Barbiturate withdrawal is caused by a sudden discontinuation of short and intermediate-acting barbiturates after a prolonged period of heavy use. This leads to the classical signs and symptoms of withdrawal resembling alcohol withdrawal syndrome. Diagnosis of the condition is based on a detailed history and clinical findings. Laboratory tests to detect blood levels of barbiturates are usually unhelpful.
Depending on their duration of action, barbiturates are classified as short, ultra short, intermediate and long-acting  . Of these, the short and intermediate-acting barbiturates like pentobarbital and secobarbital  are often associated with withdrawal symptoms and signs. Barbiturate withdrawal can occur following the sudden cessation of the drug. This leads to a withdrawal syndrome identical to alcohol withdrawal with delirium tremens and can even be life-threatening in some patients.
Within a day after withdrawal of barbiturates, individuals develop restlessness, weakness, and tremulousness. Symptoms progressively increase on the second day with exaggerated deep tendon reflexes. Seizures can develop within 48 to 72 hours in patients who were on very high doses of barbiturates. This can even progress to status epilepticus and sometimes death . Other clinical features like confusion, delirium, auditory and visual hallucinations, hyperpyrexia, circulatory collapse, and dehydration may occur between 48 to 120 hours after withdrawal .
Compared to alcohol withdrawal syndrome, barbiturate withdrawal is more variable and delayed  and patients can develop multiple seizures and delirium.
History is the most important part of the workup, with the diagnosis being based on clinical findings. It is essential to diagnose barbiturate withdrawal quickly, otherwise seizures, delirium, and death may follow . According to the Diagnostic and Statistical manual of mental disorders (DSM) - 5 , the criteria for barbiturate withdrawal are the following:
It is important for the physician to elicit a history of the exact barbiturate used/abused, duration of illicit usage or abuse, when it was last ingested, was the drug discontinued suddenly or accidentally, treatment received for withdrawal symptoms, and whether other substances like alcohol were also ingested.
Urine toxicology is performed in all cases and may help to detect other substances consumed along with the barbiturates. Most laboratories are unable to measure blood levels of barbiturates except phenobarbital. Routine laboratory tests like a complete blood cell count (CBC), serum electrolytes, blood urea nitrogen, serum creatinine, and blood glucose levels are obtained to exclude metabolic syndromes which cause symptoms identical to barbiturate withdrawal. Arterial blood gas (ABG) analysis is useful to diagnose metabolic acidosis and respiratory failure while serum lactic acid level helps to evaluate perfusion at the cellular level. A urine pregnancy test should be performed in all women in the childbearing age group.