The evolution of the class of antibacterial quinolones includes the introduction in therapy of highly successful compounds. Although many representatives were withdrawn due to severe adverse reactions, a few representatives have proven their therapeutical value over time. The classification of antibacterial quinolones into generations is a valuable tool for physicians, pharmacists, and researchers. In addition, the transition from one generation to another has brought new representatives with improved properties. In the last two decades, several representatives of antibacterial quinolones received approval for therapy. This review sets out to chronologically outline the group of approved antibacterial quinolones since 2000. Special attention is given to eight representatives: besifloxacin, delafoxacin, finafloxacin, lascufloxacin, nadifloxacin and levonadifloxacin, nemonoxacin, and zabofloxacin. These compounds have been characterized regarding physicochemical properties, formulations, antibacterial activity spectrum and advantageous structural characteristics related to antibacterial efficiency. At present these new compounds (with the exception of nadifloxacin) are reported differently, most often in the fourth generation and less frequently in a new generation (the fifth). Although these new compounds’ mechanism does not contain essential new elements, the question of shaping a new generation (the fifth) arises, based on higher potency and broad spectrum of activity, including resistant bacterial strains. The functional groups that ensured the biological activity, good pharmacokinetic properties and a safety profile were highlighted. In addition, these new representatives have a low risk of determining bacterial resistance. Several positive aspects are added to the fourth fluoroquinolones generation, characteristics that can be the basis of the fifth generation. Antibacterial quinolones class continues to acquire new compounds with antibacterial potential, among other effects. Numerous derivatives, hybrids or conjugates are currently in various stages of research.

The emergence of bacterial resistance has motivated researchers to discover new antibacterial agents. Nowadays, fluoroquinolones keep their status as one of the essential classes of antibacterial agents. The new generations of fluoroquinolones are valuable therapeutic tools with a spectrum of activity, including Gram-positive, Gram-negative, and atypical bacteria. This review article surveys the design of fluoroquinolone hybrids with other antibacterial agents or active compounds and underlines the new hybrids’ antibacterial properties. Antibiotic fluoroquinolone hybrids have several advantages over combined antibiotic therapy. Thus, some challenges related to joining two different molecules are under study. Structurally, the obtained hybrids may contain a cleavable or non-cleavable linker, an essential element for their pharmacokinetic properties and mechanism of action. The design of hybrids seems to provide promising antibacterial agents helpful in the fight against more virulent and resistant strains. These hybrid structures have proven superior antibacterial activity and less susceptibility to bacterial resistance than the component molecules. In addition, fluoroquinolone hybrids have demonstrated other biological effects such as anti-HIV, antifungal, antiplasmodic/antimalarial, and antitumor activity. Many fluoroquinolone hybrids are in various phases of clinical trials, raising hopes that new antibacterial agents will be approved shortly.

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Objective: The compatibility of four binary active substances combinations adapalene – levofloxacin (ADP-LFX), adapalene – miconazole nitrate (ADP-MCZ), levofloxacin – meloxicam (LFX-MLX) and levofloxacin – miconazole nitrate (LFX-MCZ) was analysed to be comprised in new transdermal therapeutic systems. Also, the compatibility of selected active substances and four polymeric excipients (hydroxypropyl methyl-cellulose - HPMC 15000, hydroxypropyl methylcellulose - HPMC E5, ethyl cellulose - EC 10, and hydroxyethyl cellulose – HEC) was studied.Methods: Thin layer chromatographic method (TLC) and four selected mobile phases were used. On the plate (in situ) were obtained the binary combinations (active substances and active substance-polymer).Results: A good compatibility of ADP-LFX was found using ammonia : methanol : acetonitrile : methylene chloride 2:4:1:4 mobile phase. Using chloroform : acetone : glacial acetic acid 34:4:3 on the chromatogram of ADP-MCZ, only ADP spots appeared but without changes in the shape of the spots and Rf values. Any modifications of LFX and MLX spots (from LFX-MLX mixture) had been observed using toluene : glacial acetic acid : methanol 11:1:0.5 mobile phase, although LFX spots have remained on the baseline. Only LFX spots were visible from LFX-MLX and LFX-MCZ mixtures (ammonia : methanol : acetonitrile : methylene chloride 2:4:1:4 mobile phase). Distinctive spots were observed for ADP, LFX and MLX with variable results from no chemical interactions to limited chemical interactions when the compatibility with polymers was verified.Conclusions: ADP-LFX and LFX-MLX mixtures were found to be compatible. ADP with HPMC polymers and LFX with HPMC E5 and HEC had presented excellent compatibility; for the other binary combinations, different analytical methods will be necessary.

The main objective of this review is to highlight the urgent development of new antiviral drugs against SARS-CoV-2 in the context of the coronavirus pandemic. Antiviral medication against SARS-CoV-2 comprises only remdesivir as an approved drug. Scientists are making considerable efforts to identify other effective antivirals. Investments into the de novo design of new drugs against the SARS-CoV-2 virus are few. Molnupiravir proved to be effective against the SARS-CoV-2 virus and is very close to approval. Pfizer’s two new compounds (PF-07321332, oral administration and PF-07304814, systemic administration) are in the early stages of development. Two types of methods are preferred to discover new antivirals in a short period. Repositioning of approved drugs for antiviral effect conducted to some clinical results for favipiravir, lopinavir/ritonavir, danoprevir/ritonavir, umifenovir, hydroxychloroquine, camostat and nafamostat. Virtual screening of known molecules’ libraries indicated several compounds that were tested or are being tested in clinical trials. In conclusion, only a few innovative antiviral molecules are in various stages of development. However, the repositioning of many known compounds is being studied, including using virtual screening. The pharmaceutical industry is adapting and reinventing itself so that humanity can face a new pandemic in the future.