 P1106 is Phase IV prospective pharmacokinetic PK study of low birth weight infants who are receiving or will be receiving as part of clinical care nevirapine NVP prophylaxis, tuberculosis TB prophylaxis or treatment andor combination antiretroviral ARV treatment containing lopinavirritonavir LPVr. The study is designed to describe the pharmacokinetics and safety of NVP, INH, RIF, and LPVr in these infants receiving the drugs as part of clinical care. 