If you are too sensitive to the damage, then a numbing agent is used to avoid any minor discomfort during the injection
Fosphenytoin was the preferred medication for a lot of the 20th century
Cecal samples Cecal weight was measured since the weight of this portion of the intestine appears to be highly influenced by the microbiome (e.g., certain antibiotic treatments dramatically increase cecal weight 27,28,29,30,31 but not the colon 27 )
Imagine how much longer that would be if you still had to ingest, break down, and absorb the B12 before the 12-48 hour period started
(2003) Replacement therapy for vitamin B12 deficiency: comparison between the sublingual and oral route
This falls into the range of codes related to musculoskeletal system services in the Current Procedural Terminology coding book