Mecobalamin tablets, a vitamin B12 formulation, are often given to patients with postoperative neurosensory disturbance of the lip after orthognathic surgery, especially those who underwent sagittal split ramus osteotomy. Intermaxillary fixation or elastic traction is required in these patients until the jaw bone fragments are stabilized. Due to restricted mouth opening, these patients have difficulty taking medication in the form of tablets. The simple suspension method is one means by which drugs can be delivered to such patients. In this study, we developed a new delivery method for a simple suspension of mecobalamin, which is light-unstable, by light shielding with mouthwash cups used in dental practice. Under daylight conditions, suspensions of mecobalamin tablets were prepared by the simple suspension method in three groups： unshielded preparation (unshielded group) , covered with a paper cup (paper cup group) , and covered with a stainless steel cup (stainless steel cup group) . The remaining amounts of mecobalamin were measured over time in these groups. The amount of mecobalamin remaining was 102.7％ at 5 min, 69.5％ at 10 min, 38.2％ at 15 min, and 7.7％ at 30 min in the unshielded group； 101.1％ at 5 min, 92.5％ at 10 min, 82.5％ at 15 min, and 59.8％ at 30 min in the paper cup group；and 100 ％ after 30 min in the stainless steel cup group. This study revealed that light-induced decomposition of mecobalamin suspensions can be prevented for 30 min by covering them with a stainless steel cup that can completely block light. Covering with a stainless steel cup is a simple light-shielding method that can be used when preparing the suspension at the time of administration. A medical care team with healthcare professionals such as oral surgeons, pharmacists, and nurses should provide effective methods of drug delivery to patients following orthognathic surgery, as they have difficulty taking drugs orally. Also, it is necessary to verify the efficacy of treatments provided by the medical care team for postoperative adverse events such as neurosensory disturbance.
