<prompt> Marketing of these drugs is difficult and they are highly expensive to produce:Orphan drugsRare drugsOver the counter drugsEmergency drugs  <response>: Orphan Drugs are drugs or biological products for diagnosistreatment 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, OTCdrugs 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 