Takes 18 months at most.
Allison Don 14, has published as part of University of Minnesota Law School Scholarship Repository, 2014, "Lighten Up – Amending the Single Convention on Narcotic Drugs," Minnesota Journal of International Law, https://scholarship.law.umn.edu/cgi/viewcontent.cgi?article=1278&context=mjil, anita
Article 47 within the Single Convention provides instructions for amending the treaty, stating that “[a]ny [p]arty may propose an amendment to this Convention.”156 In order to make such a proposal, the amendment itself and the reasons behind the amendment must be transferred to the Secretary-General of the United Nations in writing who will then disseminate the proposed amendment to the other parties of the treaty and the Commission. At this point, the Commission has the power to decide if a conference should be held to discuss the proposal or if the parties should simply be asked if they are willing to accept.157 If there is no objection within 18 months, the amendment becomes fully adopted; if there is an objection, the Commission may then choose to hold a conference to review the proposal.158