<prompt> True about tachyphylaxis is:Direct sympathomimetics involvedMechanism clearly understoodEphedrine tachyphylaxis reversed with dopamineIndirect sympathomimetics involved  <response>: Tachyphylaxis refers to rapid development of tolerance when doses of a drug repeated in quick succession result in marked reduction in response . This is usually seen with indirectly acting drugs , such as ephedrine , Tyramine , nicotine. From medical pharmacology padmaja 4th edition page no 70 