l carnitine and choline Red Meat Heart Disease: The Hidden Role of microbial L-Carnitine & Carnitine, Choline, Cancer, & Cholesterol:

Farsi F, Ebrahimi-Daryani N, Golab F, Akbari A, Janani L, Karimi MY, et al

While it effectively bypasses digestion, it introduces higher costs and safety risks compared to oral or topical alternatives

Frosst, P., Blom, H.J., Milos, R., Goyette, P., Sheppard, C.A., Matthews, R.G., Boers, G.J.H., den Heijer, M., Kluijtmans, L.A.J., van den Heuve, L.P., Rozen, R

For example, in the case of major depression, the symptoms of anhedonia and behavioral despair have been extensively used in animal studies and possess a degree of face validity for the clinical disorder, whereas the DSM-IV symptoms of guilt and suicidality are virtually impossible to evaluate in an animal (Nestler & Hyman, 2010)