I am calculating the PEC for selected antibiotic compounds and am having problems finding the readily-available online data about the Fexcreta value for my target compounds (Since the PEC calculation needs Fexcreta value). However, I found this statement online:
"Cephalexin is excreted in the urine by glomerular filtration and tubular secretion. Studies showed that over 90% of the drug was excreted unchanged in the urine within 8 hours. During this period, peak urine concentrations following the 250 mg, 500 mg, and 1 g doses were approximately 1000, 2200, and 5000 mcg/mL respectively. "
Does it mean that Fexcreta for cephalexin is 0.9?
Please look at the following below links which may help you in your analysis:
http://eeer.org/upload/eer-2019-405.pdf
https://hal.archives-ouvertes.fr/hal-02868010/document
https://pubmed.ncbi.nlm.nih.gov/30666572/
Thanks
Fexcreta value for Select Antibiotics?
Response: I coudn't resist my curiosity and therefore have presented the following for your reference. You seem to be one of the few who could perhaps provide some insight into this still unclear understanding.
A number of authors have reported significant quantities of and their occurrence in aquatic systems as humans consume appreciable quantities. Environmental risk assessment therefore becomes evident as they are discharged into surface waters through Sewage Treatment Plants (STPs).
I find that majority of studies of antibiotics removal via tertiary wastewater treatment have been conducted in EU nations, the USA, Australia, and China. However, a large discrepancy of removal efficiencies is apparent across different studies of these treatment processes as increases in antibiotics concentration following tertiary treatment (Chlorination) have also been observed and in comparison, sand filtration and UV irradiation are less effective which, may be because of sorption to filtered particles, sampling strategies, specific operating parameters of wastewater treatment plants and DE conjugation. Tertiary treatment therefore is concluded to be still arguable on antibiotic removal efficiency when sampling wastewater in full-scale WWTPs.
There has been research of measuring through best approach Predicted Environmental Concentrations (PECs) after refinement to Measured Environmental Concentrations (MECs) under European Medicines Agency (EMA) and also to predicted no-effect concentrations (PNECs). The risk quotient between PECs and PNECs was found higher than 1 for about twelve pharmaceuticals indicating risk to all three trophic levels of aquatic organisms – algae, dophnids and fish. This is against default value of penetration factor (Fpen) under EMA whidh is 0.01. When we incorporate consumption and excretion data changing the default value of Fpen to 0.04 and adding safety factor of 10 which need be performed for pharmaceuticals already on the market as for example, ERA framework, it suggests that ERA should incorporate a risk-benefit analysis.
In a case study on conventional biological treatment plant, focussing on eleven drugs representative of therapeutic classes – measured environmental concentrations (MECs) ranged from low ng 1 to 1.5 in effluent and to a few hundred ng L-1 in receiving surface waters which showed good agreement between MEC and PEC for seven of the chosen eleven samples. However, no such match between PEC and MEC indicating limitations of the approach.
We find literature for environmental endpoint data on 22 pharmaceuticals which is not difficult for retrieval. The Swedish Environmental Classification contains information on 15 out of 22 select pharmaceuticals. For two of the chemicals – amoxicillin and etinylestradiol – PEC/PNEC ratios calculated showed above 1 – to evaluate actual risks, an extended environmental fate and effect analysis is warranted.
In the light of the limited data available, it is evident that more environmental endpoint results are warranted which will make it easier to calculate PNECs for more pharmaceuticals. Accordingly, WHO has directed focus on developing methods or protocols for prioritizing pharmaceuticals with respect to risk assessment for drinking water hazards.
I do not know how to share the flow diagram. Please suggest.
Isam Eldin Hussein Elgailani : Thank you for the references!
A K Shyam : Helpful and insightful points have been made. In my study, the scope is only limited to conventional WWTP systems as a fixed variable. However, most of your points have given me ideas on structuring my research content. For the flow diagram, you can share through the 'add files' with a paperclip icon button below the answering box. I have gained important inputs nevertheless from your response, I appreciate the explanations.
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