The following categories of substances are controlled by International Treaties due to their abuse potential.
Countries have annual quotas for each substance that comes under the categories of narcotic drugs and psychotropic substances. They are required mainly for medical and scientific purposes. To transport a controlled substance across a border, sanctions of competent authorities of both countries are required, and the quantity should be within the importing countries quota.
These are substance used as either precursors or catalysts in the synthesis of illicit drugs. National Dangerous Drugs Control Board, Sri Lanka (NDDCB - www.nddcb.gov.lk) is the competent authority for precursors in Sri Lanka and import authorizations should be obtained from them.
Most precursors are used for industrial purposes, but there are few medicines such as ephedrine, pseudoephedrine, ergometrine and potassium permanganate included among precursors.
Reference: INCB Website.