In this chapter, several clinical pharmacological or regulatory science issues on carnitine are described. First, history of clinical application of pharmaceutical carnitine in the world is reviewed. Carnitine deficiency was reported in very rare inherited metabolic diseases, so carnitine was approved as a kind of orphan drug in most countries. It is very difficult to establish efficacy and safety evidence in rare diseases. The related academia made tremendous efforts, but pharmaceutical companies are reluctant to initiate drug development in these areas, and sectionalism in regulatory government hindered the approval or insurance coverage. Carnitine is a nutrient and there are many supplement products, so most physicians ignore or despise. I encountered all of these issues and struggled with them. This chapter is a kind of detailed Afterword, but it might be used as a reference for medical professionals who struggle for better treatment of patients but are blocked in their way, with same kinds of issues occurring in various countries in the world.