What is Celeste experiencing when she develops pain and an intense craving for heroin?

Celeste is experiencing withdrawal when she develops pain and an intense craving for heroin. Withdrawal refers to the array of physical and psychological symptoms that occur when an individual who is dependent on a substance stops using it or significantly reduces its intake. These symptoms can include not only cravings but also physical discomfort, pain, anxiety, and a variety of other effects that are uncomfortable and can drive a person back to substance use.

In the context of substance use, craving is a hallmark of withdrawal, as the body and brain react to the absence of the drug. With heroin, specifically, withdrawal can be particularly intense and may manifest as physical pain, agitation, and other distressing symptoms, which characterize the body’s response to not having the substance it has adapted to.

The other options are not indicative of the symptoms Celeste is experiencing. Tolerance relates to the need for increasing amounts of a substance to achieve the same effect, but doesn't directly involve withdrawal symptoms. Insomnia refers to difficulty sleeping, which may occur for various reasons, but is not directly linked to the experience of craving and pain following cessation of heroin use. Narcolepsy is a neurological condition characterized by excessive daytime sleepiness and sudden sleep attacks, unrelated to substance withdrawal.