Amfetamine Actions

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Actions of Amfetamine in details

infoThe action of the drug on the human body is called Pharmacodynamics in Medical terminology. To produce its effect and to change the pathological process that is happening the body and to reduce the symptom or cure the disease, the medicine has to function in a specific way. The changes it does to the body at cellular level gives the desired result of treating a disease. Drugs act by stimulating or inhibiting a receptor or an enzyme or a protein most of the times. Medications are produced in such a way that the ingredients target the specific site and bring about chemical changes in the body that can stop or reverse the chemical reaction which is causing the disease.
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Amphetamines are non-catecholamine sympathomimetic amines with CNS stimulant activity. The mode of therapeutic action in ADHD is not known. Amphetamines are thought to block the reuptake of norepinephrine and dopamine into the presynaptic neuron and increase the release of these monoamines into the extraneuronal space.

How should I take Amfetamine?

infoAdministration of drug is important to know because the drug absorption and action varies depending on the route and time of administration of the drug. A medicine is prescribed before meals or after meals or along with meals. The specific timing of the drug intake about food is to increase its absorption and thus its efficacy. Few work well when taken in empty stomach and few medications need to be taken 1 or 2 hrs after the meal. A drug can be in the form of a tablet, a capsule which is the oral route of administration and the same can be in IV form which is used in specific cases. Other forms of drug administration can be a suppository in anal route or an inhalation route.

Using this medicine improperly can cause death or serious side effects on the heart.

Read all patient information, medication guides, and instruction sheets provided to you. Ask your doctor or pharmacist if you have any questions.

Follow all directions on your prescription label. Your doctor may occasionally change your dose to make sure you get the best results. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Amphetamine may be habit-forming. Never share amphetamine with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it. Selling or giving away this medicine is against the law.

You may take amphetamine with or without food. It is best to take this medicine first thing in the morning.

If your doctor changes your brand, strength, or type of stimulant medicine, your dosage needs may change. Use only the brand of this medicine your doctor has prescribed.

Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

To take the orally disintegrating tablet (Amfetamine):

  • Keep the tablet in its blister pack until you are ready to take it. Open the package and peel back the foil. Do not push a tablet through the foil or you may damage the tablet.

  • Use dry hands to remove the tablet and place it in your mouth.

  • Do not swallow the tablet whole. Allow it to dissolve in your mouth without chewing. If desired, you may drink liquid to help swallow the dissolved tablet.

While using this medicine, your doctor will need to check your progress at regular visits. Your heart rate, blood pressure, height and weight may also need to be checked often.

Amphetamine can cause unusual results with certain medical tests. Tell any doctor who treats you that you are using this medicine.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

Keep track of the amount of medicine used from each new bottle. Amphetamine is a drug of abuse and you should be aware if anyone is using your medicine improperly or without a prescription.

Throw away unused or expired amphetamine in a sealed container or bag. Ask your pharmacist where to locate a community pharmaceutical take back disposal program.

Amfetamine pharmacology

infoPharmacokinetics of a drug can be defined as what body does to the drug after it is taken. The therapeutic result of the medicine depends upon the Pharmacokinetics of the drug. It deals with the time taken for the drug to be absorbed, metabolized, the process and chemical reactions involved in metabolism and about the excretion of the drug. All these factors are essential to deciding on the efficacy of the drug. Based on these pharmacokinetic principles, the ingredients, the Pharmaceutical company decides dose and route of administration. The concentration of the drug at the site of action which is proportional to therapeutic result inside the body depends on various pharmacokinetic reactions that occur in the body.
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Mechanism Of Action

Amphetamines are non-catecholamine sympathomimetic amines with CNS stimulant activity. The mode of therapeutic action in ADHD is not known. Amphetamines are thought to block the reuptake of norepinephrine and dopamine into the presynaptic neuron and increase the release of these monoamines into the extraneuronal space.

Pharmacokinetics

Absorption

Following a single, 18.8 mg oral dose of Amfetamine in 29 healthy adult subjects in a crossover study under fasting conditions, d-amphetamine and l-amphetamine, the median (range) time to peak plasma concentrations (Tmax) were 4.0 (2 – 7) hours after dosing and peak concentration (Cmax) were 102% and 106%, respectively of the Cmax of immediate-release (IR) mixed amphetamine salts tablets. The relative bioavailability of Amfetamine compared to an equal dose of mixed amphetamine salts IR tablets is 106% of d-amphetamine and 111% for l-amphetamine.

