Arrange the following drugs according to increasing volume of distribution. 1. Haloperidol 2. Gentamicin 3. Heparin 4. Chloroquine

* Chloroquine has highest volume of distribution. It is concentrated in liver and retina. * Heparin is high molecular weight compound and thus not able to cross most membranes. It has low Vd. * Gentamicin again cannot cross many membranes because of polar nature and thus has low Vd. * Haloperidol is a drug working in CNS. So, it must be able to cross other membranes also resulting in high Vd. Thus the sequence is Chloroquine > Haloperidol > Gentamicin > Heparin