Combination therapy or polytherapy is the use of more than one medication or other therapy (vs. monotherapy, which is any therapy taken alone). Typically, these terms refer to using multiple therapies to treat a single disease, and often all the therapies are pharmaceutical (although it can also involve non-medical therapy, such as the combination of medications and talk therapy to treat depression). 'Pharmaceutical' combination therapy may be achieved by prescribing/administering separate drugs, or, where available, dosage forms that contain more than one active ingredient (such as fixed-dose combinations).
Polypharmacy is a related term, referring to the use of multiple medications (without regard to whether they're for the same or separate conditions/diseases). Sometimes "polymedicine" is used to refer to pharmaceutical combination therapy. Unfortunately, most of these kinds of terms lack a universally consistent definition, so caution and clarification are often advisable.
 Uses for combination therapy
Conditions treated with combination therapy include tuberculosis, leprosy, cancer, malaria, and HIV/AIDS. One major benefit of combination therapies is that they reduce development of drug resistance, since a pathogen or tumor is less likely to have resistance to multiple drugs simultaneously. Artemisinin-based monotherapies for malaria are explicitly discouraged to avoid the problem of developing resistance to the newer treatment.
Combination therapy may seem costlier than monotherapy in the short term, but when used appropriately, it causes significant savings: lower treatment failure rate, lower case-fatality ratios, slower development of resistance and consequently, less money needed for the development of new drugs.
 Contrast to monotherapy
Monotherapy can be applied to any therapeutic approach, but it is most commonly used to describe the use of a single medication. Normally, monotherapy is selected because a single medication is adequate to treat the medical condition. However, monotherapies may also be used because of unwanted side effects or dangerous drug interactions.
 See also
- Polypill, a medication which contains a combination of multiple active ingredients
- "Glossary". Retrieved 2008-04-02. "Monotherapy: The treatment of epilepsy with a single medication rather than a combination. Monotherapy has advantages over combining medications in many patients, including absence of drug-drug interactions, fewer side effects, simpler dosing, and lower cost. However, not all patients can be controlled with monotherapy."