Pharmacological Modulation of the State of Awareness in Patients with Disorders of Consciousness: An Overview
The neurobiological approach to consciousness moves from the assumption that all phenomenal experiences are based on neuronal
activity in the brain. Consciousness has two main components: wakefulness and awareness. While it may be relatively easy to determine
the neuronal correlates of wakefulness, it is not the same for awareness, of which the neural correlates are poorly understood.
Knowledge of the circuitry and the neurochemistry of the sleep/wake condition is necessary but not sufficient to understand the circuitry
and neurochemistry of consciousness. Disorders of consciousness (DOCs) include coma, vegetative state and minimally conscious state.
The study of DOCs and of the electrophysiological changes underlying general anaesthesia-induced loss of consciousness may help in
understanding the neuronal correlates of consciousness. In turn, the understanding of the neural bases of consciousness may help in designing
interventions aimed at restoring consciousness in DOC patients. Sporadic cases of recovery from a DOC have been reported after
the administration of various pharmacological agents (baclofen, zolpidem, amantadine etc.). This review provides an overview of such
drugs, which are from various and diverging classes but can be grouped into two main categories: CNS stimulants and CNS depressants.
The available data seem to suggest an awakening effect obtained with CNS depressants rather than stimulants, the latter being more effective
at improving functional cognitive and behavioral recovery in patients who have spontaneously regained an appreciable level of
consciousness. There is a need for more rigorous systematic trials and further investigation of the above treatments, with particular attention
paid to their mechanisms of action and the neurotransmitters involved.
Keywords: Consciousness, vegetative state, coma, minimally conscious state, awakenings, drugs, pharmacology.
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