Monitoring for cardiac effects during concurrent use of ergot alkaloids with phentermine may be advisable. Moderate Bethanechol offsets the effects of sympathomimetics at sites where sympathomimetic and cholinergic receptors have opposite effects. Major The action of sympathomimetics may be enhanced in patients receiving bretylium. Increased sensitivity to sympathomimetics should be expected in patients receiving bretylium. Moderate The combination of bromocriptine with phentermine may cause headache, tachycardia, other cardiovascular abnormalities, seizures, and other serious effects.
Concurrent use of bromocriptine and phentermine should be approached with caution. Moderate Caution and close observation should be used when formoterol is used concurrently with other adrenergic sympathomimetics, administered by any route, to avoid potential for increased cardiovascular effects. Major Bupropion is associated with a dose-related risk of seizures. Excessive use of psychostimulants, such as phentermine, may be associated with an increased seizure risk; therefore, seizures may be more likely to occur in patients receiving this weight loss aide with bupropion.
Patients should be closely monitored if this combination is necessary. Do not combine therapy with phentermine or phentermine-combinations and bupropion; naltrexone due to this risk and the duplication of therapy for weight loss. Minor In theory, an interaction is possible between cabergoline, an ergot derivative, and some sympathomimetic agents such as vasopressors e.
Use of the ergot derivative bromocriptine for lactation suppression in conjunction with a sympathomimetic i. Major Concomitant use of cardiac glycosides with sympathomimetics can cause arrhythmias because sympathomimetics enhance ectopic pacemaker activity. Caution is warranted during co-administration of digoxin and sympathomimetics. Major Sympathomimetics can antagonize the antihypertensive effects of clonidine when administered concomitantly.
Patients should be monitored for loss of blood pressure control. Minor The response to sympathomimetics may be enhanced by colchicine. Major Halogenated anesthetics may sensitize the myocardium to the effects of the sympathomimetics. Because of this, and its effects on blood pressure, phentermine should be discontinued several days prior to surgery. Moderate Use phentermine and selective serotonin reuptake inhibitors SSRIs or serotonin norepinephrine reuptake inhibitors SNRIs together with caution; use together may be safe and efficacious for some patients based on available data, provided the patient is on a stable antidepressant regimen and receives close clinical monitoring.
Regular appointments to assess the efficacy of the weight loss treatment, the emergence of adverse events, and blood pressure monitoring are recommended. Watch for excessive serotonergic effects. Phentermine is related to the amphetamines, and there has been historical concern that phentermine might exhibit potential to cause serotonin syndrome or cardiovascular or pulmonary effects when combined with serotonergic agents.
One case report describes adverse reactions with phentermine and fluoxetine. However, recent data suggest that phentermine's effect on MAO inhibition and serotonin augmentation is minimal at therapeutic doses, and that phentermine does not additionally increase plasma serotonin levels when combined with other serotonergic agents. In large controlled clinical studies, patients were allowed to start therapy with phentermine or phentermine; topiramate extended-release for obesity along with their antidepressants e.
In analyses of the results, therapy was generally well tolerated, especially at lower phentermine doses, based on discontinuation rates and reported adverse events. Because depression and obesity often coexist, the study data may be important to providing optimal therapies. Moderate Concurrent use of dronabinol, THC with sympathomimetics may result in additive hypertension, tachycardia, and possibly cardiotoxicity.
Dronabinol, THC has been associated with occasional hypotension, hypertension, syncope, and tachycardia. In a study of 7 adult males, combinations of IV cocaine and smoked marijuana, 1 g marijuana cigarette, 0 to 2. Major Coadministration of dyphylline with sympathomimetics should be approached with caution.
Coadministration may lead to adverse effects, such as tremors, insomnia, seizures, or cardiac arrhythmias, and should be avoided if possible. Major Sympathomimetics can antagonize the antihypertensive effects of adrenergic agonists when administered concomitantly. Close monitoring of blood pressure or the selection of alternative therapeutic agents may be needed.
Moderate Caution and close observation should also be used when salmeterol is used concurrently with other adrenergic sympathomimetics, administered by any route, to avoid potential for increased cardiovascular effects. Moderate Administer sympathomimetics with caution with beta-agonists such as vilanterol. The cardiovascular effects of beta-2 agonists may be potentiated by concomitant use. Monitor the patient for tremors, nervousness, increased heart rate, or other additive side effects.
