Dr Cressey has held a position at the Harvard School of Public Health within the Program for HIV Prevention and Treatment (PHPT) group based in Chiang Mai, Thailand since 2001. He has been actively involved in HIV clinical research studies, primarily focused on mother and child health. Dr Cressey has performed multiple clinical pharmacokinetic studies aimed at optimizing antiretroviral drug dosing for adults, adolescents, children, pregnant women and newborns. He is currently a member of the World Health Organization (WHO) - Pediatric Antiretroviral Working Group (PAWG).
He is also an active member of the NIAID-funded International Pediatric Maternal Adolescent AIDS Clinical Trials (IMPAACT) network and the Paediatric European Network for Treatment of AIDS (PENTA); where he acts as the study pharmacologist on several protocols.
Population pharmacokinetic models are particularly useful for analyzing newborns and children data due to blood sampling/volume limitations and he has published several population pharmacokinetic models using pooled data sets from different countries to guide infant dosing.
To support both investigator-initiated and network studies undertaken in Thailand, he has established a pharmacology laboratory at the Faculty of Associated Medical Sciences at Chiang Mai University. This laboratory contains state-of-the art equipment and is ISO 15189 accredited.
He is currently involved in the assessment of novel pediatric antiretroviral foundations in Africa and pharmacokinetics of Hepatitis-C virus antiviral treatment in Malaysia and Thailand.