The __________, the degree to which a substance is poisonous or can cause injury, of a drug or other substance depends on many factors: the dose (how much of it is taken in or absorbed), the duration (the frequency and length of the exposure), the nature of the exposure (whether it was ingested, inhaled, or absorbed through the skin), and other individual factors, such as whether the drug or toxin interacts with other substances in the body such as alcohol or prescription drugs.