katherine asked
I have been on phentermine 30 mg for 2 months by my primary doctor, I took my last dose around 9 am yesterday morning. I have degenerative disc disease and have a tremendous amount of pain. I went to see my back doctor and he prescribed me tramadol. I looked up Tramadol and it has an interaction with phentermine. This is the first time I have seen my back doctor in 3 months and I completely blanked on updating him about the phentermine I was prescribed. When will it be safe to take the Tramadol? I do not want to mix them or have any kind of reaction!
At a glance
- There is a potential interaction between phentermine and tramadol. They shouldn't be used together unless directed by your doctor. Taking both could potentiall increase the risk of seizures and serotonin syndrome.
Answer
You are correct that there may be a potential interaction between tramadol and phentermine, but just how severe or prevalent it is, isn't well known.
There is actually quite a discrepancy regarding just what the interaction is between tramadol and phentermine. For example, three different online resources for drug interactions have three different interactions listed!
- Drugs.com lists a 'major' interaction, citing an increased risk of seizures.
- RxList.com states there is an interaction based on their opposing sedative and stimulating effects.
- Rxisk.org lists an interaction based on an increased risk of serotonin syndrome.
Clearly, there is something off if three different (and reputable) drug interaction checkers are listing unique adverse reactions.
After doing a little research, all of the interactions listed by the online tools are based on the known characteristics of each drug, and not so much based on published reports or studies. In other words, they are more theoretical than anything.
Tramadol - Phentermine Interactions
Studies or case reports specifically linking tramadol and phentermine to the listed interactions are practically non-existent. Nevertheless, I discuss these three potential interactions (seizures, opposing effects, serotonin syndrome) below.
Increased Risk Of Seizures
Tramadol (brand name Ultram) has been associated with an increased risk of seizures. The prescribing information for the drug explicitly warns against its concurrent use with other drugs that may cause seizures:
References
- Elsevier ClinicalKey: Phentermine Monograph (Accessed 2/13/19)
- Elsevier ClinicalKey: Tramadol Monograph (Accessed 2/13/19)
- Elsevier ClinicalKey: Amphetamine salts Monograph (Accessed 2/13/19)
- Drugs Implicated In Seizures and Its Management. Journal of Pharmacology and Clinical Research
- Adipex-P Prescribing Information
- Off-label drugs for weight management. PubMed
- Fenfluramine-Phentermine (Fen-Phen) and Seizures: Evidence for an Association. PubMed
- Tramadol Seizures, Serotonin Syndrome, and Coadministered Antidepressants. PubMed
- Ultram Package Insert
