system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Pupil fails to dilate by giving cocaine in –
assistant
The correct answer is  In periphery cocaine blocks the uptake of Adrenaline and Noradrenaline in Adrenergic nerve ending resulting in higher concentration of sympathetic neurotransmitters (Sympathomimetic effect) :
The peripheral sympathomimetic action of cocaine produces following effect :


Mydriasis
Rise in B.P.
Local vasoconstriction
Tachycardia


Therefore if the peripheral sympathetic system is paralysed it will lead to reverse of the above mentioned actions.