Major Some, but not all, green tea products contain caffeine. Additive CNS stimulant effects are likely to occur when caffeine is coadministered with other CNS stimulants or psychostimulants. Caffeine should be avoided or used cautiously with phentermine. Major Caffeine, an active constituent of guarana, is a CNS-stimulant and such actions are expected to be additive when coadministered with other CNS stimulants or psychostimulants. Use of guarana should be avoided with amphetamine, dextroamphetamine, methylphenidate, modafinil, pemoline, pseudoephedrine, beta-agonists or other sympathomimetics.
Major Phentermine has vasopressor effects and may limit the benefit of antihypertensive agents particularly sympatholytic agents such as methyldopa. Concomitant use of phentermine with methyldopa may antagonize the antihypertensive effects of these agents. Although leading drug interaction texts differ in the potential for an interaction between phentermine and this group of antihypertensive agents, these effects are likely to be clinically significant and have been described in hypertensive patients on these medications.
Moderate Clinically significant cardiovascular effects and fatalities have been reported in association with excessive use of inhaled sympathomimetic drugs. Caution and close observation is needed if indacaterol is used concurrently with other adrenergic sympathomimetics, administered by any route, to avoid potential for increased cardiovascular effects. Moderate Sympathomimetics can antagonize the antihypertensive effects of vasodilators when administered concomitantly.
Patients should be monitored to confirm that the desired antihypertensive effect is achieved. Major Phentermine lowers the seizure threshold and should be discontinued at least 48 hours before and for at least 24 hours after intrathecal use of contrast media. Severe In general, all types of sympathomimetics and psychostimulants should be avoided in patients receiving MAOIs due to an increased risk of hypertensive crisis.
This applies to sympathomimetics including stimulants for ADHD, narcolepsy or weight loss, nasal, oral, and ophthalmic decongestants and cold products, and even respiratory sympathomimetics e. Some local anesthetics also contain a sympathomimetic e. In general, medicines containing sympathomimetic agents should not be used concurrently with MAOIs or within 14 days before or after their use. Moderate Sympathomimetic amines should be used with caution in patients with thyrotoxicosis since these patients are unusually responsive to sympathomimetic amines.
Based on the cardiovascular stimulatory effects of sympathomimetic drugs, the concomitant use of sympathomimetics and thyroid hormones can enhance the effects on the cardiovascular system. Patients with coronary artery disease have an increased risk of coronary insufficiency from either agent. Concomitant use of these agents may increase this risk further. The reduction in TSH secretion is not sustained; hypothyroidism does not occur.
Major Phentermine should not be administered during or within 14 days following the use of linezolid. Linezolid is an antibiotic that is also a weak, reversible nonselective inhibitor of monoamine oxidase MAO. Drugs that possess MAO-inhibiting activity, such as linezolid, can prolong and intensify the cardiac stimulation and vasopressor effects of phentermine which may invoke a hypertensive reaction. Additonally, phentermine has a weak ability to dose-dependently raise serotonin levels.
Linezolid has the potential for interaction with serotonergic agents, which may increase the risk for serotonin syndrome. If coadministration is necessary, closely monitor for increased blood pressure and signs of serotonin syndrome. Major The safety and efficacy of coadministration of lorcaserin with other products intended for weight loss including prescription drugs e. Some of these agents fenfluramine, dexfenfluramine are known to increase the risk for cardiac valvulopathy and pulmonary hypertension.
Coadministration of sibutramine with other serotonergic medications is contraindicated due to the risk for serotonin-related adverse effects, such as serotonin syndrome. Major Sympathomimetics can antagonize the effects of vasodilators when administered concomitantly. Patients should be monitored for reduced efficacy if taking macitentan with a sympathomimetic. Major Caution and close observation should also be used when metaproterenol is used concurrently with other adrenergic sympathomimetics, administered by any route, to avoid potential for increased cardiovascular effects.
Major Because of the potential risk and severity of serotonin syndrome, caution should be observed during co-administration of mirtazapine with other drugs that have serotonergic properties. As a drug related to the amphetamines, phentermine has the potential to cause serotonin syndrome when combined with serotonergic agents. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes e. Patients receiving this combination should be monitored for the emergence of serotonin syndrome.
