I'm going to include a bunch of information below that I found while researching the Canadian Gov't websites. I think the key takeaway is that if this is a prescription-only medication, you may need to provide documentation that it was prescribed to you and indicate that it is for your own personal use. Plus you can't bring too much of it back (1 course and < 90 day supply).
To be honest I'd be surprised if a customs officer would be concerned since Redotex is a weight loss drug, not a commonly abused medication (such as an opioid or benzodiazepene). The page (Travelling with medication) from Government of Canada states:
Bringing prescription medication back to Canada
To avoid interrupting a course of treatment, Health Canada may permit you to return from abroad with a single course of treatment or a 90-day supply, whichever is less based on the directions for use, of a prescription drug. The drug must be for your use or for the use of a person who is travelling with you and for whom you are responsible. The drug must be in hospital or pharmacy-dispensed packaging, the original retail packaging, or have the original label attached to it clearly indicating what the health product is and what it contains.
Bringing over-the-counter medication back to Canada
You are permitted to import a single course of treatment or a 90-day supply, whichever is less based on the directions for use, of an over-the-counter drug. The drug must be for your use or for the use of a person who is travelling with you and for whom you are responsible. The drug must be shipped or carried in hospital or pharmacy-dispensed packaging, the original retail packaging, or have the original label attached to it clearly indicating what the health product is and what it contains...
Another page from Health Canada titled Guidance Document on the Import Requirements for Health Products under the Food and Drugs Act and its Regulations (GUI-0084) says: (under Figure 2. Personal Use Importation Requirements for Human Drugs)
Prescription Drugs (Schedule F) / Canadian Resident:
Importations of prescription drugs by Canadian residents are not permitted by mail or courier.
So as not to interrupt a course of treatment, Health Canada may use enforcement discretion to permit a Canadians returning from abroad to bring with them on their person a single course of treatment or a 90-day supply based on the directions for use, whichever is less, of a prescription drug.
The drug must be for the individual's own personal use or the use of a person for whom they are responsible and with whom they are travelling.
The drug must be in one of the following:
- Hospital or pharmacy dispensed packaging;
- Original retail packaging; or
- have the original label affixed to it which clearly indicates what the health product is and what it contains.
The following applies to Over the Counter Drugs (OTC), Schedule D drugs (drugs derived from Human, Animal or microbial sources, such as insulin and blood based products), or Natural Health Products (NHP)
Individuals are permitted to import a single course of treatment or a 90-day supply based on the directions for use, whichever is less, of an Over the Counter Drug.
The drug must be for the individual's own personal use or for the use of a person for whom they are responsible and with whom they are travelling.
The drug must be shipped/carried in one of the following:
- Hospital or pharmacy dispensed packaging;
- Original retail packaging; or
- have the original label affixed to it which clearly indicates what the health product is and what it contains.
I hope that all of this helps. Good luck with everything and please let me know how it goes! It could help someone else in your situation in the future.