INDICATIONS     CONTRA-INDICATIONS     DOSAGE     SIDE-EFFECTS     PREGNANCY     OVERDOSE     IDENTIFICATION     PATIENT INFORMATION

Logo LETHYL® -15, -30, -60 TABLETS

SCHEDULING STATUS:
S5

PROPRIETARY NAME
(and dosage form):

LETHYL® -15, -30, -60 TABLETS

COMPOSITION:
Each tablet contains:
15 mg, 30 mg or 60 mg
Phenobarbitone.

PHARMACOLOGICAL CLASSIFICATION:
A 2.3 - Barbiturates

PHARMACOLOGICAL ACTION:
Phenobarbitone is a long acting barbiturate acting by depression of the central nervous system. It is readily absorbed from the gastro-intestinal tract and the onset of action is approximately 1 hour. Excretion is mainly in the unchanged form in the urine. It is 40% to 60% bound to plasma proteins and bound to a similar extent in tissues including the brain. The plasma half-life is about 100 hours in adults, it is somewhat longer in neonates, while it is shorter and more variable in children.

INDICATIONS:
It is used as a sedative and hypnotic in nervous insomnia and anxiety states and for the relief of migraine.

CONTRA-INDICATIONS:
Hypersensitivity to phenobarbitone or the barbiturates.
It is contra-indicated in cases of severe impairment of hepatic, renal or respiratory function and in patients with acute porphyria.

DOSAGE AND DIRECTIONS FOR USE:
Adults:        30-120 mg three times a day
Children: 2-5 years 15-30 mg three times a day
  6-12 years 15-120 mg three times a day

SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
The most frequent side-effect is sedation, but this often becomes less marked with continued administration. Phenobarbitone may produce subtle mood changes and impairment of cognition and memory which may not be apparent without testing. Mental depression may occur.
Prolonged administration may occasionally result in folate deficiency or hypocalcaemia; less frequently, megaloblastic anaemic or osteomalacia have been reported.
At high doses nystagmus and ataxia may occur and the typical barbiturate-induced respiratory depression may become severe.
Hypersensitivity reactions occur in a small proportion of patients; skin reactions are reported in 1-3% of patients receiving phenobarbitone and are most commonly maculopapular, morbilliform or scarlatiniform rashes. More severe reactions such as exfoliative dermatitis, erythema multiforme (or Stevens-Johnson syndrome) and toxic epidermal necrolysis occur less frequently. Hepatitis and disturbances of liver function have been reported.
Paradoxical excitement, irritability and hyperexcitability may sometimes occur, particularly in children or the elderly.
Neonatal medicine dependence and symptoms resembling vitamin K deficiency and congenital malformation have been reported in infants born to mothers who received phenobarbitone during pregnancy.
Care is to be taken when withdrawing phenobarbitone in epileptic patients.
Except in rare cases of marked hypersensitivity acute poisoning from ordinary therapeutic dosage of phenobarbitone is practically unknown. Because of slow excretion of phenobarbitone, regular administration may cause chronic poisoning due to cumulative action. This is characterised by headache, visual disturbances, depression and slurred speech.
Continued use of barbiturates can result in dependence. Withdrawal of the medicine in such cases should be cautious and gradual. Phenobarbitone causes drowsiness and patients receiving them should not take charge of vehicles or machinery where loss of attention could cause accidents.
Phenobarbitone should be administered cautiously to children and the elderly and to patients with acute pain, and in those with mental depression.
Interactions:
The activity of phenobarbitone may be enhanced by the concurrent administration of other barbiturates and sedatives, diphenoxylate, mephenesin, sulphonylureas and possibly tricyclic anti-depressants and its concomitant use with alcohol may produce very serious respiratory depression and a lowering of the lethal dose.
The medicine reduces the activity of anticoagulants of the coumarin type, antihistamines, griseofulvin and some steroid hormones by increasing the rate of metabolism of these medicines. It induces liver enzymes and changes the metabolism of many other medicines.
Phenobarbitone is incompatible with many other medicines and may reduce the activity of many medicines by increasing the rate of metabolism through induction of medicine-metabolising enzymes in liver microsomes. Valproic acid has been reported to cause rises in phenobarbitone concentrations in plasma. The anti-epileptic effect of phenobarbitone may be antagonised by the concomitant administration of antidepressants or phenothiazine antipsychotic agents.

KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF ITS TREATMENT:
Overdosage may result in coma, severe respiratory and cardiovascular depression, hypotension and shock leading to renal failure and death. Hypothermia may occur, with associated pyrexia during recovery. Skin blisters (bullae) reportedly occur in about 6% of patients with barbiturate overdose.
Following the recent ingestion of an overdose the stomach may be emptied by lavage; activated charcoal may be given. The prime objectives are then intensive symptomatic and supportive therapy with particular attention being paid to the maintenance of cardiovascular, respiratory, and renal functions and to the maintenance of the electrolyte balance.

IDENTIFICATION:
Lethyl-15 White biconvex tablets with a diameter of 4,8 mm.
Lethyl-30 White biconvex tablets with a diameter of 5,5 mm.
Lethyl-60 White biconvex tablets with a diameter of 6,4 mm.

PRESENTATION:
Lethyl-15 Securitainer packs of 1000 tablets
Lethyl-30 Securitainer packs of 100, 1000 and 5 000 tablets
Lethyl-60 Securitainer packs of 1000 tablets

STORAGE INSTRUCTIONS:
Store below 25°C and protect from light, heat and moisture.

APPLICATION NUMBERS:
Lethyl-15         B1167 (Act 101/1965)
Lethyl-30         B1163 (Act 101/1965)
Lethyl-60         B1166 (Act 101/1965)

NAME AND BUSINESS ADDRESS OF THE APPLICANT:
PHARMACARE LIMITED
7 Fairclough Road
Korsten
Port Elizabeth
6020

DATE OF PUBLICATION OF THIS PACKAGE INSERT:
05 December 1969

        G760A
        KOHLER C&P P.E.

Updated on this site: April 2003
Current: October 2005
Source: Hospital Pharmacy

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