<prompt> The basis of combining Ritonavir with LopinavirPharmaceutical compatabilityCYP3A4 inhibiton NY RitonavirLong elimination half life of RitonavirAbility to counteract side effects of Lopinavir  <response>: Refer Katzung 10e p810 Ritonavir is a microsomal enzyme inhibitor paicularly of CYP3A4 .it decreases the metabolism of other drugs and thus lower dose of Lopinavir can be used in treatment of HIV when combined with Ritonavir 