You can carry medication, such as buprenorphine and methadone, when entering the Netherlands. If you live in a country in the Schengen zone, you need a “Schengen certificate”. Under the Convention implementing the Schengen Agreement, private persons wishing to travel within the Schengen Area and carry narcotic drugs and/or psychotropic substances must have a certificate proving that these are necessary for their medical treatment. The Schengen member states are Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden and Switzerland. Application procedures for the certificate in the Schengen countries differ.
If you are from outside the Schengen zone, you will need a medical certificate drawn up in English and which is valid for one year. Ask the doctor who prescribed your medicines to draw up and sign a medical certificate. Legalize the certificate according to the regulations in your own country. When you travel to the Netherlands, keep your medicines in their original packaging. This makes it clear to customs that the drugs are medicines, not illegal drugs. It is preferable to have the drugs in your hand luggage (in case your baggage gets lost).