First, all prescription meds MUST BE prescribed by a licensed doctor and in a labeled container. (I've never been asked to show the actual prescription from the doctor.)
medicines OTC in some countries are cheaper, but could land you in serious trouble when you travel to another, or they simply might confiscate it. For example, Azithromycin is readily available OTC in Asia
...if you entered US with a Z-Pac without a prescription it would be confiscated and possibly fined.
A prescription from a licensed doctor is valid anywhere in the world. (I personally have never encountered any customs agent who questioned the validity a properly labeled bottle of prescription meds, and have never had a prescription med confiscated. This applies to both traveling by sea or air travel.)
The shelf-life on many meds is longer than indicated, and as long as not exposed to extremely high heat many tablets will last abt. 3 years in effectiveness (according to my doc).
As GoneDiving stated, make an itemized list of every single medication (prescription and non-prescription) on your boat along with quantity and the location
and present this document along with your ship's papers to the customs official. For prescription meds log all usage underway. If the prescription container indicates 20 tablets and there are only 10 you should have a record
of when / why used. This is especially important if you take certain medications (opioids) in port.
In Asia/SE Asia
they take opioid smuggling very seriously. As long as they are declared and accounted for I personally have not had my prescription confiscated. In Indonesia
I had to ensure that prescription was in a locked container; they counted the number on entry and exit. In Japan
the customs agent did not bat an eyebrow.
WRT to all meds being "locked up" in a medicine kit....no...I have specific prescription meds in my rapid ditch kit, others in my med kit, and my daily med on a cabinet in my cabin
. Again the key is that they are all listed on a form. Customs will sometimes inspect...mostly not.
If you're having difficulty with a doc prescribing you meds...switch doctors. Explain that you are going cruising and provide a list of specific meds and why you desire to have them aboard. A discussion indicating that you know when and how to administer those meds helps...go in prepared. Also Ocean Medix
provides prescription med kits w/prescription for common meds and IV packs.
In the US, some insurance
companies will deny prescriptions for more than 1 month supply. You can ask the pharmacist to request a "vacation waiver" from the ins. company if the amount is greater than 1 month supply. Your ins. co. may vary in it's policy...best to check.
Finally, you should be trained and knowledgeable on the various prescription meds and first aid that you have onboard. (I carry copies of my training
records for adv. first aid, CPR/AED (which I carry onboard), suturing, and peripheral IV insertion). Most opioids are useful for immediate intense pain relief...they are usually not good for long term use. Lomotil is good for persistent diarrhea (more than 1 day) to prevent dehydration...but could really block you up. Different antibiotics are used to treat different types of infections...learn which targets things like UTIs vs. staph infections and be aware that many antibiotics may also predispose you to sunburn.
Also, if you have crew...they must inform you of any drug allergies and any prescription meds they bring onboard.
Declaring things upfront when clearing into a country usually don't get you into trouble...if that country doesn't permit
something they usually just confiscate it. When you "forget" something or intentionally try to hide it...the outcome is usually not in your favor.
This has been my experience traveling by boat
through the Pacific & SE Asia. (Canadian customs was always more concerned with booze than with any meds onboard.) YMMV.