Medicine is a pill, potion or other preparation for the treatment and prevention of disease or injury.
According to both the Shoninki and Giyoshu manuals, medicine was essential for a shinobi. If a shinobi gets sick in the field, he will not be able to accomplish his task. The two manuals recommend shinobi to carry field medicine at all times. The medicine mentioned is called kusuri. Kusuri means worm killer, this is because at the time people thought that stomachaches or food poisoning were caused by worms.
The Akutagawa Kaden claims shinobi needed to have at least a basic knowledge of medicinal plants and travel medicines. Recipes to cure sunstroke, vomiting, headaches, and to treat wounds are all required alongside other medical treatments and first aid that is needed while out performing a mission. There was a requirement for medical aid to prevent exhaustion under the extreme conditions shinobi worked under.
The Giyoshu military manual includes a recipe for a medicine which was meant to protect a person's hands and legs from frostbite made from peeled and chopped ginger and sake rice wine. The ginger and sake would be mixed in low heat and applied to the hands and legs. Alternatively, sake could be used alone, applied to the hands, legs, and face.
A cure all antidote is also mentioned in the Giyoshi manual made from pondweed seaweed charred on a gray heron's head. To stop bleeding bits of a charred wren would be placed on one's tongue or gohasso powder, made from a charred mamushi snake, would be sprinkled on the bleeding wound. On the other hand, pine ash and aucuba leaf could also be used to stop bleeding if placed on a wound. The manual recommends avoiding uncommonly used medicines.