Final answer:
Early manifestations of lithium toxicity include nausea and muscle weakness, which are common symptoms. It's important to recognize these early signs to avoid severe complications like renal failure.
Step-by-step explanation:
The early manifestations of lithium toxicity include several symptoms that impact both neurological and gastrointestinal functions. Some of the early signs involve Nausea, Muscle Weakness, Agitation, Anxiety, Sleep problems, Vomiting, Abnormal heart rhythms, and Low blood pressure (hypotension). These manifestations can vary amongst individuals, but nausea and muscle weakness are particularly notable as they are commonly recognized in the early stages of lithium toxicity. It is crucial to be aware of these early signs to prevent more severe complications, such as renal failure, which manifests at a later stage.