Etoricoxib was obtained as gift sample from Cadila Healthcare Ltd. Ahmedabad and celecoxib (IS) was obtained as generous gifts from Cipla Pharmaceutical Pvt. Ltd. Mumbai. HPLC grade Acetonitrile was purchased from Merck Chemicals, Mumbai, Maharashtra, India. Andrographolide (AN) was purchased from Research Organic Pvt. Ltd, Chennai. A. paniculata Nees extract (APE) was procured from Natural Remedies Pvt. Ltd, Bangalore (Batch no. FAPEX/2013110012) (≥30% Andrographolide). High purity deionized water was obtained from Millipore, Milli-Q (Bedford, MA, USA) water purification system.