One of my prescriptions was out of stock at the pharmacy today. Good thing I have like 50 extras or I'd be screwed right now. How are you out of stock on a common medication? I don't get it.
Supply chain issues have been affecting medicines availability right across the board from common to your more obscure meds.
This is actually a global problem. In the UK, with year upon year worsening of the supply chain being observed, it's safe to say its reached unprecedented levels.
Many factors can affect a medicines availability. This can range from a batch failure picked up by QC and so leading to a product recall or technical issues developing during the manufacturing process. It's also not uncommon for situations to arise where demand greatly outstrips supply of which there can be many reasons.
Raw materials is another major contributor. In many cases these are brought in from overseas. Also worth considering that medicines themselves will be manufactured in other countries and then imported. Factors such as Covid, Ukrainian Russian War, The Middle East Crisis (affecting the Red Sea shipping routes) , economic instability and for Britain - Brexit have all had a significant impact on medicines supply.
Coupled to this, some manufacturers as well as wholesalers "gaming" the system so as to increase their profits.
Hopefully this provides some insight into how medicines can be in short supply.