Phenobarbital

May be taken with or without food.

Acute intermittent porphyria or history of manifest or latent porphyria; severe respiratory depression. IV: History of sedative-hypnotic substance use disorder; nephritic patients (large doses). Severe renal and hepatic impairment.

Patient with respiratory disease (including status asthmaticus), acute or chronic pain, history of drug abuse or alcoholism, severe anaemia (use is not recommended if due to folate deficiency) or history of haematological disease (particularly chronic anaemia), cardiac disease, hypotension or shock, depression or suicidal tendencies, diabetes mellitus, hyperthyroidism, hypoadrenalism, fever. Avoid abrupt withdrawal. Not indicated for treatment of absence seizures. Consider supplementation of vitamin D and Ca as necessary. Debilitated patients. Mild to moderate renal and hepatic impairment. Children and elderly. Pregnancy and lactation. Patient Counselling This drug may cause drowsiness or reduce alertness, if affected, do not drive or operate machinery. Women of childbearing potential must use proven birth control methods during therapy and for 2 months after stopping the treatment. Consider using other reliable contraceptive methods recommended by the doctor as hormonal contraceptives may be ineffective. Monitoring Parameters Pregnancy test may be considered in women of childbearing potential to rule out pregnancy before initiating treatment. Monitor serum phenobarbital concentration (if clinically indicated); LFTs, CBC with differential, and renal function (periodically). Observe for signs and symptoms of suicidality or unusual changes in behaviour. Assess for history of addiction or suicidal ideation; CNS status and seizure activity. For IV inj: Monitor blood pressure, heart and respiratory rate, and administration site.

Significant: Respiratory depression (particularly IV use), suicidal ideation and behaviour; paradoxical responses (including agitation, hyperactivity); drug dependence, decreased BMD, increased risk of fractures (prolonged use). Blood and lymphatic system disorders: Agranulocytosis, megaloblastic anaemia, thrombocytopenia. Cardiac disorders: Bradycardia. Gastrointestinal disorders: Nausea, vomiting. General disorders and administration site conditions: Lethargy, hangover effect; inj site reactions (IV/IM). Hepatobiliary disorders: Hepatitis, cholestasis. Musculoskeletal and connective tissue disorders: Dupuytren's contracture, arthralgia, frozen shoulder, osteomalacia, rickets; osteopenia, osteoporosis (prolonged use). Nervous system disorders: Drowsiness, ataxia, nystagmus. Psychiatric disorders: Mental depression, hallucination; confusion, restlessness (in elderly); memory and cognitive impairment; behavioural disturbances (in children). Skin and subcutaneous tissue disorders: Maculopapular, morbilliform or scarlatiniform rashes. Vascular disorders: Hypotension, syncope.
Potentially Fatal: Rarely, Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis.

Concurrent use with MAOIs, SSRIs, and TCAs may antagonise antiepileptic activity of phenobarbital by reducing the convulsive threshold. May result in additive CNS depressant effects when used concomitantly with other CNS depressants (e.g. antihistamines, narcotics, tranquilisers). Increased plasma concentration with oxcarbazepine, phenytoin, methylphenidate, chloramphenicol, valproic acid or Na valproate. May decrease plasma concentration with vigabatrin or folic acid. May decrease efficacy with memantine. May reduce the plasma concentrations of disopyramide, quinidine, chloramphenicol, doxycycline, metronidazole, rifampicin, anticoagulants (e.g. dicoumarol), chlorpromazine, paroxetine, mianserin, TCAs, carbamazepine, lamotrigine, tiagabine, zonisamide, primidone, ethosuximide, antifungals (e.g. itraconazole, posaconazole, griseofulvin, voriconazole), aripiprazole, antivirals (e.g. abacavir, amprenavir, darunavir, lopinavir, indinavir, nelfinavir, saquinavir), clonazepam, aprepitant, β-blockers (e.g. metoprolol, timolol), Ca channel blockers (e.g. felodipine, diltiazem, verapamil, nifedipine), digoxin, ciclosporin, tacrolimus, corticosteroids, etoposide, irinotecan, eplerenone, haloperidol, gestrinone, toremifene, methadone, montelukast, theophylline, sodium oxybate, thyroid hormones, tibolone, tropisetron, vitamin D. May reduce the effect of oral contraceptives containing estrogen and/or progestogen. May increase the metabolism of paracetamol which may lead to reduced effect and increased risk of hepatotoxicity.

Anticonvulsants / Hypnotics & Sedatives

N03AA02 - phenobarbital ; Belongs to the class of barbiturates and derivatives antiepileptics.