The glabellar area is one of the danger zones as far as injecting fillers is concerned and must be done by an experienced physician, a board certified dermatologist or plastic surgeon with proper training and experience with injecting fillers.
The concern is compression or occlusion of blood vessels in the glabellar area causing necrosis (death of tissue) in the surrounding skin.
The only fillers that I recommend in the glabella are hyaluronic acid fillers such as Juvederm or Restylane. In the event of an occlusion of a blood vessels, hyaluronidase, an enzyme that dissolves hyaluronic acid can be injected to open up the blood flow. That cannot be done with Radiesse. Once Radiesse, an otherwise excellent filler for other facial areas, such as cheeks, temples and jowls, is injected into the skin, nothing but time can dissolve it. The body dissolves Radiesse in approximately one year, which is too long to wait if there is an adverse event.