**Variability of Plasma Methadone Concentration in Opiate Dependent Receiving Methadone: A Personalised Approach Towards Optimizing Dose**

Nasir Mohamad1,3, Nor Hidayah Abu Bakar2, Tan Soo Choon3, Sim Hann Liang3, NIM Nazar3, Ilya Irinaz Idrus3 and Rusli Ismail3 *1Department of Emergency Medicine, School of Medical Sciences, Health Campus, Universiti Sains Malaysia, Kubang Kerian, Kelantan, 2Department of Pathology, Hospital Raja Perempuan Zainab II, Kota Bharu, Kelantan,*  <sup>3</sup>*Pharmacogenetic Research Group, Institute for Research in Molecular Medicine (INFORMM), Health Campus, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia* 