Metabolism And Excretion

Amfetamine contains d-amphetamine and l-amphetamine in a ratio of 3.2 to 1. Following a single 18.8 mg oral dose of Amfetamine in 29 healthy adult subjects under fasting conditions, the mean (± SD) plasma terminal elimination half-life of d-amphetamine was 12.36 (± 2.95 h) hours and the mean (± SD) plasma terminal half-life for l-amphetamine was 15.12 (± 4.40 h) hours. Amphetamine is reported to be oxidized at the 4 position of the benzene ring to form 4-hydroxyamphetamine, or on the side chain A or B carbons to form alpha-hydroxy-amphetamine or norephedrine, respectively. Norephedrine and 4-hydroxy-amphetamine are both active and each is subsequently oxidized to form 4-hydroxy-norephedrine. Alpha-hydroxy-amphetamine undergoes deamination to form phenylacetone, which ultimately forms benzoic acid and its glucuronide and the glycine conjugate hippuric acid. Although the enzymes involved in amphetamine metabolism have not been clearly defined, CYP2D6 is known to be involved with formation of 4-hydroxy-amphetamine. Since CYP2D6 is genetically polymorphic, population variations in amphetamine metabolism are a possibility.

Amphetamine is known to inhibit monoamine oxidase, whereas the ability of amphetamine and its metabolites to inhibit various P450 isozymes and other enzymes has not been adequately elucidated. In vitro experiments with human microsomes indicate minor inhibition of CYP2D6 by amphetamine and minor inhibition of CYP1A2, 2D6, and 3A4 by one or more metabolites. However, due to the probability of auto-inhibition and the lack of information on the concentration of these metabolites relative to in vivo concentrations, no predications regarding the potential for amphetamine or its metabolites to inhibit the metabolism of other drugs by CYP isozymes in vivo can be made.

With normal urine pHs approximately half of an administered dose of amphetamine is recoverable in urine as derivatives of alpha-hydroxy-amphetamine and approximately another 30% to 40% of the dose is recoverable in urine as amphetamine itself. Since amphetamine has a pKa of 9.9, urinary recovery of amphetamine is highly dependent on pH and urine flow rates. Alkaline urine pHs result in less ionization and reduced renal elimination, and acidic pHs and high flow rates result in increased renal elimination with clearances greater than glomerular filtration rates, indicating the involvement of active secretion. Urinary recovery of amphetamine has been reported to range from 1% to 75%, depending on urinary pH, with the remaining fraction of the dose hepatically metabolized. Consequently, both hepatic and renal dysfunctions have the potential to inhibit the elimination of amphetamine and result in prolonged exposures. In addition, drugs that affect urinary pH are known to alter the elimination of amphetamine, and any decrease in amphetamine's metabolism that might occur due to drug interactions or genetic polymorphisms is more likely to be clinically significant when renal elimination is decreased.

Food Effect

In a study in adult volunteers to investigate the effects of a high-fat meal on the bioavailability of Amfetamine at a dose of 18.8 mg, the presence of food delayed the time to peak concentration of both d- and l-amphetamine by approximately 1 hour (fed: median [range] 5 [3 – 8] hours vs. fasted: 4 [2 – 7] hours). Overall, a high-fat meal increased the average Cmax of both isomers of Amfetamine by about 2% and decreased the AUC by 5-7% (5.7% decrease for d-amphetamine and 7.4% for l-amphetamine). These changes are not considered clinically significant.

Specific Populations

Pediatric

Following a single 10 mg oral dose of Amfetamine in 12 pediatric subjects with ADHD (aged 6-12 years) under fasting conditions, d-amphetamine and l-amphetamine peak plasma concentrations occurred at a median time of 3.9 and 4.5 hours after dosing, respectively. The mean plasma terminal elimination half-life of d-amphetamine was 10.43 (± 2.01 h) hours and the mean plasma terminal half-life for l-amphetamine was 12.14 (± 3.15 h) hours.

Alcohol Effect

There is no in vivo study conducted for the effect of alcohol on drug exposure. An in vitro dissolution study showed alcohol-induced dose dumping potential in the presence of 40% alcohol. Dose dumping was not observed in the presence of lower alcohol concentrations.

