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White 8mm normal convex tablets each containing 5mg dexamphetamine sulphate.
Dexamphetamine, the dextrorotatory isomer of amphetamine, is an indirect-acting sympathomimetic amine with central stimulant and anorectic activity. It increases motor activity and mental alertness, and diminishes drowsiness and a sense of fatigue.
In children with attention-deficit hyperactivity disorder, dexamphetamine decreases motor restlessness and enhances the ability to pay attention.
Amphetamine facilitates the action of dopamine and norepinephrine by blocking reuptake from the synapse, inhibits the action of monoamine oxidase (MAO), and facilitates the release of catecolamines. It may also stimulate inhibitory autoreceptors in the substantia nigra and ventral tegmentum.
Dexamphetamine sulphate is readily absorbed from the gastro-intestinal tract and rapidly distributed into most of the body tissues with high concentrations in the brain and CSF.
The biotransformation is hepatic and the biological half-life is 10 to 12 hours in adults and 6 to 8 hours in children. The main metabolic reaction is oxidative deamination to form phenylacetone, which is then oxidised to benzoic acid and conjugated with glycine to form hippuric acid.
The elimination is mainly renal. Urinary elimination is pH dependent and enhanced in acid urine. A considerable fraction may be excreted in the urine unchanged. Under uncontrolled urinary pH conditions, about 30% of the dose is excreted unchanged in the urine in 24 hours and a total of about 90% of the dose is excreted in 3 to 4 days.
Dexamphetamine sulphate 5mg Tablets are indicated in the treatment of well-established and proven narcolepsy. It is also indicated for children with refractory hyperkinetic states under the supervision of a physician specialising in child psychiatry.
| For narcolepsy : | |
|---|---|
| Adults : | Oral, 5 to 20 mg a day in divided doses as needed and tolerated. The usual starting dose is 5mg a day, given in divided doses. Doses may be increased if necessary by 5mg a day at weekly intervals to a suggested maximum of 20mg a day. |
| Elderly : | Start with 5mg a day, and increase by increments of 5 mg at weekly intervals. |
| Children : | |
| - Children up to 6 years of age | Dosage has not been established. |
| - Children 6 to 12 years of age | Oral, 5mg a day, the dosage being increased by 5 mg a day at one-week intervals until the desired response is obtained or until the adult dose is reached. |
| For attention-deficit hyperactivity disorders : | |
| Children : | |
| - Children up to 3 years of age | Use is not recommended. |
| - Children 3 to 5 years of age | Oral, 2.5mg once a day, the dosage being increased by 2.5mg a day at one-week intervals until the desired response is obtained. |
| - Children 6 years of age and over | Oral, 5mg one or two times a day, the dosage being increased by 5mg a day at one-week intervals until the desired response is obtained. |
Dexamphetamine sulphate tablets are contraindicated in patients with known hypersensitivity to amphetamines and other sympathomimetics. Do not use in patients during, or for 14 days after, treatment with MAO inhibitor, in those with a history of drug abuse, with symptomatic cardiovascular diseases and/or moderate to severe hypertensive disease, in those suffering from hyperthyroidism or hyperexcitability or in those with glaucoma.
Dexamphetamine is contra-indicated in patients with extrapyramidal disorders. It should be avoided in pregnant women or breast feeding mothers.
Use with caution in patients sensitive to amphetamines and other sympathomimetics.
Use of dexamphetamine sulphate during early pregnancy may be associated with an increased risk of congenital malformations, especially in the cardiovascular system and biliary tract. Reproductive studies in animals have suggested both an embryotoxic and a teratogenic potential when amphetamines were administered at high multiples of the human dose. Infants born to mothers dependent on amphetamines have an increased risk of premature delivery and low birth weight.
Dexamphetamine is excreted in breast milk, therefore, it should be avoided in breast-feeding mothers.
Prolonged administration of dexamphetamine sulphate to children may inhibit growth. Height and weight in children should be monitored. Psychotic children may experience exacerbation of symptoms of behaviour disturbance and thought disorder. It provokes or exacerbates motor and vocal tics and Tourette's syndrome, necessitating clinical evaluation before administration of dexamphetamine sulphate.
No data is available on relationship of age to the effects of dexamphetamine in geriatric patients.
It should be given with caution to patients with mild hypertension, impaired kidney function, or unstable personality. Prolonged high doses may need gradual withdrawal as abrupt cessation may produce fatigue and mental depression.
It should be given with caution to patients with epilepsy as dexamphetamine may reduce the convulsive threshold. Alcoholic beverages should be avoided. Dexamphetamine may impair patients' ability to drive or to operate machinery.
The side-effects of dexamphetamine are commonly symptoms of overstimulation of the central nervous system and include insomnia, nervousness, restlessness, irritability, and euphoria that may be followed by fatigue and depression. There may be dryness of the mouth, anorexia, abdominal cramps and other gastro-intestinal disturbances, headache, dizziness, tremor, sweating, tachycardia, palpitations, increased or sometimes decreased blood pressure, altered libido, and impotence. Rarely cardiomyopathy has occurred with chronic use.
Tolerance can develop to some of Dexamphetamine's central effects leading to increased doses and habituation. Abrupt cessation after prolonged treatment or abuse of dexamphetamine has been associated with fatigue, hyperphagia and mental depression.
Dexamphetamine may also diminish the effects of guanethidine and similar antihypertensive agents, hence concurrent use should be avoided.
Concurrent use of insulin or oral diabetic agents may increase the possibility of hyperglycemia. Dosage adjustment of either or both medications may be necessary.
Central stimulant effects of amphetamines may be antagonised by lithium. Lithium and α-methyltyrosine may antagonise the effects of amphetamines.
The urinary excretion of dexamphetamine is reduced by urinary alkalinisers which may enhance or prolong its effects. Its excretion is increased by urinary acidifiers.
To avoid precipitating a hypertensive crisis, it should not be given to patients being treated with a monoamine oxidase inhibitor or within 14 days of stopping such treament.
Avoid concurrent use of beta blockers as this may produce severe hypertension.
Although tricyclic antidepressants may be used concurrently with amphetamines for therapeutic effect, concurrent use may potentiate cardiovascular effects due to release of norepinephrine, possibly resulting in arrhythmias, tachycardia, or severe hypertension or hyperpyrexia; close monitoring is required and dosage adjustments may be necessary.
Disulfiram may inhibit the metabolism and excretion of dexamphetamine.
In acute overdosage, the adverse effects are accentuated and may be accompanied by hyperpyrexia, mydriasis, hyperreflexia, chest pain, cardiac arrhythmias, confusion, panic states, aggressive behaviour, hallucinations, delirium, convulsions, respiratory depression, coma, circulatory collapse and death. Individual patient response may vary widely and toxic manifestations may occur at relatively low doses.
Since, there is no specific antidote for overdosage with dexamphetamine, treatment is symptomatic and supportive with possible utilisation of the following :
Store below 25°C in an air tight container. Protect from light. Do not refrigerate.
Controlled Drug B2.
Package Quantities
Bulk pack of 1000 tablets in white plastic bottles.
Further Information
Distributed by -
PSM Healthcare Ltd
PO Box 76-401
Manukau
AUCKLAND
TELEPHONE : 09 277 7751
FAX : 09 277 7544