Ursula Gundert-Remy

Optimizing pharmacotherapy is a central goal of clinical pharmacology

Background/Objectives: 5-fluorouracil (5-FU) is used in the treatment of solid cancer types. Because of its narrow therapeutic window, drug monitoring is recommended. We were confronted to answer a question on the relevance of concentration as opposed to the area under the plasma concentration–time curve (AUC) to predict toxicity when we had to assess the case of a patient who died after an erroneously high infusion rate. Methods: We used physiologically-based pharmacokinetic modeling (PBPK) to simulate the concentration–time profile of 5-FU data on doses, dosing schedules and life-threatening toxicity for both the patient in question as well as data from the literature. Furthermore, steady-state 5-FU concentrations were calculated from an additional set of data found in the literature on AUCs and non-life-threatening toxicity. Results: The model predictions matched well with experimental data, confirming the suitability of the model. Life-threatening toxicity was related to a concentration above 6 mg/L, whereas non-life-threatening toxicity was low at concentrations less than 3 mg/L but steeply increased between 3 and 4 mg/L. Data analysis supported by a decision algorithm suggests that the 5-FU steady-state plasma concentration is a better toxicity predictor than the AUC. Conclusions: We recommend monitoring the concentration one hour after infusion starts when about 50% of the steady state is reached in patients for whom higher doses are clinically considered relevant. Monitoring the concentration one hour after starting the infusion has the advantage that dose correction could be made early before toxicity can be observed.

The present opinion is the follow‐up of the conclusions and recommendations of the Scientific Opinion on the re‐evaluation of silicon dioxide (E 551) as a food additive relevant to the safety assessment for all age groups. In addition, the risk assessment of silicon dioxide (E 551) for its use in food for infants below 16 weeks of age is performed. Based on the newly available information on the characterisation of the SAS used as E 551 and following the principles of the 2021 EFSA Guidance on Particle‐TR, the conventional safety assessment has been complemented with nano‐specific considerations. Given the uncertainties resulting from the limitations of the database and in the absence of genotoxicity concern, the Panel considered that it is not appropriate to derive an acceptable daily intake (ADI) but applied the margin of exposure (MOE) approach for the risk assessment. The Panel concluded that the MOE should be at least 36 for not raising a safety concern. The calculated MOEs considering the dietary exposure estimates for all population groups using the refined non‐brand loyal scenario, estimated at the time of the 2018 re‐evaluation, were all above 36. The Panel concluded that E 551 does not raise a safety concern in all population groups at the reported uses and use levels. The use of E 551 in food for infants below 16 weeks of age in FC 13.1.1 and FC 13.1.5.1 does not raise a safety concern at the current exposure levels. The Panel also concluded that the technical data provided support an amendment of the specifications for E 551 laid down in Commission Regulation (EU) No 231/2012. The paucity of toxicological studies with proper dispersion protocol (with the exception of the genotoxicity studies) creates uncertainty in the present assessment of the potential toxicological effects related to the exposure to E 551 nanosize aggregates.

PFASs are defined as substances that contain at least one fully fluorinated methyl (CF₃–) or methylene (–CF₂–) carbon atom. The excellent technical properties of members of the PFAS group have led to their use in a wide range of applications. The substance group comprises more than 10,000 individual compounds. A variety of adverse effects has been described for single substances. For the majority of the PFASs, neither toxicokinetic data nor effect data is available. Hence, because of the small number of PFASs for which a full toxicological profile is available, grouping based on the existing data is not feasible. A critical problem of PFASs and their degradation products is the very high persistence, which clearly fulfils the criterion for the substance property Very Persistent (vP) according to Annex XIII of the REACH Regulation. Because of this property the European Commission is planning to take action. Defining suitable subgroups appears to be a scientifically based approach. However, to reach this goal, large data gaps would have to be closed which would take up to centuries, a time-frame, which is not defendable with respect to potential irreversible harm. Because of the time pressure resulting from the potential irreversible harm, the precautionary principle has been selected as an appropriate tool to handle PFASs and in the restriction proposal PFASs are treated as one group. This approach is justified in the view of the advisory committee of the German Society for Toxicology. ECHA’s proposal received a lot of attention in the public. However, communication so far has obviously led to the misunderstanding of a proven health hazard for all PFASs. Communication should explain the justification of the broad inclusion of substances as being based on the precautionary principle. Data gaps versus current knowledge need to be clearly communicated; communication should also include the possibility for derogation of essential use. It should address the issue of suitable substitutes to avoid unintended health consequences; and it should mention that existing persistent environmental contamination calls for developing innovation in remediation techniques.

Infants of mothers treated for tuberculosis might be exposed to drugs via breast milk. The existing information on the exposure of breastfed infants lacks a critical review of the published data. We aimed to evaluate the quality of the existing data on antituberculosis (anti-TB) drug concentrations in the plasma and milk as a methodologically sound basis for the potential risk of breastfeeding under therapy. We performed a systematic search in PubMed for bedaquiline, clofazimine, cycloserine/terizidone, levofloxacin, linezolid, pretomanid/pa824, pyrazinamide, streptomycin, ethambutol, rifampicin and isoniazid, supplemented with update references found in LactMed^®. We calculated the external infant exposure (EID) for each drug and compared it with the recommended WHO dose for infants (relative external infant dose) and assessed their potential to elicit adverse effects in the breastfed infant. Breast milk concentration data were mainly not satisfactory to properly estimate the EID. Most of the studies suffer from limitations in the sample collection, quantity, timing and study design. Infant plasma concentrations are extremely scarce and very little data exist documenting the clinical outcome in exposed infants. Concerns for potential adverse effects in breastfed infants could be ruled out for bedaquiline, cycloserine/terizidone, linezolid and pyrazinamide. Adequate studies should be performed covering the scenario in treated mothers, breast milk and infants.