Phentermine, Heart Valves and Lung Pressure
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Can phentermine cause heart valve or lung problems?

From FDA labels, public health agencies and published studies · Reviewed

Short answer: Rarely, according to its label. Serious leaky heart valves and primary pulmonary hypertension, a rare and often fatal lung disease, were reported mostly when phentermine was combined with fenfluramine or dexfenfluramine (fen-phen). The Lomaira label says rare cases with phentermine alone have also been reported and a link cannot be ruled out. Phentermine can also raise heart rate and blood pressure.

What the label says

The Lomaira (phentermine) label has two warnings on this (Warnings):

  • Primary pulmonary hypertension (high pressure in the lung arteries) has been reported with phentermine plus fenfluramine or dexfenfluramine. Rare cases have been reported in people who reportedly took phentermine alone, and a link with phentermine alone cannot be ruled out.
  • Serious regurgitant (leaky) heart valve disease, mainly of the mitral, aortic and tricuspid valves, has been reported in otherwise healthy people who took the same combination. The label says the role of phentermine has not been established, the course after stopping is not known, and rare cases with phentermine alone have been reported.

The label lists palpitations, fast heartbeat, raised blood pressure and ischemic events among reported reactions. It has no boxed warning.

Where the fen-phen reports came from

Connolly and colleagues (1997) described 24 women, average age 44, with no prior heart disease, seen about a year after starting fenfluramine with phentermine. Ultrasound showed unusual valve shapes and leaking in all 24, on both sides of the heart. Eight also had newly found pulmonary hypertension, and 5 had needed heart surgery at the time of the report. The authors wrote that the cases raised concern that the combination may be associated with valve disease.

This was a case series of a two-drug combination, not a trial of phentermine alone. See anorectic for the term labels use for appetite suppressants like phentermine.

Symptoms the label asks people to report

The label says the first symptom of pulmonary hypertension is usually shortness of breath. Others include chest pain, fainting and swelling of the lower legs. It asks people to report right away any worsening in how much exercise they can handle. Treatment is stopped in anyone with new, unexplained shortness of breath, chest pain, fainting or leg swelling, and they are checked for pulmonary hypertension.

Who should not take it

Phentermine is contraindicated in people with a history of heart or blood vessel disease, such as coronary artery disease, stroke, irregular heartbeat, heart failure or uncontrolled high blood pressure, and during or within 14 days of an MAOI antidepressant (Contraindications). The label asks for caution with even mild high blood pressure.

Blood pressure and heart rate readings before and during treatment, along with any new breathlessness, are the details a prescriber will ask about. Dose Track can log the dose with notes and readings in one place.

Read more on Dose Track: Lomaira side effects · Phentermine · Anorectic · Diethylpropion vs phentermine

General education drawn from labels, public health agencies and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your medicine are the final word. Questions for other users? Ask in the Dose Track community.
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Frequently asked questions

Is phentermine the same as fen-phen?+
No. Fen-phen was phentermine taken with fenfluramine or dexfenfluramine. Most valve and lung reports in the label involve that combination.
Can phentermine alone cause heart valve problems?+
The label says rare cases have been reported with phentermine alone and a link cannot be ruled out, but its role has not been established.
What symptoms should be reported on phentermine?+
The label lists new shortness of breath, chest pain, fainting, leg swelling and any drop in exercise tolerance.
Does phentermine raise blood pressure?+
Yes. The label lists raised blood pressure among reactions and asks for caution even with mild high blood pressure.

Sources

  1. Lomaira (phentermine hydrochloride) 8 mg tablets US prescribing information, DailyMed
  2. Connolly et al. N Engl J Med 1997 (valvular heart disease associated with fenfluramine-phentermine). PMID 9271479

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