Paracetamol overdosing in a tertiary care hospital: implementation and outcome analysis of a preventive alert programme

WHAT IS KNOWN AND OBJECTIVES

Paracetamol is a frequently used antipyretic and analgesic drug, but also a dose-dependent hepatotoxin. Unintentional paracetamol overdosing is a common medication error in hospitals. The present study aimed at (i) analysis of unintentional paracetamol overdosing in hospitalized patients; (ii) development, implementation and outcome analysis of an alert algorithm for the prevention of relevant paracetamol overdosing.

METHODS

All patients who received paracetamol in a Swiss tertiary care hospital during 2011 to 2014 were analysed to detect cases of paracetamol overdosing in a local pharmacoepidemiological database. In 2014, an automated algorithm screened the hospital's electronic prescribing system for patients at risk of overdosing, followed by expert validation. When imminent relevant overdosing was confirmed, alerts were issued to prescribers. Relevance was defined as prescriptions that permitted repeated daily paracetamol exposure of ≥5 g.

RESULTS AND DISCUSSION

From 2011 to 2013, relevant overdosing occurred in 11 patients (5-8 g/day for 3 to 5 days), which corresponds to 0·4 % of all patients exposed to any paracetamol overdosing (mean n = 988 per year). In 2014, alerts were issued by experts in 23 cases with subsequent changes to prescriptions in 21 (91·3 %) thereof. Although the occurrence of any paracetamol overdosing declined only marginally in 2014 (n = 914), no relevant overdosing occurred anymore.

WHAT IS NEW AND CONCLUSION

Unintentional paracetamol overdosing was frequent but only a small fraction thereof was deemed relevant. This proof of concept study analysed local hospital data and developed a preventive system combining sensitive automated detection with subsequent specific expert validation. The resulting alerts achieved high compliance and prevented relevant paracetamol overdosing.

Evaluation of drug interactions in a large sample of psychiatric inpatients: a data interface for mass analysis with clinical decision support software

In order to improve medication safety, more epidemiological data on the prevalence and clinical relevance of drug interactions are required. We developed an interface for mass analysis using the Clinical Decision Support Software (CDSS) MediQ and a multidimensional classification (Zurich Interaction System (ZHIAS)) incorporating the Operational Classification of Drug Interactions (ORCA). These were applied to 359,207 cross-sectional prescriptions from 84,607 psychiatric inpatients collected through the international AMSP program. MediQ issued 2,308 "high" and 71,112 "average" danger interaction alerts. Among these, after ORCA reclassification, there were 151 contraindicated and 4,099 provisionally contraindicated prescriptions. The ZHIAS provided further detailed categorical information on recommended management and specific increased risks (QTc prolongation being the most frequent one) associated with interactions. We developed a highly efficient solution for the identification and classification of drug interactions in large prescription data sets; this solution may help to reduce the frequency of overalerting and improve acceptance of the efficacy of CDSS in reducing the occurrence of potentially harmful drug interactions.

Pharmacokinetics and pharmacodynamics of cinacalcet in patients with hyperparathyroidism after renal transplantation

Cinacalcet is a calcimimetic drug for the treatment of secondary hyperparathyroidism (HPT). In a sequential open-label study, ten patients with persistent HPT after renal transplantation received first 30 and then 60 mg oral cinacalcet once daily over 2 weeks each. Cinacalcet steady state oral clearance was 131.1 +/- 20.9 l/h and 92.8 +/- 9.5 l/h (mean +/- SE) after 30 and 60 mg, respectively. Cinacalcet and parathyroid hormone (PTH) concentrations showed an inverse correlation and were fitted to a simple E(max) model (E(max) = 80% reduction vs. baseline, EC(50) = 13 ng/mL). A once daily administration of cinacalcet lowered serum calcium over 24 h without fluctuations. The 8-h fractional urinary excretion of calcium was increased after 60 mg cinacalcet (baseline 0.85 +/- 0.17%, 30 mg 1.53 +/- 0.35%, 60 mg 1.92 +/- 0.37%). Renal function remained stable. Cinacalcet pharmacokinetics and pharmacodynamics showed a pronounced interindividual variability. We conclude that the once daily administration of cinacalcet in patients with secondary HPT after renal transplantation effectively reduced iPTH and serum calcium. The transient calciuria could potentially favor nephrocalcinosis and reduce bone mineral density, suggesting that higher doses of cinacalcet need to be used with caution in renal transplant recipients with severe persistent hyperparathyroidism.

Decreased glutathione in patients with anorexia nervosa. Risk factor for toxic liver injury?

OBJECTIVE

To investigate glutathione and amino acids related to glutathione metabolism in patients with anorexia nervosa in order to test the hypothesis that these patients exhibit a deficiency of glutathione and therefore might be at an increased risk of developing toxic liver injury.

DESIGN

Controlled observatory study and case report.

SETTING

University Hospital.

SUBJECTS

Subjects included 11 female patients with anorexia nervosa and 12 healthy female controls.

INTERVENTIONS

Determination of fasting free and total glutathione, homocysteine, vitamins B(6) and B(12) and folic acid in plasma.

