Other
CII
Rx Only
P5557-2 04/07
Acidifying agents – Gastrointestinal acidifying agents (guanethidine, reserpine, glutamic acid hydrochloride, ascorbic acid, fruit juices, etc.) lower absorption of amphetamines. Urinary acidifying agents (ammonium chloride, sodium acid phosphate, etc.) increase the concentration of the ionized species of the amphetamine molecule, thereby increasing urinary excretion. Both groups of agents lower blood levels and efficacy of amphetamines.
Adrenergic blockers – Adrenergic blockers are inhibited by amphetamines.
Alkalinizing agents – Gastrointestinal alkalinizing agents (sodium bicarbonate, etc.) increase absorption of amphetamines. Urinary alkalinizing agents (acetazolamide, some thiazides) increase the concentration of the non-ionized species of the amphetamine molecule, thereby decreasing urinary excretion. Both groups of agents increase blood levels and therefore potentiate the actions of amphetamines.
Antidepressants, tricyclic – Amphetamines may enhance the activity of tricyclic or sympathomimetic agents; d-amphetamine with desipramine or protriptyline and possibly other tricyclics cause striking and sustained increases in the concentration of d-amphetamine in the brain; cardiovascular effects can be potentiated.
MAO inhibitors – MAOI antidepressants, as well as a metabolite of furazolidone, slow amphetamine metabolism. This slowing potentiates amphetamines, increasing their effect on the release of norepinephrine and other monoamines from adrenergic nerve endings; this can cause headaches and other signs of hypertensive crisis. A variety of neurological toxic effects and malignant hyperpyrexia can occur, sometimes with fatal results.
Antihistamines – Amphetamines may counteract the sedative effect of antihistamines.
Antihypertensives – Amphetamines may antagonize the hypotensive effects of antihypertensives.
Chlorpromazine – Chlorpromazine blocks dopamine and norepinephrine reuptake, thus inhibiting the central stimulant effects of amphetamines, and can be used to treat amphetamine poisoning.
Ethosuximide – Amphetamines may delay intestinal absorption of ethosuximide.
Haloperidol – Haloperidol blocks dopamine and norepinephrine reuptake, thus inhibiting the central stimulant effects of amphetamines.
Lithium carbonate – The stimulatory effects of amphetamines may be inhibited by lithium carbonate.
Meperidine – Amphetamines potentiate the analgesic effect of meperidine.
Methenamine therapy – Urinary excretion of amphetamines is increased, and efficacy is reduced, by acidifying agents used in methenamine therapy.
Norepinephrine – Amphetamines enhance the adrenergic effect of norepinephrine.
Phenobarbital – Amphetamines may delay intestinal absorption of phenobarbital; co-administration of phenobarbital may produce a synergistic anticonvulsant action.
Phenytoin – Amphetamines may delay intestinal absorption of phenytoin; co-administration of phenytoin may produce a synergistic anticonvulsant action.
Propoxyphene – In cases of propoxyphene overdosage, amphetamine CNS stimulation is potentiated and fatal convulsions can occur.
Veratrum alkaloids – Amphetamines inhibit the hypotensive effect of veratrum alkaloids.
TREATMENT-Consult with a Certified Poison Control Center for up-to-date guidance and advice. Management of acute amphetamine intoxication is largely symptomatic and includes gastric lavage, administration of activated charcoal, administration of a cathartic, and sedation. Experience with hemodialysis or peritoneal dialysis is inadequate to permit recommendation in this regard. Acidification of the urine increases amphetamine excretion, but is believed to increase risk of acute renal failure if myoglobinuria is present. If acute, severe hypertension complicates amphetamine overdosage, administration of intravenous phentolamine has been suggested. However, a gradual drop in blood pressure will usually result when sufficient sedation has been achieved.
Chlorpromazine antagonizes the central stimulant effects of amphetamines and can be used to treat amphetamine intoxication.
Narcolepsy: Usual dose is 5 mg to 60 mg per day in divided doses, depending on the individual patient response.
Narcolepsy seldom occurs in pediatric patients under 12 years of age; however, when it does, dextroamphetamine sulfate tablets may be used. The suggested initial dose for patients aged 6 to 12 is 5 mg daily; daily dose may be raised in increments of 5 mg at weekly intervals until optimal response is obtained. In patients 12 years of age and older, start with 10 mg daily; daily dosage may be raised in increments of 10 mg at weekly intervals until an optimal response is obtained. If bothersome adverse reactions appear (e.g., insomnia or anorexia), dosage should be reduced. Give first dose on awakening; additional doses (1 or 2) at intervals of 4 to 6 hours.
Attention Deficit Disorder with Hyperactivity: Not recommended for pediatric patients under 3 years of age.
In pediatric patients from 3 to 5 years of age, start with 2.5 mg daily, by tablet; daily dosage may be raised in increments of 2.5 mg at weekly intervals until optimal response is obtained.
In pediatric patients 6 years of age and older, start with 5 mg once or twice daily; daily dosage may be raised in increments of 5 mg at weekly intervals until optimal response is obtained. Only in rare cases will it he necessary to exceed a total of 40 mg per day.
Give first dose on awakening: additional doses (1 or 2) at intervals of 4 to 6 hours.
Where possible, drug administration should be interrupted occasionally to determine if there is a recurrence of behavioral symptoms sufficient to require continued therapy.