This study was carried out to formulate and evaluate controlled release (CR) matrix tablets of Acyclovir using combination of hydrophilic and hydrophobic polymers. Acyclovir is a guanine derivative and is its half-life is short hence administered five times a day using immediate release tablets. Six formulations (F1-F6) were developed using Ethocel and Carbopol in equal combinations at drug-polymer (D:P) ratio of 10:5, 10:6, 10:7, 10:8, 10:9 and 10:10. Solubility study was performed using six different solvents. The compatibility studies were carried out using FTIR and DSC. According to USP, Quality Control and dimensional tests (hardness, friability, disintegration and thickness) were executed. In-vitro drug release studies of Acyclovir was carried out in dissolution apparatus using using 0.1 N HCl medium at constant temperature of 37 ± 0.5 ºC. In order to analyze the drug release kinetics, five different mathematical models were applied to the release data. The results showed that there was no incompatibility between drug and polymers. Physical QC tests were found within limits of USP. The release was retarded upto 24 hrs and non-fickian in-vitro drug release mechanism was found. A formulation developed using blend of polymers, showed excellent retention and desired release profiles thus providing absolute control for 24 hrs.

Multiple drugs administration is a common practice in hospitals and clinics. This is the case when heavy pathologies are treated. In this context, frequently, antivirals and antibiotics are co-administrated either simultaneously or sequentially ignoring potential incompatibilities. In this study, we focused on an antiviral (Acyclovir) and an antibiotic (Ciprofloxacin) compatibility/incompatibility when they co-administrated with special interest on the effect of drugs ratio, pH and delay. By implementing robust HPLC method, we determined the main factors leading to potential modification of concentration of one of the two drugs in the mixture. The results showed that acyclovir is quantitatively recovered in all conditions related to pH, concentration and time (up to 24 hours). However, ciprofloxacin is strongly altered in acidic and basic conditions, the quantity of ciprofloxacin and time after mixing the two drugs. The most valuable piece of information is that the ratio of acyclovir/ciprofloxacin is crucial. The latter should be calculated and managed to provide at least two fold quantity of acyclovir versus ciprofloxacin in order to maintain the administrated doses and warrant efficient therapeutic effect.

Interpolyelectrolyte complexes Eudragit® EPO/L100 received in different pH were characterized by different degree of swelling in mimicking fasted stomach medium (0.1 M HCl) and saved their shape during 6 hours of the experiment. The microenvironmental changes in IPECs structure during swelling testing were inves-tigated using FT-IR spectroscopy, thermal and elemental analysis. Both samples of IPECs during swelling were transformed to a similar structure with approximately the same composition. IPEC samples showed bioadhesive properties that was not significantly different from the positive control (Carbopol) in the test with the mucin compacts. The release rate of metronidazole (class I BCS) from IPEC matrices increased with the increasing degree of swelling. IPEC 1 provided 49.62 ± 6.20% and IPEC 2 – 87.69 ± 5.15 % of metronidazole release after 6 hours in mimicking fasted stomach medium (0.1 M HCl). Total amount of released acyclovir (class III BCS) from IPEC 1 was 25.76 ± 5.67 % and from IPEC 2 was 21.48 ± 5.00 %. Release of both drugs was controlled by relaxation of polymeric chains in matrices according to the Peppas-Sahlin model. According to the received results, investigated interpolymer complexes are perspective for further evalua-tion as carriers for gastroretentive bioadhesive systems.

Combining antiviral drugs with different mechanisms of action can help prevent the development of resistance by attacking the infectious agent through multiple pathways. Additionally, by using faster and more economical screening methods, effective synergistic drug candidates can be rapidly identified, facilitating faster paths to clinical testing. In this work, a rapid method was standardized to identify possible synergisms from drug combinations. We analyzed the possible reduction of antiviral effective concentration of drugs already approved by the FDA, such as ivermectin  (IVM), ribavirin (RIBA) and acyclovir (ACV) against Zika virus (ZIKV), Chikungunya virus (CHIKV) and herpes virus type 2 (HHV-2). Essential oils (EOs) were also included in the study since they have been reported for more than a couple of decades to have broad-spectrum antiviral activity. We also continued studying the antiviral properties of one of our patented molecule with broad-spectrum antiviral activity, the ferruginol analogue 18-(phthalimid-2-yl)ferruginol (phthFGL). In general, the combination of IVM, phthFGL and Oregano EO showed the greatest synergism potential against CHIKV, ZIKV and HHV-2, obtaining a reduction in the EC99 value of up to ~8, and ~27, and ~12-fold for CHIKV, in example, respectively. The ternary combination RIBA, phthFGL, Oregano EO was slightly more efficient than the binary combination RIBA/phthFGL but much less efficient than IVM, phthFGL, Oregano EO which indicates that IVM could contribute more to the differentiations of cell targets (for example by inhibition of host heterodimeric importin IMP α/β1 complex) than ribavirin. PhthFGL showed a good pharmacokinetic profile.