Drug Index

Amphetamine

 
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Synonym :

Dextroamphetamine

Mechanism :

Amphetamines are non-catecholamine, sympathomimetic amines with CNS stimulant activity. Peripheral actions include elevations of systolic and diastolic blood pressure, weak bronchodilator and respiratory stimulant action.


Indication :

• Narcolepsy

• Attention Deficit Disorder with Hyperactivity


Contraindications :

Advanced arteriosclerosis, symptomatic cardiovascular disease, moderate to severe hypertension, hyperthyroidism, known hypersensitivity or idiosyncrasy to the sympathomimetic amines, glaucoma, agitated states are contraindications.

For 14 days following the administration of monoamine oxidase inhibitors hypertensive rises may result.


Dosing :

Oral

Narcolepsy:

6-12 years: Initial: 5 mg once daily on waking up.; increase by 5 mg weekly until optimal response.

≥12 years: 10 mg/day initially; increase by 10 mg weekly. Maximum dose: 60 mg once daily.

ADHD:

<3 years: Not recommended.

3 to 5 years: Start with 2.5 mg daily; increase by 2.5 mg weekly until optimal response Maximum dose: 40 mg once daily.

≥6 years: 5 mg/day initially, increase by 5 mg weekly until optimal response. Maximum dose: 40 mg/day.


Adverse Effect :

Tachycardia, palpitations, hypertension, cardiomyopathy (on chronic use), psychosis, dizziness, insomnia, euphoria, restlessness, dysphoria, tremor, headaches, motor and phonic tics exacerbation, Tourette’s syndrome, dryness of mouth, unpleasant taste, diarrhea, constipation, anorexia, weight loss, urticaria, impotence, changes in libido.


Interaction :

Acidifying Agents: Gastrointestinal acidifying agents (guanethidine, reserpine, glutamic acid HCl, 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.
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 molecules, thereby decreasing urinary excretion.
Tricyclic Antidepressants: Amphetamines may enhance the activity of tricyclic or sympathomimetic agents.
MAO Inhibitors: MAO 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.
Antihypertensives: Amphetamines may antagonize the hypotensive effects of antihypertensives.
Chlorpromazine: Chlorpromazine blocks a 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 antiobesity and 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 the intestinal absorption of phenobarbital.
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.


07/17/2019 21:30:55 Amphetamine
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