Obesity is a chronic medical condition and various medications are presently in use to help individuals fight the battle of the bulge. Pharmacotherapy has been known to help patients achieve anywhere between 5% to 15% weight loss from prescription medication in combination with appropriate lifestyle and diet modification. Among the different medications in use, Phentermine is one of the most popular, and has been in use for more than six decades since FDA approval. This article deals with the side effects of Phentermine and will help you take an informed decision about the use and the right procedures to be followed while taking the medication.

Drug overview and side effects of Phentermine

Before we dwell on the side effects of Phentermine it is essential to understand more about the drug and its mechanism of action. Belonging to the category of sympathomimetic amine anorectic agents, Phentermine is a combination drug used for fighting obesity with significant outcomes in short term weight loss. The biggest advantage of the medication, despite its broad categorization as an amphetamine, is the reduced possibility of addiction. It is widely used in combination with topiramate, and the combination relies on a lesser dosing/proportion of phentermine for desired outcomes in weight management.

Mechanism of action and side effects of Phentermine

The medication is a part of weight management therapy that includes lifestyle modification, and calorific restrictions. It is typically prescribed for patients with a BMI that is more than 30 kg/m2. I tis also prescribed for patients who are obese with comorbid conditions – diabetes, hypertension. The type of obesity that responds best for this medication is exogenous obesity, which refers to the condition wherein an individual consumes food that is more than the required level of activity, which in turn results in increased fat storage. Before we look at the side effects of Phentermine it is time to take a detailed look at the mechanism of action of the medication.

The drug works by suppressing appetite, which is attributed to the increased levels of Leptin as a result of the medication. However, there are other properties that are also known to be responsible for weight loss. For instance, weight loss is also attributed to the increase in the amount of energy expended while resting. The drug whenever used as a single drug or as a part of combination therapy has delivered results in around 4 weeks. Additionally, weight management after the regimen has been stopped has also been shown as promising. It works by releasing noradrenaline which in turn triggers the beta2-adrenergic receptors. The drug causes increased levels of norepinephrine, and dopamine and inhibits a pathway that is responsible for triggering feelings of hunger. As a result of the combined processes, including the reduction in the hunger signals in the body, individuals experience significant weight reduction.

Side effects of Phentermine – common warnings about the drug

Among the different side effects of Phentermine, there are certain effects that warrant additional caution. For instance, the drug is known to trigger dependence due to the mechanism of action. Specifically, patients need to inform treating specialists about prior drug abuse, when taking the medication. Phentermine was earlier available in a combination with two other drugs and the medication caused abnormal valves, which resulted in its discontinuation. The present form of the combination medication is relatively harmless, though it is essential to report any abnormal symptoms. For instance, patients who experience abnormal fatigue, general weakness, shortness of breath when indulging in certain routine activities need to report the same to the doctor. Similarly, swelling in the lower limb extremities and a pacy heart beat or pain in the chest require medical attention.

The drug is also known to cause primary pulmonary hypertension. PPH refers to a possible fatal condition wherein the lungs are affected as a result of high blood pressure in the arteries and the right side of the heart. Typical symptoms of the condition include, pacy heartbeat, discoloration of the lips, and unexplained tiredness. Individuals with the condition are also likely to witness swelling in the lower limbs, and a dizzy feeling. These symptoms need to be reported at the earliest for symptomatic management of the condition.

Common side effects of Phentermine

In addition to the above, there are common side effects of Phentermine that may not be serious in nature. For instance, individuals are likely to experience a dry mouth as a result of the medication. There is a likelihood of patients experiencing constipation, while some experience a bad taste in the mouth. Certain patients may end up with a headache, while others may experience sudden vomiting sensation. While most of these effects are mild in nature and do not typically last long, it is necessary to seek medical intervention when the symptoms are persistent, especially when patients have symptoms such as diarrhea.

Drug interactions of the medication

In addition to the side effects of Phentermine it is necessary to learn about the various drug interactions of the medication. As a result of the mechanism of action and the class of drugs to which it belongs, the medication interactions with other OTC and prescription medications, apart from herbal and vitamin supplements. The medications with which Phentermine interact includes – MAOIs, SSRIs and weight loss medications. For instance, individuals on monoamine oxidase inhibitors are advised to take Phentermine only after a gap of two weeks. Similarly, individuals who have taken Phentermine need to have a clear gap of two weeks before taking any MAOI medication. The possible outcome of the drug interaction could be hypertension, wherein there is an adverse increase in blood pressure levels.

Similarly, individuals on SSRIs can also experience an increase in blood pressure levels that could pose a serious risk. It is therefore necessary to ensure that there is a clear gap of fortnight between the two medications. The gap applies to the commencement of either of the medications after the other has been stopped. Other drug interactions include an increase of side effects of Phentermine when taken alongwith other anti-obesity medications. The risks of taking these two medications together include arrhythmia and high blood pressure levels.

Precautions to be taken by individuals with certain conditions

Individuals diagnosed with certain conditions are expected to take certain precautions to avoid side effects of Phentermine. For instance, individuals with primary pulmonary hypertension are advised to stay away from the medication, as Phentermine could aggravate the condition. Individuals with specific heart conditions such as arrhythmia and valve disease are at risk of experiencing a sudden spike in blood pressure levels. Similarly, individuals with coronary heart disease may end up increasing the load on the heart as a result of the drug’s mechanism of action. Consequently, this will aggravate the heart disease and expose the patient to higher risk levels.

Patients with an overactive thyroid are at risk of increasing thyroid levels due to the effects of Phentermine. It is therefore necessary to avoid the medication if hyperthyroidism is diagnosed. Similarly, individuals with glaucoma are expected to inform the treating specialist about the condition as the drug is known to have an adverse effect on vision. Eye pressure, which could result in vision damage.

Other side effects of Phentermine that need to be remembered

Individuals with a history of substance abuse are advised to take counselling and specialist care while on the medication. One among the side effects of Phentermine is the likelihood of habit forming among patients. It is therefore necessary to inform the treating specialist to ensure that the medication is not used for extended periods. Additionally, the drug belongs to the X category of drugs. This makes it unsuitable for use by pregnant women. By extension, women who intend to become pregnant are also advised to stop the medication. Women on birth control medication are advised to choose the right contraceptive pills when on Phentermine.

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