Mirtazapine should be discontinued if a patient develops a combination of symptoms suggestive of serotonin syndrome. Moderate Concurrent use of nabilone with sympathomimetics e. In a study of 7 adult males, combinations of cocaine IV and smoked marijuana 1 g marijuana cigarette, 0 to 2. Major Concomitant use of nitrates with sympathomimetics can result in antagonism of the antianginal effects of nitrates. In addition, amyl nitrite can block the alpha-adrenergic effects of epinephrine, possibly precipitating tachycardia and severe hypotension.
Moderate The safety and efficacy of coadministration of phentermine with other products intended for weight loss has not been established. Severe Phendimetrazine is a phenylalkaline sympathomimetic agent. All sympathomimetics and psychostimulants, including other anorexiants, should be used cautiously or avoided in patients receiving phendimetrazine. The safety of phendimetrazine when used with other anorexiants such as phentermine is controversial and concurrent use should be avoided.
The combined use of these agents may have the potential for additive side effects, such as hypertensive crisis or cardiac arrhythmia. Similarly, phendimetrazine should not be used in combination with OTC preparations and herbal products that may contain ephedra alkaloids or Ma huang. Major Concurrent use of phentermine and phenothiazines may antagonize the anorectic effects of phentermine. In addition, psychostimulants can aggravate psychotic states. Moderate Caution and close observation should also be used when pirbuterol is used concurrently with other adrenergic sympathomimetics, administered by any route, to avoid potential for increased cardiovascular effects.
Major Because procarbazine exhibits some monoamine oxidase inhibitory MAOI activity, sympathomimetic drugs should be avoided. As with MAOIs, the use of a sympathomimetic drug with procarbazine may precipitate hypertensive crisis or other serious side effects. In the presence of MAOIs, drugs that cause release of norepinephrine induce severe cardiovascular and cerebrovascular responses. In general, do not use a sympathomimetic drug unless clinically necessary e.
If use is necessary within 2 weeks of the MAOI drug, in general the initial dose of the sympathomimetic agent must be greatly reduced. Patients should be counseled to avoid non-prescription OTC decongestants and other drug products, weight loss products, and energy supplements that contain sympathomimetic agents. Moderate The concomitant use of rasagiline and sympathomimetics was not allowed in clinical studies; therefore, caution is advised during concurrent use of rasagiline and sympathomimetics including stimulants for ADHD and weight loss, non-prescription nasal, oral, and ophthalmic decongestants, and weight loss dietary supplements containing Ephedra.
Although sympathomimetics are contraindicated for use with other non-selective monoamine oxidase inhibitors MAOIs , hypertensive reactions generally are not expected to occur during concurrent use with rasagiline because of the selective monoamine oxidase-B MAO-B inhibition of rasagiline at manufacturer recommended doses. One case of elevated blood pressure has been reported in a patient during concurrent use of the recommended dose of rasagiline and ophthalmic tetrahydrozoline.
One case of hypertensive crisis has been reported in a patient taking the recommended dose of another MAO-B inhibitor, selegiline, in combination with ephedrine. It should be noted that the MAO-B selectivity of rasagiline decreases in a dose-related manner as increases are made above the recommended daily dose and interactions with sympathomimetics may be more likely to occur at these higher doses.
Major Phentermine has vasopressor effects and may limit the benefit of antihypertensive agents particularly sympatholytic agents such as reserpine. Concomitant use of phentermine with reserpine may antagonize the antihypertensive effects of these agents. Patients should be monitored for reduced efficacy if taking riociguat with a sympathomimetic. Moderate Severe hypertensive reactions, including hypertensive crisis, have been reported in patients taking monoamine oxidase inhibitors MAOIs , such as safinamide, and sympathomimetic medications, such as phentermine.
If concomitant use of safinamide and phentermine is necessary, monitor for hypertension and hypertensive crisis. Selective serotonin reuptake inhibitors: One case report has been received of adverse reactions with phentermine and fluoxetine. Because depression and obesity often coexist, the study data may be important to providing optimal co-therapies.
Patients should be monitored for reduced efficacy if taking selexipag with a sympathomimetic. Serotonin norepinephrine reuptake inhibitors: Severe Sibutramine is contraindicated in patients taking other centrally-acting appetite suppressant drugs, such as phentermine. In addition, many of these agents enhance central serotonergic activity by various mechanisms. Concurrent use of sibutramine with other serotonergic agents may increase the potential for serotonin syndrome or neuroleptic malignant syndrome-like reactions.
Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes e. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome. Severe Because phentermine is a sympathomimetic and anorexic agent, it should not be used in combination with other psychostimulants.
John's Wort, Hypericum perforatum: John's wort Hypericum perforatum may reduce the neuronal uptake of monoamines and should be used cautiously with sympathomimetics. Moderate Caution is warranted with the concurrent use of tedizolid and phentermine. Tedizolid is an antibiotic that is also a weak reversible, non-selective inhibitor of MAO which could potentially prolong and intensify the cardiac stimulation and vasopressor effects of phentermine.
Phentermine should not be administered during or within 14 days following the use of drugs with MAO-inhibiting activity. Moderate Concomitant use of sympathomimetics with beta-agonists might result in additive cardiovascular effects such as increased blood pressure and heart rate. Moderate Concurrent administration of theophylline or aminophylline with some sympathomimetics can produce excessive stimulation and effects such as nervousness, irritability, or insomnia. Seizures or cardiac arrhythmias are also possible.
Major Sympathomimetics can antagonize the vasodilatory effects of antihypertensive agents when administered concomitantly. Major Sympathomimetics can antagonize the antihypertensive effects of vasodilators when administered concomitantly. Also, vasodilators can antagonize pressor responses to epinephrine. Moderate Use phentermine and vilazodone together with caution; use together might be efficacious for some patients based on available data, provided the patient is on a stable antidepressant regimen and receives close clinical monitoring.
One case report describes adverse reactions with phentermine and the antidepressant fluoxetine. In large controlled clinical studies, patients were allowed to start therapy with extended-release phentermine or extended-release phentermine combinations for obesity along with their antidepressants e. Moderate Use phentermine and vortioxetine together with caution; use together may be safe and efficacious for some patients based on available data, provided the patient is on a stable antidepressant regimen and receives close clinical monitoring.
One case report has been received of adverse reactions with phentermine and the antidepressant fluoxetine. Major At high doses, yohimbine may nonselectively inhibit MAO and also, at normal doses, activates the sympathetic nervous system. Traditional MAOIs can cause serious adverse effects when taken concomitantly with sympathomimetics. Different formulations of phentermine as a single agent are available under various brand names, in many countries.
Phentermine is used for a short period of time to promote weight loss, if exercise and calorie reduction are not sufficient, and in addition to exercise and calorie reduction. Phentermine is approved for up to 12 weeks of use and most weight loss occurs in the first weeks. Phentermine use is contraindicated in those who: Phentermine may decrease the effect of drugs like clonidine , methyldopa , and guanethidine.
Drugs to treat hypothyroidism may increase the effect of phentermine. Rare cases of pulmonary hypertension and cardiac valvular disease have been reported. There is no evidence that phentermine is safe for women who are pregnant. Other adverse effects include: Phentermine has some similarity in its pharmacodynamics with its parent compound, amphetamine , as they both are TAAR1 agonists ,  where the activation of TAAR1 in monoamine neurons facilitates the efflux or, release into the synapse, of these neurochemicals; at clinically relevant doses, phentermine primarily acts as a releasing agent of norepinephrine in neurons , although, to a lesser extent, it releases dopamine and serotonin into synapses as well.
The primary mechanism of phentermine's action in treating obesity is the reduction of hunger perception, which is a cognitive process mediated primarily through several nuclei within the hypothalamus in particular, the lateral hypothalamic nucleus , arcuate nucleus , and ventromedial nucleus. Outside the brain, phentermine releases norepinephrine and epinephrine — also known as noradrenaline and adrenaline respectively — causing fat cells to break down stored fat as well.
In , phentermine first received approval from the United States FDA as an appetite-suppressing drug. Phentermine was marketed with fenfluramine or dexfenfluramine as a combination appetite suppressant and fat burning agent under the popular name fen-phen. In , after 24 cases of heart valve disease in fen-phen users, fenfluramine and dexfenfluramine were voluntarily taken off the market at the request of the FDA. Phentermine is still available by itself in most countries, including the US.
In contrast, amphetamine preparations are classified as Schedule II controlled substances. Phentermine can be produced from benzaldehyde and 2-nitropropane as follows: From Wikipedia, the free encyclopedia. S4 Prescription only CA: NC Cc1ccccc1 C C. Retrieved 16 November