In medicine, combination therapy is a form of treatment that follows more than one therapy principle at the same time. In most cases, these are drug treatments that are aimed at more than just one active ingredient. This type of drug administration can encompass two different drugs or correspond to a combination preparation that has more than one active ingredient.

The opposite of such a form of treatment is called monotherapy and is limited to one active ingredient. Combination therapies can be divided into several sub-types. The best known are triple and quadruple therapy. While three drugs are used in triple therapy, quadruple therapy uses four active ingredients at the same time. For the first group, Helicobacter pylori eradication to eliminate the Helicobacter bacterium as completely as possible is one of the best-known examples.

In addition, the life-prolonging HIV therapy is sometimes a triple and sometimes even a quadruple therapy. The greatest advantage of any combination therapy is the simultaneous impact on various parameters of the disease. On the other hand, the biggest disadvantage compared to monotherapy lies in the usually high side effects of the treatment form.

Function, effect & goals

With a combination therapy, several factors of a disease can be positively influenced at the same time. Which drugs can be combined in the course of such a measure depends on the disease in question, but the interactions and side effects of the individual drugs are also important.

Combination therapy plays a particularly important role in current medicine in the treatment of HIV patients. The most effective form of treatment in the fight against the HIV virus is currently a highly active antiretroviral therapy that uses at least three different drugs. All three drugs contain antiretroviral, i.e. virus-blocking agents. Usually, two nucleoside reverse transcriptase inhibitors are used and combined together with a non-nucleoside reverse transcriptase inhibitor or protease inhibitors.

The effectiveness of the latter is often additionally increased via a booster. This combination can limit viral replication to the point where HIV can no longer be directly detected and patients’ lives can be extended through a lasting, if not always full, restoration of immune function. Many typical symptoms of HIV decrease in the course of therapy and the risk of the disease progressing is minimized.

Similar to this combination therapy, three different drugs are also used in Helicobacter pyori eradication. In the course of this measure, amoxicillin is usually combined with clarithromycin and proton pump inhibitors, but the combination of amoxicillin, metronidazole and proton pump inhibitors is also conceivable. A third route is the concomitant administration of metronidazole, clarithromycin and proton pump inhibitors. In addition to these combination therapies, combination therapies are often used in the case of epilepsy , blood pressure disorders or type II diabetes , for example.

However, combination therapies can also prove to be useful for diseases such as hepatitis C , ADHD , cardiac arrhythmias and complex tumors . As a rule, the principle applies: the more complex and diverse the disease, the more sensible it is to use a form of therapy with several active ingredients, since complex diseases in particular usually contain many different factors that cannot usually be adequately counteracted with a single active ingredient.

Risks, side effects & dangers

Any combination therapy should only be carried out with careful consideration of drug interactions. In addition, there are often significantly higher side effects for combination therapies than for monotherapies. Therefore, the doctor treating you must work with the patient to determine the benefit-risk ratio for the individual case in advance.

With triple therapy for HIV patients, for example, the benefits are usually significantly higher than the risks. Most patients tolerate the therapy method, which has been in existence since 1996, extremely well for many years. Nevertheless, side effects such as a feeling of fullness , vomiting or diarrhea can occur with this treatment route. A slight increase in liver values ​​can also occur, since some of the drugs have liver-toxic properties, which, however, only cause actual liver damage in extremely rare cases.

Kidney dysfunctions are also conceivable and neuropathies , sleep disorders and nightmares can occur in the course of treatment. Allergies and fat distribution disorders are among the most common side effects. Of course, the list of these side effects cannot be transferred to combination therapies for other diseases that involve completely different active ingredients and thus effects on the body.

The list is therefore only intended to illustrate the generally increased side effects associated with combination therapies. Especially when a combination therapy is used over a longer period of time, patients often develop resistance to one of the active ingredients used. For this reason, research is constantly being carried out into other active ingredients that can be combined with each other without risk and for every combination therapy approach.