Normal therapeutic range in blood: 0.8 to 1.5 mmol/L. RBC concentrations may correlate better with toxic symptoms.
Mild intoxication (blood levels 1.5 - 2.0 mmol/L):
(1) nausea
(2) diarrhea
(3) polyuria
(4) blurred vision
(5) muscular weakness and/or fasciculations
(6) drowsiness
(7) vertigo
(8) confusion
(9) slurred speech, dysarthria
(10) transient scotomas
(11) blackout
(12) increased deep tendon reflexes
Moderate intoxication (blood levels 2.0 - 3.0 mmol/L):
(1) myoclonic twitches or movements of entire limbs
(2) choreoathetoid movements
(3) urinary or fecal incontinence
(4) restlessness
(5) stupor or coma
(6) clinical myxedema if hypothyroid
(7) cerebellar dysfunction with ataxia
Severe intoxication (blood levels >= 3 mmol/L):
(1) epileptiform seizures
(2) cardiac arrhythmias (sinus arrest, prolongation of QTc interval
(3) hypotension
(4) peripheral vascular collapse
(5) acute respiratory distress or arrest
(6) cardiac arrest
