What does 'dependence' refer to in pharmacology?

In pharmacology, 'dependence' primarily refers to a state where an individual experiences withdrawal symptoms in the absence of a drug. This phenomenon occurs because the body has adapted to the presence of the drug, leading to physiological changes that require the substance for normal functioning. When the drug is discontinued, these adaptations can cause various physical and psychological withdrawal symptoms, which can vary depending on the substance involved.

The other options, while related to drug use and therapeutic interventions, do not accurately capture the concept of dependence. A desire to increase dosage reflects tolerance, which is different from dependence. The need to combine multiple drugs pertains to polypharmacy or combination therapy used for enhanced treatment effects, but does not indicate dependence. An allergic reaction to medication involves the immune system and is unrelated to the dependence on a drug. Thus, 'dependence' is clearly defined by the occurrence of withdrawal symptoms when ceasing drug use.