Nitazoxanide and azithromycin for the early treatment of COVID‐19: A multi‐spectroscopic, biochemical and computational drug–drug interaction study

• Published in: Journal of the Chinese Chemical Society (Taipei) Vol. 70; no. 7; pp. 1568 - 1579
• Main Authors: Ali, Syed Abid, Abid, Muhammad, Ahmed, Ayaz, Wadood, Abdul, Ahmed, Shakil
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley‐VCH Verlag GmbH & Co. KGaA 01-07-2023; Wiley Subscription Services, Inc
• Subjects: Aqueous solutions; azithromycin; Binding; Blood plasma; coronavirus; Dichroism; Drug interactions; Drugs; drug–drug interaction; Fourier transforms; Free energy; Infrared spectroscopy; Ions; Mathematical analysis; Molecular docking; nitazoxanide; Spectrum analysis; Stoichiometry; Toxicity; Zidovudine
• ISSN: 0009-4536; 2192-6549
• DOI: 10.1002/jccs.202350075

Herein, we present an experimental and theoretical drug–drug interaction study between nitazoxanide (NTZ) and azithromycin (AZT) in an aqueous solution. Interaction was studied by using UV/Vis, fluorescence, attenuated total reflectance‐fourier transform infrared (ATR‐FTIR), and circular dichroism (CD) spectroscopy, while molecular docking studies were performed to establish the interaction computationally. A bright yellow color was observed when the two drugs interacted, giving a hyperchromic band at 420 nm. The rate of absorbance was linearly increased by increasing drug concentrations and in a time‐dependent manner. Stability of the interaction complex (i.e., NTZ: AZT) was measured at variable temperatures (25–80°C), pH (5.0–10.0) and ionic strength (0.05–2.0 M NaCl), and not only proved stable but also retained antimicrobial potential with reduced cellular toxicity. Mole ratio and Job's method of continuous variations were used to establish the binding stoichiometry and found to be 2:1. The calculated binding constant (kb = 8,400 M−1) and Gibb's free energy (ΔG° = −22.4 KJ/mol) also suggested an energetically favorable interaction. FTIR spectra of NTZ: AZT complex in comparison with two drugs alone revealed significant interaction which was nicely complemented by molecular docking studies. Interaction was also successfully demonstrated in presence of carrier protein HSA and by spiking the two drugs in real samples of human plasma and urine.
Nitazoxanide and Azithromycin are widely used for the early treatment of COVID‐19. Drug–drug interaction between Nitazoxanide and Azithromycin is demonstrated. Multi‐spectroscopic, biochemical, and computational studies decipher the drug's interaction. Thermodynamic studies revealed that the interaction is energetically favorable. Drug–drug interaction is also validated by spiking the two drugs in biological samples. The study provided new protocol for drug's interaction, efficacy, and bioavailability in combination therapy.