Systematic Review of the Apomorphine Challenge Test in the Assessment of Dopaminergic Activity in Schizophrenia.

So far, neuroendocrine studies conducted in schizophrenic patients have yielded conflicting results. Many of these discrepancies may be explained by the diversity of factors that influence the hormonal levels (at baseline and in response to pharmacological stimuli), the heterogeneity of the populations studied, the absence of standardization of test challenges and the confounding and long-lasting effects of previous treatments. Numerous studies have used apomorphine (APO) in the evaluation of dopaminergic (DA) function in schizophrenic patients. APO, a direct acting DA receptor agonist, decreases prolactin (PRL) and stimulates growth hormone (GH), adrenocorticotropic hormone (ACTH) and cortisol secretion. Therefore, the magnitude of hormonal responses to APO is an indirect assessment of the functionality of DA receptors at the hypothalamic-pituitary level. This review provides an update on the applications of the APO test in schizophrenia in clinical, pathophysiological and therapeutic fields.

Differences in multihormonal responses to the dopamine agonist apomorphine between unipolar and bipolar depressed patients.

BACKGROUND: A large number of studies suggest that dopaminergic function may be impaired in depressed patients, particularly in bipolar patients. The dopamine D2/D1 agonist apomorphine (APO) can be useful in the evaluation of dopaminergic function. However, most studies show conflicting results in APO test responses when evaluating unipolar and bipolar depressed patients. Thus, the objective of this study was to apply the APO test to assess whether hypothalamic-pituitary dopaminergic function is altered in unipolar and bipolar depression. METHODS: We evaluated multihormonal responses to APO test (0.75 mg subcutaneous) in 134 drug-free DSM-IV major depressed inpatients (54 with bipolar depression [BD] and 80 with unipolar depression [UD]), compared with 36 healthy controls (HCs). We also examined the cortisol response to the dexamethasone suppression test (DST, 1 mg orally) in all subjects. RESULTS: No significant differences in prolactin (PRL), cortisol, adrenocorticotropin (ACTH) or growth hormone (GH) baseline values were found across the three groups. ACTH/cortisol and GH responses to APO were also comparable. BD patients showed lower PRL suppression to APO than did UD patients and HCs (both p < 0.00001). Although responses to DST were comparable between UD and BD patients, the former exhibited higher post-DST cortisol levels than did HCs (p < 0.05). CONCLUSIONS: Our results suggest that BD patients, unlike UD patients, have altered post-synaptic D2 receptor sensitivity at the pituitary level. This alteration does not seem secondary to hypercortisolemia. These findings, if confirmed by other studies with larger samples, may support the use of dopamine agents in BD patients treatment.

Clinical insights into use of apomorphine in Parkinson's disease: tools for clinicians.

Apomorphine was introduced before the era of levodopa as a treatment for idiopathic Parkinson's disease (iPD). A number of practical obstacles were to be solved before a wider use of the drug was possible. Today, however, the drug is probably still underutilized. Apomorphine is a strong nonergoline D1 and D2 receptor agonist with a dopaminergic effect comparable with levodopa. In this review motor and non-motor indications for intermittent injections and subcutaneous apomorphine infusions are listed. The reduction of 'off' periods is more than 50% on infusion therapy and if monotherapy is achieved a significant reduction of pre-existing levodopainduced dyskinesias is seen. The aim of this review is to give practical insight into apomorphine treatment, highlighting side effects, and complications and device-related problems are discussed with advice on how to prevent or handle these, should they occur. A number of practical points including the apomorphine test, requirements of the clinical setting, how to increase adherence and troubleshooting are added.