## 2 Commonly Used Pharmaceuticals: Their Classes, Chemical Structures, and Therapeutic Applications  
Approximately 3000 pharmaceutical substances are used in the European Union. The most widely used molecules are antibiotics for human and veterinary medicine, their consumption has reached 12,500 tons per year over the last decade. Non-steroidal anti-inflammatory drugs (NSAIDs) such as acetylsalicylic acid (aspirin), diclofenac, and ibuprofen are inhibitors of the two isoforms of cyclo-oxygenase (cox-1 and cox-2) enzymes, involved in prostaglandin synthesis. Ibuprofen, scientifically named 4-isobutylphenyl-2-propionic acid, is one of the most widely used NSAIDs worldwide. Additionally, there are other types of drugs, such as analgesics like paracetamol, that are considered antipyretic (Table 1). It appears to inhibit cyclo-oxygenase in the central nervous system without peripheral action, which is the reason why it does not have anti-inflammatory effects. Naproxen (NPX) is one of the most effective analgesics, a non-steroidal anti-inflammatory drug (NSAID), and it has been found in both surface water and wastewater at concentrations ranging from 20 ng/L to several mg/L [22]. Additionally, it is detected in wastewater treatment plants in the range of 250 to 1.5 ug/L, and its removal has been estimated at around 71% [23]. NPX has an excellent cardiac profile; however, it has been reported that people who ingest trace amounts of NPX have a higher risk of heart attack or a higher potential of urinary bladder cancer [24; 25; 26]. Depending on the development of their health services, the type and the concentration of drugs in sewage systems vary in each country. As an example, in Table 1, major pharmaceutical products used in Tunisia are shown with a predominance of antibiotics and analgesics. In Northern countries, synthetic and natural hormones, such as 17-\(\alpha\)-ethinylestradiol (EE2) and 17-\(\beta\)-estradiol (E2), are present in wastewater at a non-negligible level [27]. \begin{table}
\begin{tabular}{c c c c c} \hline
**Class** & **Pharmaceuticals** & **Chemical Formula** & **Molecular Weight g/mol** & **Uses** & **Structure** \\ \hline Analogsic/antipyretic & Acataminophen & C\({}_{4}\)H\({}_{8}\)NO\({}_{2}\) & 151.16 & Used for mild-to-moderate pain and fever. & \\ \hline Aspirin & C\({}_{4}\)H\({}_{8}\)O\({}_{4}\) & 180.16 & Used in the prevention of arterial and venous thrombosis. & \\ \hline Lamettigine & C\({}_{4}\)H\({}_{8}\)CN\({}_{5}\) & 256.09 & Used antiscure medication that is a rare but well-known cause of idiosyncratic liver injury that can be severe and even fatal. & \\ \hline Tamandol & C\({}_{4}\)H\({}_{82}\)NO\({}_{2}\) & 263.37 & Used as a narcticle analysis for severe pain. & \\ \hline Antibiotic & Amoxicillin & C\({}_{82}\)H\({}_{82}\)NO\({}_{5}\)S & 365.4 & Used in the treatment of mild-to-moderate bacterial infections such as mastitis, bronchitis, otitis media, otolitis, and community acquired pneumonia. & \\ \hline Asithromycin & C\({}_{82}\)H\({}_{82}\)NO\({}_{2}\) & 749 & Related for the rare instances of acute liver injury. & \\ \hline Davonbici & C\({}_{2}\)H\({}_{82}\)NO\({}_{4}\) & 543.5 & Used in the therapy of several forms of lymphoma, leukemia, sarcoma, and solid organ cancers. & \\ \hline Ciprofloxacin & C\({}_{2}\)H\({}_{82}\)PN\({}_{5}\)O\({}_{5}\) & 331.54 & Used in the therapy of mild-to-moderate urinary and respiratory tract infections caused by susceptible organisms. & \\ \hline Metronidazole & C\({}_{4}\)H\({}_{82}\)NO\({}_{5}\) & 172.15 & Used in the treatment of many anaerobic and certain protovacon and parasitic infections. & \\ \hline \end{tabular}
\end{table} 
Table 1: Class and chemical structure of the most used pharmaceutical products in Tunisia.