I'm sorry you had to get on the "Medicare merry-go-round" but your pharmacist has probably been flying under the radar on this issue.
Per Medicare regs, substances used in a nebulizer are covered by Part B IF the pharmacy also provided the nebulizer under a prescription while you were on Medicare, or IF the doctor writes a letter of medical necessity. I just looked for the actual document, and since reorganizing my computer I am sorry to say I cannot find it.
KEEP a copy of the letter the doctor provides in case your Walgreens closes (like many are doing) - mine did not make the transfer from the old pharmacy to the new one.

As for Fasenra and any other name brand injectable - it depends! But understandably, nobody wants to give you a $4000/month drug if a $400 will work. Our family has learned over time that these biologics are not without their own risks and side effects and some may not show up for many months. And as the newer meds are in use for a longer time, and by people who may have other health issues that were not covered in the drug approval trials, new side effects become known.

Here is the approval process in a nutshell:
- First, for nearly any expensive name brand injectable, there are things you must already have tried and failed before Medicare will cover them. These may be known as "step therapy." For example, you may to try Symbicort or a similar inhaler if you have not already done so.

- Next look at both Part B and Part D of your plan to see if/where Fasenra is covered. If possible, have the doctor's office secure the guidelines for prescribing from the insurer. Make sure the doctor has documented the reason for prescribing. If you inject it at home with an auto-injector it may be Part D. If it is done in the doctor's office or an infusion center, it is probably Part B, even if after a few doses they allow you to do it yourself.

- Third, you will get a coverage letter if it is approved, typically valid for 12-15 months. KEEP IT! If you change pharmacies, doctors, or your plan changes, you will need it again. If you change plans, like I did in January, you go back to square one and get to go through Medicare approval %^&* all over again.

- Fourth, you have well-defined appeal rights - use them! A lot of Pharmacy Benefit Managers (PMB's) are well known for saying "No" the first time and hoping you will go away. Every appeal I have ever filed has ultimately been allowed.

What I say is be flexible, be prepared, be organized, be patient and good luck. And keep in mind that the insurance and Medicare reps you will be dealing with are every bit as unhappy about this amusement park/fun house as we are.