Talaromycosis continues to be a common opportunistic fungal infection among people living with HIV/AIDS (PLWHA) in Southeast Asia and remains a leading cause of death among this population. Itraconazole (ITZ) is an important component of talaromycosis treatment. In Thailand, the capsule formulation of ITZ is primarily used to treat talaromycosis but it is known to have lower bioavailability than the more expensive solution formulation. Limited data on the drug exposure of ITZ with the capsule formulation are available in adults PLWHA in Thailand. Moreover, the effect of efavirenz (EFV), which has been recommended as the first line antiretroviral therapy in Thailand, to ITZ level is not well understood. Thus, our aim is to assess ITZ pharmacokinetics with and without EFV in adult PLWHA receiving talaromycosis treatment with the capsule formulation. An understanding of the relationship between ITZ drug exposure and its active metabolite (hydroxyl-itraconazole) and treatment response is also planned to help optimize therapy.

Inclusion Criteria:

1. 18 years or older
2. Available documentation of HIV infection
3. ITZ capsule therapy is indicated for talaromycosis infection with the anticipation to start on EFV-based ART
4. Willing to consent and compliance to the study protocol

Exclusion Criteria:

1. History of ITZ allergy
2. Pregnancy or lactation
3. Use concurrent medication that could interfere with ITZ level
4. Creatinine clearance less than 30 mL/min
5. Alanine aminotransferase (ALT) or Aspartate aminotransferase (AST) value is more than 5 times of upper normal limit and total bilirubin is more than 3 times above upper normal limit
6. Hemoglobin less than 7 mg/dL
7. History of ITZ exposure within 35 days (only applicable to intense PK group)

HIV-infected participant who has an evidence of T. marneffei invasive infection will be enrolled to the study.