Sibutramine
Sympathomimetics
Thyroid hormones
Tricyclic antidepressants
Phendimetrazine Interactions
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 amphetamine, dexfenfluramine, dextroamphetamine, diethylpropion, ephedrine, fenfluramine, or 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.
Concurrent use of dronabinol, THC with sympathomimetics (e.g., amphetamine, cocaine, or other sympathomimetics) may result in additive hypertension, tachycardia, and possibly cardiotoxicity. In a study of 7 adult males, combinations of cocaine (IV) and smoked marijuana (1 g marijuana cigarette, 0-2.7% delta-9-THC) increased the heart rate above levels seen with either agent alone, with increases plateauing at 50 bpm.
Sibutramine is contraindicated in patients taking other centrally-acting appetite suppressant drugs, including phendimetrazine.
Phendimetrazine has vasopressor effects and can decrease the antihypertensive effect of guanethidine. Phendimetrazine may displace guanethidine from the neuron and antagonize the neuronal blockade caused by guanethidine.
Monoamine oxidase inhibitors (MAOIs), or drugs that possess MAO-inhibiting activity such as furazolidone, linezolid, or procarbazine, can prolong and intensify the cardiac stimulation and vasopressor effects of phendimetrazine. Phenelzine and tranylcypromine appear to produce the greatest risk since these two MAOIs also have intrinsic amphetamine-like activity. In the presence of MAOIs, phendimetrazine and other drugs that cause release of norepinephrine induce severe cardiovascular and cerebrovascular responses. It is unclear if selegiline, an inhibitor of MAO type B, can also predispose to this reaction. Phendimetrazine should not be administered during or within 14 days following the use of MAOIs or drugs with MAO-inhibiting activity.
The pressor response to some sympathomimetics is exaggerated in patients currently receiving tricyclic antidepressants. Concomitant use of tricyclic antidepressants with sympathomimetics, including phendimetrazine, should be avoided whenever possible.
Phendimetrazine is a sympathomimetic agent. Sympathomimetics may increase blood sugar via stimulation of beta2-receptors which leads to increased glycogenolysis. A pharmacodynamic interaction with antidiabetic agents may occur. Patients receiving antidiabetic agents should be closely monitored for loss of diabetic control when therapy with sympathomimetic agents is instituted. Conversely, diabetic patients may have decreased requirements of insulins, sulfonylureas or other antidiabetic agents in association with the use of phendimetrazine and the concomitant dietary regimen and weight loss. As long as blood glucose is carefully monitored to avoid hypoglycemia or hyperglycemia, it appears that phendimetrazine can be used concurrently.
Halogenated anesthetics sensitize the myocardium to the effects of sympathomimetics. Chronic use of sympathomimetics prior to halogenated anesthetics may result in cardiac arrhythmias. Phendimetrazine should be discontinued several days prior to surgery using halogenated anesthetics.
The pharmacologic effects of phendimetrazine are similar to amphetamines. Amphetamines do not relieve cognitive impairment that results from ethanol intoxication, even though subjective improvements in motor performance have been noted on concomitant ingestion by patients. Ethanol containing beverages should generally be avoided while taking psychostimulants.
Caution is advised when using thyroid hormones in combination with phendimetrazine; co-administration of sympathomimetics and thyroid hormones can enhance the cardiovascular effects of both agents. Patients with coronary artery disease have an increased risk of developing coronary insufficiency from either agent. Use of these agents concomitantly may increase this risk even further.
Atomoxetine has been reported to increase blood pressure and heart rate, probably via inhibition of norepinephrine reuptake. Due to an additive pharmacodynamic effect, phendimetrazine and atomoxetine should be used together cautiously, particular in patients with a history of cardiac disease. Consider monitoring heart rate and blood pressure at baseline and regularly throughout treatment if these agents must be used together.
[ Last revised: 3/11/2005 11:22:00 AM ]
Related entries
Syndicate
