BackgroundNonadherence with medication is a complex and multidimensional health care problem. The causes may be related to the patient, treatment, and/or health care provider. As a consequence, substantial numbers of patients do not benefit optimally from pharmacotherapy, resulting in increased morbidity and mortality as well as increased societal costs. Several interventions may contribute to improved adherence. However, most interventions have only a modest effect. Thus, despite the many efforts made, there has been little progress made as yet in tackling the problem of nonadherence.MethodsThis paper summarizes the definitions and taxonomy of adherence with medication, as well as types and causes of nonadherence. In addition, interventions aimed at improvement of adherence are discussed.ConclusionThere is not just one solution for the nonadherence problem that fits all patients. Most interventions to improve adherence are aimed at all patients regardless of whether they are adherent or not. Recently, a number of tailored interventions have been described in the literature. Modern techniques are useful. Electronic pill boxes combined with Short Message Service reminders are specifically designed to improve unintentional adherence and have resulted in an increase in refill adherence in diabetic patients with suboptimal adherence. Tailored Internet interventions are a possibility for influencing patient drug-taking behavior and show promising results. Tailored counseling interventions targeted at the underlying causes of nonadherence seem an attractive method for supporting patients with their use of drugs. However, despite the plausible theoretical framework, data on long-term health effects of the various interventions are not available. To improve adherence effectively, there is a need for a tailored approach based on the type and cause of nonadherence and the specific needs of the patient.

Side effects of antidepressants are usually underreported in clinical trials and large scale naturalistic studies are restricted to six months of use. We examined the prevalence and nature of patient-perceived side effects and their determinants during long-term antidepressant use in a naturalistic setting. Subjects, aged 19 to 67 years, in the Netherlands Study of Depression and Anxiety were recruited from primary care and specialized mental health care covered 927 cases of single antidepressant use. In 64% of cases, on average, 2.9 side effects were reported. The number of side effects was higher when subjects had higher depression severity (OR=1.28; p=0.002), three or more psychiatric diagnoses (OR=1.97; p=0.02), higher dose (OR=1.44; p=0.006) and was lower when subjects were older (OR=0.83; p=0.02) and had longer duration of use (OR=0.94; p=0.04). Tricyclic antidepressants were associated with more side effects (OR=2.52; p=0.003) and, particularly, more anticholinergic effects, like dry mouth and constipation, as compared to selective serotonin reuptake inhibitors. Venlafaxine showed more profuse sweating (OR=1.79; p=0.007), whereas mirtazapine showed more weight gain and less sexual dysfunction (OR=0.36; p=0.03), as compared to selective serotonin reuptake inhibitors. Weight gain was associated with female gender (OR=1.76; p=0.004) and duration of use (OR=1.06; p=0.03). We show that antidepressant side effect, known from short-term studies, persist during long-term use and are associated with depression severity and antidepressant dose. A novel finding was that venlafaxine is associated with more profuse sweating and that weight gain appeared more specific in female users. Clinicians should be aware that, during long-term antidepressant use, side effects are common and persistent.

PDIs are common in patients treated for an (haemato-) oncological disease. Screening for potential interactions should take place routinely before administering chemotherapy.

Non-adherence to antihypertensive medication is the most important cause of uncontrolled blood pressure and is influenced by multiple interrelating factors. Understanding the complexity of medication non-adherence and its associated factors is important to determine intervention strategies. Therefore, a systematic review was performed aimed to identify factors associated with antihypertensive medication non-adherence. Different databases were searched for observational studies reporting on factors associated with non-adherence to antihypertensive medication. Titles, abstracts and full texts were reviewed by three researchers. Subsequently, the methodological quality of each study was assessed. Factors that were extracted from the included studies were categorised as factors with consistent or inconsistent evidence to put their potential importance into perspective. Forty-four studies were included. Higher co-payment, side effects and a poor patient-provider relationship were identified as factors with consistent evidence since consistent significant relationships were found for these factors whenever studied. The relationships between non-adherence and multiple other factors were inconsistent among the reviewed studies. However, some of these factors deserve some consideration. Since multiple potentially relevant factors were identified, patient-tailored interventions focussing on identifying and addressing patients' specific barriers to adherence are needed. Further research should clarify the influence of inconsistent factors on adherence and their potential to be addressed in interventions.