Marketing of these drugs is difficult and they are highly expensive to produce:

Orphan Drugs are drugs or biological products for diagnosis/treatment/ prevention of a rare disease or condition. cost of developing and marketing is high eg: sodium nitrite, fomepizole, liposomal amphotericin B, rifabutin, succimer, somatropin, digoxin immune Fab (digoxin antibody), liothyronine (T3), etc Over the counter, (OTC)drugs or Nonprescription drugs can be sold even by grocery stores-they are available and can be dispensed without prescription Ref ;KD Tripathi pharmacology 7 th edition (page no; 5)