Phentermine During Pregnancy – Is it Safe to Take?

Most women of child bearing age (17-64) use these medications for weight loss management.Phentermine can produce clinically significant weight loss in women with obesity during the preconception period (2).Even though very efficient in aiding weight loss, Phentermine has major concerns due its adverse effects and its usage in pregnancy.

Is It Safe to Take Phentermine During Pregnancy?

Phentermine use in pregnancy is inadvertent and is considered harmful. The number of women of child bearing age with obesity go for the weight loss process to increase the chances of pregnancy, it in turn increases the exposure of drugs like Phentermine which is used to reduce weight. Most women may get pregnant while using Phentermine. Even though the use of drugs is not intentional there may be potential risks if women get exposed to Phentermine during pregnancy or conceive while using it as many of the birth defects start forming at the early stage of pregnancy.

Phentermine is placed at Pregnancy category X by USFDA demonstrating fetal abnormalities and evidence of human fetal risk if used during pregnancy. There is strict indication that category X drugs should not be taken in pregnancy. Phentermine is highly contraindicated in pregnancy and should not be taken at any stage of pregnancy in any form.

Is There Any Risk to Mothers on Taking Phentermine During Pregnancy?

Most of the studies were against taking Phentermine during pregnancy as it involves various risks at any stage. As excessive weight loss during pregnancy is not safe even for women who are obese while becoming pregnant. The indication is always not to gain more weight and implement a healthy active lifestyle with a balanced diet and appropriate exercise so that the weight gain is minimal if the pregnant woman is obese. All anti obesity drugs are not recommended during pregnancy.

Most significant risk of using Phentermine while pregnant is studies show the increase in risk of gestational diabetes during pregnancy (3) and also diabetes in later stages of life. There may be difficulties during labor as the weight of the babies is higher and has bigger head circumference due to exposure to Phentermine(3a) and delay in delivery might invite other problems such as high blood pressure and pre eclampsia.

Does Taking Phentermine During Pregnancy Cause Any Birth Defects?

There are only minimal studies done on Phentermine usage during Pregnancy. Out of them a study done on exposure of Phentermine during the first trimester has concluded that there is no increased risk of major or minor birth defects observed in the offspring born to women who had taken Phentermine in recommended doses during first trimester exposure (3b). In contrast to that a study had shown a correlation between phentermine exposure during pregnancy and fetal stroke. The study done reported there may be increased chances of fetal stroke if pregnant women get exposed to phentermine during first and second trimester of pregnancy (1). 

A recent study revealed that using certain anti-obesity drugs like Phentermine during pregnancy causes larger than gestational age infants and newborns with higher birth weight. They also correlate the use of Phentermine in pregnancy with abnormal mitral valve development in heart and brain cysts in infants even though no straight correlation might increase these effects. The most usual combination for weight loss is Phentermine and topiramate. Few studies infer that using this combination during pregnancy or exposure to this combination while becoming pregnant may lead to cleft lip a birth defect in babies (4).

Side Effects of Taking Phentermine During Pregnancy

Phentermine comes with some undesirable side effects. Some of them may cause serious side effects as well. Women taking Phentermine might experience some of these adverse side effects and it is advised to consult the doctor if you experience any of these (5)

• Sudden vision disturbances
• Palpitations- hearing their own heart beat
• Eye pain or redness
• Shortness of breath
• Blisters on skin
• Blood in urine
• Severe back pain
• Fast or shallow breathing

Some of the few common side effects include :-

• Difficulty in urination
• Dry mouth and unusual thirst
• Painful menstrual periods
• Nausea, diarrhea, constipation.
• Painful menstrual cramps
• Muscle tightness
• Decreased sense of touch or ability to feel sensation etc.

There are many other side effects that can be experienced. Few are tolerated but some side effects require medical attention.

Does Phentermine Cause Withdrawal Symptoms?

Phentermine does not cause any withdrawal symptoms, Phentermine abuse or psychological dependence or addiction. No withdrawal symptoms will be experienced on cessation of treatment abruptly even at doses much higher than commonly recommended. Other than an increase in hunger no serious withdrawal symptoms might occur.

If you are breastfeeding it is not advised to take phentermine as you may pass it to the baby.
Most of the studies were not mentioned to know its proper effects. Stimulants like phentermine can pass through breast milk and cause potential risks for babies too.

Questions to Ask Your Consulting Physician Before Using Phentermine

If you are obese and trying to get pregnant and on weight loss medication such as Phentermine Please ask for the following information:-

1. How Long should I need to take this medication
2. Any side effects or withdrawal effects
3. How long should I not plan for pregnancy while taking phentermine
4. What should I do if I get pregnant while using Phentermine and how do I reduce the risk of possible birth defects?
5. Other healthiest options for weight loss management during pregnancy?
6. Any other safe alternatives to Phentermine during the preconception period?

Phentermine medication is used for weight loss by suppressing the appetite and gives a feeling of fullness even for small meals. Most of the women with obesity and finding it difficult to conceive may be prescribed Phentermine by doctors. It’s better not to plan pregnancy while taking Phentermine. Even if you get pregnant unintentionally and have exposure to Phentermine during pregnancy stop taking the medication and consult your doctor immediately.

Phentermine alone and in combination with topiramate might increase the risk of birth defects in newborn and increase the chances of gestational diabetes in women. Few studies have also observed an increase in weight in babies larger than for their gestational age making it difficult for women to deliver and may lead to related complications. Overall Phentermine use is strictly contraindicated during pregnancy at any stage and it’s highly recommended not to take it during and after gestation till you stop breast feeding.Please do consult the doctor before taking these medications.

FAQ’s

1.Is It Safe to Take Phentermine For a Month?

You can take phentermine for less than 12 weeks but not more than that as per USFDA recommendations. It is safe to take for one month , but if you find you are pregnant while taking phentermine please consult the doctor and take his advice on how to stop the medication.

2. How Many Days Does Phentermine Stay in Your System?

Phentermine approximately stays about 4 days in your system once taken. Half of the drug goes out after 20 hrs and the rest of the drug gets eliminated afterwards.

References –

1. Phentermine Use During First and Second Trimesters Associated with Fetal Stroke
   [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6913971/]

2. A Retrospective Study Examining Phentermine on Preconception Weight Loss and Pregnancy Outcomes
   [https://www.sciencedirect.com/science/article/abs/pii/S1530891X20482278]

3. Pregnancy outcomes after first trimester exposure to phentermine/fenfluramine
   [https://pubmed.ncbi.nlm.nih.gov/11877776/]

4. Phentermine/Topiramate
   [https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/phentermine-topiramate]

5. Phentermine and Topiramate
   [https://medlineplus.gov/druginfo/meds/a612037.html]