RESULTS

A 14-y-old patient with a body mass index of 12.6 kg/m(2) presented with markedly elevated transaminases (ALAT >50 x upper limit of normal), and paracetamol was detected in her blood. Patients with anorexia nervosa exhibited lower circulating concentrations of free cysteine (8.9+/-1.5 vs 12.0+/-1.4 micromol/l) and free and total glutathione (5.0+/-1.3 vs 7.1+/-1.2 and 11.2+/-3.8 vs 16.2+/-5.0 micromol/l, respectively). The plasma concentrations of homocysteine (17.5+/-4.9 vs 12.0+/-3.8 micromol/l) and also of glycine (194+/-37 vs 143+/-41 micromol/l) and glutamine (422+/-51 vs 353+/-51 micromol/l) were significantly higher in patients with anorexia nervosa who were not deficient in folic acid, vitamin B(6) and B(12).

CONCLUSIONS

Lower plasma concentrations of glutathione suggest lower intracellular concentrations of the tripeptide. Higher homocysteine, glycine and glutamine concentrations point to a decreased utilization of these amino acids for glutathione synthesis and an impairment of trans-sulfuration. Consequently, the capacity of patients with anorexia nervosa to detoxify electrophilic metabolites and reactive oxygen species via glutathione may be impaired.

Effect of lysine clonixinate on the pharmacokinetics and anticoagulant activity of phenprocoumon

The effect of the non-steroidal anti-inflammatory drug lysine clonixinate ([2-(3-chloro-o-toluidino)nicotinic acid]-L-lysinate, CAS 55837-30-4) on the pharmacokinetics and anticoagulant activity of phenprocoumon (4-hydroxy-3-(1-phenylpropyl)-coumarin, CAS 435-97-2) was investigated in an open, randomised, two-fold, cross-over study in 12 healthy male volunteers. These subjects received a single dose of 18 mg phenprocoumon without or with concomitant treatment with lysine clonixinate (125 mg five times a day for 3 days before and 13 days after ingestion of a single dose of phenprocoumon). Pharmacokinetic parameters of phenprocoumon following oral administration were: CL/f: 0.779 +/- 0.157 ml/min, half-life of elimination: 147.2 +/- 19.9 h; free fraction in serum: 0.51 +/- 0.20%. These parameters were not significantly altered by concomitant treatment with lysine clonixinate. Prothrombin time increased from 13.3 +/- 1.3 s (at time 0) to 17.7 +/- 2.7 s following phenprocoumon and from 13.3 +/- 1.2 s to 18.0 +/- 2.2 s following combined administration. Prothrombin time returned to the pretreatment values 240 h after administration of phenprocoumon. The integrated effect (AUEC0-288 h) was identical following both treatments (4.303 +/- 461 and 4.303 +/- 312 s x h for phenprocoumon alone and phenprocoumon with lysine clonixinate, respectively). Thus, lysine clonixinate administered in therapeutic doses does not affect the pharmacokinetics and anticoagulant activity of phenproxoumon.

Veno-occlusive disease, nodular regenerative hyperplasia and hepatocellular carcinoma after azathioprine treatment in a patient with ulcerative colitis

We report the case of a 66-year-old male with ulcerative colitis diagnosed in 1987, who had been treated with azathioprine (AZA) for the past two years (average dose about 1.6 mg/kg/day). In May 1999 he presented with painless jaundice, fatigue and recent weight loss. Cholestatic enzymes were elevated, alpha-fetoprotein was normal and hepatitis B/C serology negative. After diagnosis of veno-occlusive disease (VOD) and hepatocellular carcinoma (HCC) via biopsy, tumour resection was performed. The histology was typical for a well-differentiated HCC with trabecular and pseudoglandular structures. Neighbouring liver tissue was atrophic, with nodular regenerative hyperplasia (NRH), peliosis-like sinusoidal ectasias and intra-sinusoidal accumulation of blood, associated with peri-sinusoidal fibrosis. Although none of the well-established risk factors for HCC such as cirrhosis, hepatitis B/C, metabolic liver disease or toxins were present, this patient developed HCC. This and previous reports suggest that NRH and/or VOD associated with AZA represent a risk factor for HCC. AZA should therefore not only be stopped in patients with NRH/VOD but patients should also be screened for HCC.

Age-dependent differences in the anticoagulant effect of phenprocoumon in patients after heart valve surgery

OBJECTIVE

An enhanced response to warfarin and an increased risk of major bleeding has been observed in older patients. The reason for this increase in sensitivity remains unknown. It could be due to pharmacodynamic reasons, pharmacokinetic reasons, or both.

METHODS

We therefore followed an anticoagulant regimen with phenprocoumon in 19 older (76 years) and 19 younger patients (50 years) following heart valve replacement. INR values were determined frequently. At the 4th and around the 24th day after starting treatment with phenprocoumon, we also measured the total and unbound plasma concentration of phenprocoumon.

RESULTS

The dose requirement to obtain the desired anticoagulant effect was significantly lower in the older patients than in the younger patients (26.3 vs. 37.3 micrograms.kg-1.day-1). The total plasma concentration (2.19 vs. 2.43 micrograms.ml-1), the percentage unbound drug in the plasma (0.61 vs. 0.64%) and the unbound plasma concentration (13.8 vs. 15.1 ng.ml-1) did not differ significantly between older and younger patients. The dose-adjusted INR (INR/dose) was higher in the older patients (110 vs. 67) but the INR adjusted for the unbound plasma concentration (INR/Cuss) which reflects the intrinsic sensitivity to the drug, was not significantly different (192 vs. 173). However, the older patients had an about 30% significantly lower metabolic clearance based on unbound drug (84 vs. 115 ml.kg-1.h-1).

CONCLUSIONS

Older patients (> 70 years) require a dose approximately 30% lower than younger patients (< 160 years). Pharmacokinetic reasons (reduced metabolic clearance) are mainly responsible for the lower dose requirement of the older patients after heart valve surgery.