The prognostic and diagnostic utility of a serum lactate concentration in the initial evaluation of drug overdose is historically controversial. Lactate concentration is a useful prognostic indicator for mortality in both medical/surgical patients and undifferentiated ICU patients. Current guidelines for the initial approach to management of the patient with a drug overdose do not include routine evaluation of serum for a lactate concentration. However, lactate concentration is an established prognostic marker for the evaluation of patients with elevated anion gap metabolic acidosis, selected drug overdoses (metformin and acetaminophen), selected chronic drug toxicities (stadivudine), and chemical poisoning (aluminum phosphide and cyanide) [8-10].
As the report of national drug and poisoning information center (DPIC) of Iran provided, 60% of all contacts per year are related to poisoning . Lactic acidosis is the condition where lactate concentration increase instantly to more than 5 mmol/dL. Type A of lactic acidosis occurs in oxygen distribution dysfunction due to hypotension or cyanosis . Type B lactic acidosis occurs in sepsis, liver dysfunction, diabetes, and drugs such as biguanides, acetaminophen, and sorbitol [6,9].
Creatine kinase supplies energy in body organs with different types in brain (CK1), myocardium (CK2), and muscle (CK3) whose change is considered to be due to organ damages . Usually, existence of CK in blood defines the organ injuries including myocardial infarctions, rhabdomyolysis, autoimmune myositis, and kidney injuries .
Our results are in accordance with those reported by Lee et al in paraquat-poisoned patients in early stages of poisoning  although they did not evaluate CK level. Manini and colleagues evaluated 50 cases and 100 controls among acutely-poisoned patients and determined that lactate was an excellent prognostic factor in poisoned patients . They declared that using ROC analysis, initial venous lactate concentrations obtained in the ED had outstanding diagnostic test characteristics. By maximizing the sum of sensitivity and specificity, selection of optimal integer cut points for lactate concentration occurred at 3.0 (27 mg/dL) and 5.0 mmol/L  which is very close to our results (the most sensitive cutoff point of 26.5 mg/dL).
Talbot and assistants defined cryptic shock as condition of shock in which blood pressure is normal but lactate is increased. They mentioned that hypoxia or toxins could destroy ATP since phosphorylation chain accelerates causing in accumulation of pyruvate and increased in Lactate level . However, in a study on carbon monoxide-poisoned patients, although it was shown that serum lactate increases at the beginning of CO poisoning and this increase is compatible with patients’ blood CO level and severity of neurologic symptoms, there was no statistically significant difference in neurological symptoms in study groups. This study concluded that serum lactate was not a beneficial criterion for intoxication determining (Spearman's test r=0.3)  that is not in line with our study. Mozaffari et al also mentioned that serum lactate was higher in patients who had died in toxicology ICU although their main focus was on ventilator-associated pneumonia and no direct correlation had been checked .
We also evaluated serum CK in accordance with serum lactate between survivors and non-survivors and tried to set a specific cut-off point to simplify evaluation of clinical condition of each patient and accelerate medical actions. Finally, lactate and CK level were higher in non-survivors with an acceptable cut-off point set to differentiate between these two group. It seems that Lactate and CK can be used in determination of prognosis in acute poisonings as Manini and colleagues had previously claimed .