stockholm County were included in the study. In Sweden, 1.25 OTC packages are sold quarterly per child (0-18 years), and the children in both questionnaire studies use, on average, 0.9 OTC substances. Sixty-five percent of the children visiting an emergency ward and 67% of the 13-year-old Stockholm inhabitants had used at least one OTCD. OTCD use among children is common. Interpretation of OTCD data must be done carefully since questions with regard to OTCD use is subject to recall bias and the number of packages sold to children is hypothesised through a conversion factor.

Transfer of buprenorphine into breast milk and calculation of infant drug dose.

Little is known about the safety of buprenorphine (BUP) in breastfeeding. The aim of this work was to investigate the transfer of buprenorphine and its main active metabolite, norbuprenorphine (n-BUP), into human milk and to determine the drug dose and effects in exposed infants. Seven lactating women, who were maintained on BUP treatment because of previous opiate addiction, were studied in an open observational study. All mothers had a strong wish to breastfeed their newborn infants. Buprenorphine samples for analysis were collected from the urine of 6 infants together with breast milk, blood, and urine from their mothers during a 24-hour period in the week after birth. One mother-infant pair was studied at 9 months of age. Buprenorphine and n-BUP were analyzed by a liquid chromatography/mass spectrometry method suitable for handling different matrices. Buprenorphine and n-BUP were found in low levels in the infants' urine. Breastfed infants were exposed to a calculated BUP dose per kg bodyweight less than 1%, with an average milk/plasma area under the curve of 1.7 (range, 1.1-2.8) for BUP and 0.7 (range, 0.4-1.2) for n-BUP. These data support the use of BUP during breastfeeding. However, the authors recommend that infants be monitored closely.

Chitosan as a carrier for non-viral gene transfer in a cystic-fibrosis cell line.

The gene transfer mediated by chitosan in CFBE41o(-) (a cystic-fibrosis bronchial epithelial cell line) and HEK (a human embryonic kidney cell line) has been evaluated. Polyplexes based on chitosan and PEI (polyethyleneimine) using a luciferase and enhanced green fluorescent protein reporter plasmid showed that the transfection efficacy of polyplexes in the CFBE41o(-) cell line was poor compared with that in HEK cells. In the highly differentiated cystic-fibrosis bronchial epithelial cell line the narrow-size-distributed chitosan shows enhanced transfection at a low pH compared with PEI. The enhanced transfection at lower pH could be a result of damage to the cell surface or changes in the cell-surface charge, leading to better penetration of the cell membrane.