The COVID-19 pandemic has resulted in more than 30.35 million infections and
9, 50, 625 deaths in 212 countries over the last few months. Different drug
intervention acting at multiple stages of pathogenesis of COVID-19 can
substantially reduce the infection induced mortality. The current within-host
mathematical modeling studies deals with the optimal drug regimen and the
efficacy of combined therapy in treatment of COVID-19. The drugs/interventions
considered include Arbidol, Remdesivir, Inteferon (INF) and
Lopinavir/Ritonavir. It is concluded that these drug interventions when
administered individually or in combination reduce the infected cells and viral
load. Four scenarios involving administration of single drug intervention, two
drug interventions, three drug interventions and all the four have been
discussed. In all these scenarios the optimal drug regimen is proposed based on
two methods. In the first method these medical interventions are modeled as
control interventions and a corresponding objective function and optimal
control problem is formulated. In this setting the optimal drug regimen is
proposed. Later using the the comparative effectiveness method the optimal drug
regimen is proposed based on basic reproduction number and viral load. The
average infected cell count and viral load decreased the most when all the four
interventions were applied together. On the other hand the average susceptible
cell count decreased the best when Arbidol alone was administered. The basic
reproduction number and viral count decreased the best when all the four
interventions were applied together reinstating the fact obtained earlier in
the optimal control setting. These findings may help physicians with decision
making in treatment of life-threatening COVID-19 pneumonia.Comment: 16 pages, 13 figure