Long term (current) use of chemotherapeutic agent

• Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
• (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
• (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.

any follow-up examination (Z08-Z09)

long term (current) drug use for prophylactic purposes

• drug abuse and dependence (F11-F19)
• drug use complicating pregnancy, childbirth, and the puerperium (O99.32-)

any therapeutic drug level monitoring (Z51.81)

• long term (current) use of steroids (Z79.5-)
• long term (current) use of agents affecting estrogen receptors and estrogen levels (Z79.81-)