Phentermine And Pregnancy: Safety And Side Effects During Pregnancy And Breast-Feeding

Efforts to shed pounds during pregnancy usually go against medical advice. While addressing the risks of obesity during pregnancy is crucial, controlled weight gain is often considered essential for optimal fetal development. As a result, the pursuit of weight loss is detrimental to the well-being of the unborn child. The use of weight-loss drugs such as phentermine increases the risks to both mother and foetus.

The potential risks associated with the use of phentermine during pregnancy far outweigh any purported benefits for weight loss. Studies suggest that expectant mothers who use phentermine increase their susceptibility to various complications. Heart disease, high blood pressure and congenital anomalies have all been linked to phentermine use during pregnancy. While the adverse effects of phentermine in non-pregnant women are well known, the complexities of pregnancy physiology introduce additional pregnancy-specific risks.

The use of phentermine for weight loss during pregnancy is not justified. The postpartum period offers ample opportunity to explore weight management strategies, including the potential use of phentermine or other medications. Prioritising the health of the developing child remains paramount during this critical period of pregnancy.

Navigating Weight Loss During Pregnancy

Trying to lose weight during pregnancy is a complex endeavour that requires the guidance of healthcare professionals. Pregnancy involves complicated changes in the body’s processes, so it is essential to approach weight loss with caution and expert supervision. Attempting to lose weight on your own is strongly discouraged due to the significant risks involved.

Instead, it is essential to seek the help of healthcare professionals such as your doctor or midwife, as well as a dietician or nutritionist specialising in pregnancy. These professionals have the knowledge and expertise to develop a safe and effective weight management plan tailored to your individual needs and circumstances. Working with a multidisciplinary team ensures that weight loss efforts are conducted in a way that prioritises both maternal and fetal health.

What Is Phentermine? A Controlled Substance For Weight Management

Phentermine is classified by the Food and Drug Administration (FDA) as a controlled substance, specifically a Schedule IV drug. Its primary function is to serve as an appetite suppressant and helps manage obesity. Technically classified as a sympathomimetic amine anorectic, phentermine works by reducing appetite, similar to the effects observed with amphetamines, another sympathomimetic agent.

It is often prescribed in combination with another anorectic, topiramate, as the combined formulation significantly enhances the anorectic effect compared with either drug alone. It is important to note, however, that neither phentermine nor topiramate, let alone their combination, should be used during pregnancy because of the risks involved.

Phentermine was first classified as a Schedule IV drug in 1959 because of its demonstrated low potential for addiction and abuse, although it is not completely free of such risks. This controlled status underlines the importance of careful use. It’s important to recognise that the original formulation was not intended for long-term use, but rather as a short-term supplement, typically up to 12 weeks. Targeted at individuals struggling with exogenous obesity – a condition primarily caused by overeating – phentermine serves as a strategic intervention in weight management protocols.

How Does Phentermine Work? The Mechanism Of Action

Phentermine works by triggering the release of noradrenaline from presynaptic vesicles in the lateral hypothalamus of the brain. This action stimulates the production of beta2-adrenergic receptors, resulting in increased levels of norepinephrine and dopamine, while also affecting serotonin levels.

In addition, phentermine is thought to inhibit neuropeptide Y in the brain, a key signalling molecule involved in the regulation of satiety and energy expenditure. The culmination of these effects leads to an increased resting metabolic rate and suppression of appetite.

Although phentermine has demonstrated efficacy as an appetite suppressant, it’s important to highlight its potential dangers, particularly in the context of pregnancy or lactation. Given the delicate cardiovascular dynamics associated with pregnancy, the use of this amphetamine derivative during these periods could pose significant risks.

Can Phentermine Be Taken During Pregnancy?

Phentermine And Pregnancy

With regard to phentermine and its effect on fertility, it is unlikely that its use will significantly affect the chances of conception for people trying to become pregnant. However, if you are trying to conceive, it is strongly recommended that you discontinue use of phentermine to ensure the wellbeing of any potential offspring.

Due to its pharmacological similarities to amphetamine stimulants, phentermine poses a potential risk of irreversible harm to a developing foetus. In addition, the transfer of amphetamines from mother to infant through breast milk raises concerns for breastfeeding mothers, leading to recommendations against the use of phentermine.

The Food and Drug Administration (FDA) strongly discourages the use of phentermine by pregnant or breastfeeding women, citing the minimal need for weight loss during pregnancy. Instead, the focus is on controlling the rate of weight gain, with safer, non-pharmacological methods available to meet maternal and fetal health needs. If pregnancy occurs during the use of phentermine, immediate discontinuation of the drug is recommended.

Exposure to phentermine during the first trimester of pregnancy carries potential risks, although developmental abnormalities are rare, particularly when used in combination with topiramate. However, the combined risks to the cardiovascular system, exacerbated by the physiological demands of pregnancy, emphasise the need to discontinue the use of phentermine (and/or topiramate) during pregnancy. Recognising the maternal role as an incubator, any complications arising in the mother may have a direct impact on the fetus.

In cases where phentermine use coincides with early pregnancy, discontinuation is of paramount importance. The precautionary approach to pharmaceutical weight loss products for pregnant and lactating women is underscored by the potential risks to maternal and fetal health.

What Is The Best Way To Stop Taking Phentermine During Pregnancy?

If you are already on a course of phentermine when you discover you are pregnant, it is imperative that you speak to a health professional immediately about stopping the medication. Given the addictive properties of phentermine, stopping without professional guidance can pose significant challenges and potential health risks. Addiction to phentermine can develop even when the prescribed dosage is strictly adhered to.

