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Multiple sclerosis (MS) individuals who use complementary and alternative medicine (CAM) generally do so because they experience improvement in their quality of life, and in various MS symptoms such as fatigue, spasticity, or pain. The different CAM therapies used commonly by individuals with MS are: mind-body therapies, dietary changes and supplement use that include low fat diet, essential fatty acids and anti-oxidants, ginseng, acupuncture, low-dose naltrexone and cannabis. Despite the widespread use of CAM therapies among MS patients, most of these therapies have not been evaluated in well-designed, randomized, controlled clinical trials, the lack of which is the main reason why most neurologists do not incorporate CAM therapies into their management of MS patients. Clearly there are certain therapies, such as anti-oxidants and essential fatty acids, which have a scientific rationale for use in MS and are also supported by preclinical or pilot clinical data.

Many drugs act on the central nervous system (CNS), with specific aims in mind. While certain categories of drugs are considered elsewhere (anaesthetic gases and vapours in Section 3, Chapter 5, hypnotics and intravenous agents in Chapter 6) other drugs acting on the CNS have been grouped here. Anti-emetic agents are considered in detail, with specific pharmacology of individual agents to reflect their direct relevance to the practice of anaesthesia. Anti-emetic agents The causes of nausea and vomiting (NV) are legion, as illustrated by Figure CN1, and anti-emetic therapy is most effective when directed at the likely origin. Postoperative nausea and vomiting (PONV) is a specific entity. Its treatment is more appropriately directed when other risk factors are considered, and these are summarised in Figure CN2. Two distinct sites in the CNS, the vomiting centre and the chemoreceptor trigger zone, are implicated in the causes of NV. The chemoreceptor trigger zone lies in the area postrema outside the blood–brain barrier and possesses dopaminergic (D 2 ) and serotonergic (5-hydroxytryptamine, 5-HT 3 ) receptors. In contrast, the vomiting centre is a complex entity located in the dorsolateral reticular formation of the brain stem that possesses 5-HT 3 , D 2 and muscarinic (M 3 ) receptors. Histaminic (H 1 ) and neurokinin (NK 1 ) receptors are located in the nucleus of the tractus solitarius, which integrates afferent signals associated with emesis. The interaction of various drugs with these sites is shown in Figure CN3.

The irritable bowel syndrome (IBS) is the prototypic functional bowel disorder in terms of its heterogeneous nature, multifactorial pathogenesis and requirement for individualized diagnosis and treatment. The surge of scientific interest in IBS during the past two decades has brought increased awareness that both the traditional biomedical model of disease and a purely psychiatric explanation are inadequate keys to understanding and treating IBS. Most researchers and clinicians accept the ability of the multinational Rome symptom criteria to identify IBS in epidemiological surveys and play a dominant diagnostic role in clinical practice. Many patients with symptoms typical of IBS can be confidently diagnosed after the performance of flexible sigmoidoscopy and a complete blood count. IBS is a common functional disorder which is best understood from the biopsychosocial concept of illness in which both biological and psychosocial factors influence symptom experience, behavior and outcome.