Clinical Studies

The efficacy of Amfetamine was evaluated in a laboratory classroom study conducted in 108 pediatric patients (aged 6 to 12 years) with ADHD. The study began with an open-label dose optimization period (5 weeks) with an initial Amfetamine dose of 2.5 or 5 mg once daily in the morning. The dose could be titrated weekly in increments of 2.5 to 10 mg until an optimal dose or the maximum dose of 20 mg/day was reached. Subjects then entered a 1-week randomized, double-blind treatment with the individually optimized dose of Amfetamine or placebo. At the end of the week, school teachers and raters evaluated the attention and behavior of the subjects in a laboratory classroom using the Swanson, Kotkin, Agler, M-Flynn, and Pelham (SKAMP) rating scale. SKAMP is a 13-item teacher-rated scale that assesses manifestations of ADHD in a classroom setting. Each item is rated on a 7-point impairment scale.

The primary efficacy endpoint was change from pre-dose in the SKAMP-Combined score at 4 hours post-dosing. The key secondary efficacy parameters were onset and duration of clinical effect. The change scores from pre-dose SKAMP-Combined scores at post-dose time points (1, 2, 4, 6, 8, 10, 12 and 13 hours) were used to evaluate the key secondary efficacy. Results from the double-blind, placebo-controlled week of the study are summarized in Table 3 and Figure 1.

SKAMP-Combined change scores from pre-dose demonstrated a statistically significant improvement at all time points (1, 2, 4, 6, 8, 10, 12, 13 hours) post-dosing with Amfetamine compared to placebo.

Table 3: Primary efficacy result.

Patient Counseling Information

Advise the patient to read the FDA-approved patient labeling (Medication Guide).

Controlled Substance Status/Potential For Abuse, Misuse, And Dependence

Advise patients that Amfetamine is a federally controlled substance because it can be abused or lead to dependence. Advise patients to store Amfetamine in a safe place, preferably locked, to prevent abuse. Advise patients to comply with laws and regulations on drug disposal. Advise patients to dispose of remaining, unused, or expired Amfetamine by a medicine take-back program if available.

Dosage And Administration Instructions

Provide the following instructions on administration to the patient:

  • Use with an oral dosing device or other suitable measuring device.
  • Shake the bottle of Amfetamine before each dose.
  • Measure the appropriate dose as prescribed by the physician.
  • Using the filled oral dosing syringe or measuring device, dispense Amfetamine directly into mouth.
  • Replace bottle cap and store bottle as directed.
  • Wash oral dosing syringe or measuring device after each use.
Serious Cardiovascular Risks

Advise patients of serious cardiovascular risk (including sudden death, myocardial infarction, stroke, and hypertension) with Amfetamine. Instruct patients to contact a healthcare provider immediately if they develop symptoms such as exertional chest pain, unexplained syncope, or other symptoms suggestive of cardiac disease.

Blood Pressure And Heart Rate Increases

Instruct patients that Amfetamine can cause elevations of their blood pressure and pulse rate.

Psychiatric Risks

Advise patients that Amfetamine, at recommended doses, may cause psychotic or manic symptoms, even in patients without a prior history of psychotic symptoms or mania.

Long-Term Suppression Of Growth

Advise patients that Amfetamine may cause slowing of growth and weight loss.

Circulation Problems In Fingers And Toes [Peripheral vasculopathy, including Raynaud's phenomenon]

Instruct patients beginning treatment with Amfetamine about the risk of peripheral vasculopathy, including Raynaud's phenomenon, and associated signs and symptoms: fingers or toes may feel numb, cool, painful, and/or may change color from pale, to blue, to red.

Instruct patients to report to their physician any new numbness, pain, skin color change, or sensitivity to temperature in fingers or toes.

Instruct patients to call their physician immediately with any signs of unexplained wounds appearing on fingers or toes while taking Amfetamine.

Further clinical evaluation (e.g., rheumatology referral) may be appropriate for certain patients.

Pregnancy

Advise patients to notify their healthcare provider if they become pregnant or intend to become pregnant during treatment with Amfetamine. Advise patients of the potential fetal effects from the use of Amfetamine during pregnancy.

Lactation

Patients should be advised not to breastfeed if they are taking Amfetamine.

Alcohol

Advise patients to avoid alcohol while taking Amfetamine. Consumption of alcohol while taking

Amfetamine may result in a more rapid release of the dose of amphetamine.


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The results of a survey conducted on ndrugs.com for Amfetamine are given in detail below. The results of the survey conducted are based on the impressions and views of the website users and consumers taking Amfetamine. We implore you to kindly base your medical condition or therapeutic choices on the result or test conducted by a physician or licensed medical practitioners.

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Information checked by Dr. Sachin Kumar, MD Pharmacology

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