Therapeutic Effects, Side Effects, and Adverse Effects of Neuropsychiatric Drugs in the Context of Treating Cancer-Related Anorexia With Olanzapine and Mirtazapine

Drugs have actions that may be classified as therapeutic effects and side effects; side effects are actions that do not contribute to therapeutic benefit. Some side effects are neutral; others, experienced as undesirable or unpleasant, are recorded as adverse effects. Some drug actions are therapeutic for some disorders and adverse for others; or therapeutic during acute illness and adverse during maintenance treatment. As an example, anticholinergic action may be adverse when a tricyclic antidepressant is used to treat depression but therapeutic when the drug is used to treat irritable bowel syndrome with diarrhea. In clinical practice, side or adverse effects of a drug may be leveraged to manage troublesome symptoms. As an example, the sedative effect of a low dose of trazodone may be useful for some patients with insomnia. With this background, studies have examined whether the increase in appetite and weight associated with olanzapine and mirtazapine may be effective against anorexia and cachexia associated with cancer and cancer chemotherapy. The subject is important because cachexia may be present in 30%-50% of patients with cancer (with higher prevalence in patients with more advanced cancer) and because the presence of cachexia is associated with a higher risk of disease progression and mortality. Many randomized controlled trials (RCTs) have examined pharmacologic interventions such as progestins, corticosteroids, anamorelin, and medical cannabis for cancer related cachexia; most results have been disappointing. A recent RCT found that olanzapine (2.5 mg/d for 12 weeks) improved appetite, weight, other nutritional parameters, and quality of life in patients with locally advanced or metastatic cancer treated with chemotherapy. Another RCT, however, found that mirtazapine (30 mg/d for 8 weeks) brought no nutritional or anthropometric gain in patients with cancer and anorexia. It is concluded that olanzapine but not mirtazapine merits further investigation in patients with cancer who have anorexia and cachexia.