You can buy and IV/IM solution of Methocarbamol from a pharmacy in Canada. It's an "Ethical" product which means there is no federal law against selling/purchasing it but it generally is bought with a doctors script.
B12 for IM/SC use is an "Ethical" product and I buy it all the time. Same with many vitamins in injectable form. Even Promethazine and Benadryl are "Ethical" drugs....Quinidine, and Ephedrine are "Ethical".
The problem is, a pharmacist may argue with you or refuse to sell it. I've always told them to look on the health Canada websites DRUG PRODUCT DATABASE and check the glossary for the definition of Ethical drugs! Then look the drug up and see, that Health Canada considers _______ drug ETHICAL. Therefore there if they can sell B12 to me they can sell Methocarbamol or Promethazine. etc. If they argue. Tell them to go f themselves, leave, and phone other pharmacies.
But it sounds like to me you need to do some serious reading and educate yourself before you start IV'ing drugs like those I just mentioned. Including vitamins.
Be safe, please. I am not endorsing you to do drugs. Simply educating BL'ers in Canada of the law.