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Suicidal Ideation and Behaviour: Suicidal ideation and behaviour have been reported in patients treated with anti-epileptic agents in several indications. A meta-analysis of randomised placebo-controlled trials of anti-epileptic drugs has also shown a small increased risk of suicidal ideation and behaviour. The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for phenobarbitone.
Therefore, patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered. Patients and caregivers of patients should be advised to seek medical advice should signs of suicidal ideation or behaviour emerge.
Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN): Life-threatening cutaneous reactions Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported with the use of phenobarbitone. Patients should be advised of the signs and symptoms and monitored closely for skin reactions. The highest risk for occurrence of SJS or TEN is within the first weeks of treatment.
If symptoms or signs of SJS or TEN (e.g., progressive skin rash often with blisters or mucosal lesions) are present, phenobarbitone treatment should be discontinued. The best results in managing SJS and TEN come from early diagnosis and immediate discontinuation of any suspect drug. Early withdrawal is associated with a better prognosis.
If the patient has developed SJS or TEN with the use of phenobarbitone, phenobarbitone must not be restarted in this patient at any time.
Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS): Multi-organ hypersensitivity reactions, also known as drug reaction with eosinophilia and systemic symptoms (DRESS), have occurred with the use of phenobarbitone. Some have been fatal or life-threatening. DRESS typically, although not exclusively, presents with fever, rash, and/or lymphadenopathy in association with other organ system involvement, such as hepatitis, nephritis, hematologic abnormalities, aseptic meningitis, myocarditis, or myositis, sometimes resembling an acute viral infection. Eosinophilia is often present. This disorder is variable in its expression and other organ systems not noted here may be involved. The syndrome shows wide spectrum of clinical severity and may rarely lead to disseminated intravascular coagulation and multi-organ failure.
It is important to note that early manifestation of hypersensitivity (e.g fever, lymphadenopathy) may be present even though rash is not evident. If such signs or symptoms present, the patient should be evaluated immediately. Phenobarbitone should be discontinued.
Bone Disorder: Long-term use of antiepileptics such as carbamazepine, phenobarbitone, phenytoin, primidone, oxcarbazepine, lamotrigine, and sodium valproate are associated with a risk of decreased bone mineral density that may lead to weakened or brittle bones. Discontinuation of phenobarbitone should be considered if evidence of significant bone marrow depression develops.
Care should be used in the following situations: Patients with the rare hereditary problems of galactose intolerance, the lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine; Respiratory depression (avoid if severe); Young, debilitated or senile patients; Renal impairment; Existing liver disease; Sudden withdrawal should be avoided as severe withdrawal syndrome (rebound insomnia, anxiety, tremor, dizziness, nausea, fits and delirium) may be precipitated; Acute chronic pain-paradoxical excitement may be induced or important symptoms masked; Prolonged use may result in dependence of the alcohol-barbiturate type. Care should be taken in treating patients with a history of drug abuse or alcoholism.
Labour and Delivery: Full anaesthetic doses of barbiturates decrease the force and frequency of uterine contractions - use of barbiturates during labour may cause respiratory depression in the neonate, especially the premature neonate, because of immature hepatic function.
Effects on Ability to Drive and Use Machines: Phenobarbitone may impair the mental and/or physical abilities required for the performance of potentially hazardous tasks such as driving a car or operating machinery. Patients should be advised to make sure they are not affected before undertaking any potentially hazardous tasks.
Use in Children: Some children may react to barbiturates with paradoxical excitement.
Use in the Elderly: Geriatric patients may be more sensitive to the effects of barbiturates. They may react to usual doses of barbiturates with excitement, confusion or depression.
