Chemotherapy Drug Doses and Schedules: How They Are Determined
Some drugs, especially those available to people without a prescription, have a fairly wide therapeutic index. This means that wide ranges of doses can be used effectively and safely. For example, the label on a bottle of aspirin may suggest taking two tablets for a mild headache. But one tablet (half the dose) is likely to be enough to help many people.
Most chemotherapy drugs, on the other hand, are strong medicines that have a fairly narrow range of safe and effective doses. Taking too little of a drug will not effectively treat the cancer. Taking too much may cause life-threatening side effects. For this reason, doctors must calculate chemotherapy doses very precisely.
Doses are calculated considering a variety of factors including body weight, body surface area and levels of sensitivity to the chemo drugs. The drugs used usually determine the schedule (cycles) in which chemo is given. Circumstances that arise during a chemo treatment may require changes to the schedule.
Chemotherapy drugs are given over time. The schedule for when doses are given and for how long is usually determined by which drugs are used. (A chemo drug schedule is known as a "cycle.")
- How often chemotherapy is given varies. You may take chemo once a day, once a week, or even once a month, depending on the type of cancer you have and the chemotherapy you are taking.
- How long you take chemotherapy depends on the type of cancer, how you respond to the drugs, and what length of time led to the best treatment results in research studies. (Research studies are known as "Clinical trials.")
Circumstances that arise during a chemo treatment may require changes to the schedule.
For more information, see the other sections of this article.