Maternal Risks Associated With Phentermine During Pregnancy

Concerns about phentermine don’t focus on its long-term use, but rather on its use during pregnancy or while breastfeeding, especially during the first trimester.

Expectant mothers should be aware of the potential dangers associated with continued use of phentermine during pregnancy, including but not limited to:

  • Likelihood of global developmental delay
  • Possibility of fetal stroke and brain haemorrhages
  • Development of bilateral porencephalic cysts
  • Incidence of neural tube defects that prevent full spinal development (such as spina bifida)
  • Likelihood of premature labour and delivery
  • Potential for cerebral palsy after birth
  • Increased risk of birth defects above normal background risk
  • Increased birth weight and head circumference compared to typical norms
  • Incidence of neural tube defects that prevent full spinal development (such as spina bifida)

Unfortunately, pregnancy-related information on medicine labels is often not comprehensive enough for expectant mothers. As with any medication, it is strongly recommended that pregnant and breastfeeding women prioritise consultation with their healthcare professional.

Phentermine And Its Impact On Breastfeeding

Is there a risk of phentermine being passed to my baby through breastfeeding? Evidence from a study of mothers who used amphetamines recreationally suggests that these substances can pass to infants through breast milk. Although specific studies on the transfer of phentermine through breastfeeding are limited, many experts speculate that it may follow a similar pattern, based on existing evidence.

Breastfeeding while taking phentermine has been associated with a number of adverse effects in both mother and baby, including tremors, restlessness, sleep disturbances and reduced interest in regular breastfeeding in the baby. These effects can significantly disrupt the crucial bonding period between mother and child, which is crucial to their lifelong relationship.

For those who have stopped using phentermine prior to pregnancy, the risk associated with this factor is reduced.

How Long You Should Wait Before Breastfeeding After Using Phentermine

There are few clinical studies on the optimal length of time to wait before breastfeeding after taking phentermine. However, as with any potentially dangerous dietary medication, it is advisable to avoid using it altogether, especially if you are breastfeeding a newborn baby. It’s important to realise that everything you take in, including food, alcohol and phentermine, can potentially affect your nursing baby. However, it is assumed that you stopped taking phentermine before you became pregnant and therefore before you started breastfeeding.

The elimination half-life of phentermine is usually about 19 to 24 hours, during which time 70 to 80 per cent of the drug is metabolized by the liver and excreted via the urinary tract. Theoretically, if phentermine has been discontinued for a period longer than this half-life, the likelihood of it being passed to an infant through breast milk is greatly reduced. However, it’s unlikely that breastfeeding would occur less frequently than every 19-24 hours.

One study on amphetamine use suggests waiting at least 48 hours before breastfeeding, although it focused on recreational amphetamines rather than phentermine specifically. However, given the chemical similarity between phentermine and amphetamines, this recommendation remains relevant.

It is wise to err on the side of caution – complete avoidance of phentermine is advisable whenever possible. If phentermine has been taken, it is recommended to wait at least two days before exposing the baby to it through expressed breast milk.

Additional Side Effects Of Phentermine

Cases of phentermine overdose are extremely rare, but excessive use can lead to potentially dangerous consequences, including withdrawal symptoms if phentermine use is discontinued for any reason.

Expectant mothers are not the only people at risk when using phentermine for weight loss during pregnancy. The adverse effects associated with excessive use of phentermine include:

  • Tremors
  • Restlessness
  • Increased breathing
  • Mild confusion
  • Constipation or diarrhoea
  • Hyperreflexia (extremely fast reflexes)
  • Paresthesia (pins and needles)
  • Dysgeusia (taste disturbance)
  • Dry mouth
  • Hallucinations
  • Panic and anxiety
  • Decreased libido
  • Tiredness
  • Insomnia
  • Mental depression

In addition, cardiovascular side effects may pose a risk, particularly in susceptible individuals:

  • High blood pressure
  • Irregular heartbeat
  • Tachycardia
  • Circulatory collapse
  • Pulmonary hypertension
  • Myocardial infarction

It’s important to recognise that no weight loss drug is without side effects and withdrawal symptoms. Although phentermine has not been withdrawn from the market by the FDA, there are notable differences between pharmaceutical weight loss and natural approaches to managing obesity.

Making a commitment to a nutritious diet, moderate exercise and a mindful lifestyle is a commitment that will ultimately benefit the wellbeing of your future child.

Does Phentermine Pose A Risk To Pregnancy?

Although phentermine is promoted as an effective fat burner, attempting to lose weight during pregnancy is strongly discouraged. The main focus during pregnancy should be on providing the body with optimal support for the growth and development of the baby.

Although obesity during pregnancy can increase the risk of conditions such as high blood pressure and gestational diabetes, health professionals generally advise against active weight loss, particularly through the use of appetite suppressants such as phentermine. Instead, it is generally recommended that any excess weight be addressed before conception.

Trying to lose weight during pregnancy, even in extreme cases, can lead to complications ranging from premature birth to miscarriage. It can also have a negative effect on the health of the mother, possibly leading to disturbances in blood sugar levels and an increased risk of fainting.

There are also additional risks associated with the use of phentermine during pregnancy, including withdrawal symptoms, which can increase discomfort, particularly during pregnancy. To promote a positive pregnancy outcome, it is advisable to avoid using drugs such as phentermine.

It is important to prioritise the wellbeing of both the mother and the unborn baby. The Food and Drug Administration (FDA) stresses the importance of refraining from weight-loss efforts during pregnancy, emphasising that there will be ample opportunity to address weight concerns after delivery. With a new baby on the horizon, focusing on the health and safety of both mother and child should take precedence over concerns about body mass index.


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