Subsys and Drowsiness - a phase IV clinical study of FDA data

Summary:

Drowsiness is reported as a side effect among people who take Subsys (fentanyl), especially for people who are female, 50-59 old, have been taking the drug for < 1 month also take Oxycodone, and have Breakthrough pain.

The phase IV clinical study analyzes which people have Drowsiness when taking Subsys. It is created by eHealthMe based on reports of 9,232 people who have side effects when taking Subsys from the FDA, and is updated regularly.

What is Subsys?

Subsys has active ingredients of fentanyl. eHealthMe is studying from 9,239 Subsys users. Check the latest studies of Subsys.

What is Drowsiness?

Drowsiness is found to be associated with 2,871 drugs and 4,770 conditions by eHealthMe. Check the latest studies of Drowsiness.

On Dec, 29, 2025

9,232 people reported to have side effects when taking Subsys.
Among them, 38 people (0.41%) have Drowsiness.

Among these 38 people:

How long have people been on Subsys when they have Drowsiness? *

What is the gender of people who have Drowsiness when taking Subsys? *

female: 61.11 %
male: 38.89 %

What is the age of people who have Drowsiness when taking Subsys? *

What are other drugs people take besides Subsys? *

Oxycodone: 5 people, 13.16%
Fentanyl Transdermal System: 4 people, 10.53%
Dilaudid: 3 people, 7.89%
Singulair: 3 people, 7.89%
Lyrica: 2 people, 5.26%
Opana: 2 people, 5.26%
Hydrocodone: 2 people, 5.26%
Xanax: 2 people, 5.26%
Celexa: 1 person, 2.63%
Coenzyme Q10: 1 person, 2.63%

What are other side effects people have besides Drowsiness? *

Fatigue (feeling of tiredness): 5 people, 13.16%
Application Site Pain: 4 people, 10.53%
Drug Intolerance (drug sensitivity): 4 people, 10.53%
Dizziness: 4 people, 10.53%
Nausea (feeling of having an urge to vomit): 4 people, 10.53%
Headache (pain in head): 3 people, 7.89%
Oral Discomfort (pain or irritation in mouth): 3 people, 7.89%
Diarrhea: 3 people, 7.89%
Withdrawal Syndrome (a discontinuation syndrome is a set of symptoms occurred due to discontinuation of substance): 2 people, 5.26%
Feeling Abnormal: 2 people, 5.26%

What are the existing conditions these people have? *

Breakthrough Pain: 26 people, 68.42%
Back Pain: 4 people, 10.53%
Asthma: 2 people, 5.26%
Pain: 2 people, 5.26%
Cancer Pain: 2 people, 5.26%
Gastroesophageal Reflux Disease (a condition in which stomach contents leak backward from the stomach into the oesophagus): 1 person, 2.63%
Brain Neoplasm (tumour of brain): 1 person, 2.63%
Cancer - Throat Or Larynx: 1 person, 2.63%
Depression: 1 person, 2.63%
Diabetes: 1 person, 2.63%

* Approximation only. Some reports may have incomplete information.

Do you take Subsys and have Drowsiness?

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Related studies:

Effectiveness of, long term effects of, and alternative drugs to Subsys:

Subsys (9,239 reports)

Drowsiness treatments and more:

Drowsiness (269,040 reports)

Browse all side effects of Subsys:

a b c d e f g h i j k l m n o p q r s t u v w x y z

Browse all the drugs that are associated with Drowsiness:

Drowsiness (2,871 drugs)

Browse all the conditions that are associated with Drowsiness:

Drowsiness (4,770 conditions)

How the study uses the data?

The study uses data from the FDA. It is based on fentanyl (the active ingredients of Subsys) and Subsys (the brand name). Other drugs that have the same active ingredients (e.g. generic drugs) are not considered. Dosage of drugs is not considered in the study.

How to use the study?

DO NOT STOP MEDICATIONS without first consulting your doctor. If there are any serious or long term adverse effects discovered in the study, discuss the study with your doctor to ensure that proper medication management will be in place if applicable.

Who is eHealthMe?

With medical big data and proven AI/ML algorithms, eHealthMe provides a platform for everyone to run phase IV clinical trials. We study millions of patients and 5,000 more each day. Results of our real-world drug study have been referenced on 800+ peer-reviewed medical publications, including The Lancet, Mayo Clinic Proceedings, and Nature. Our analysis results are available to researchers, health care professionals, patients (testimonials), and software developers (open API).

WARNING, DISCLAIMER, USE FOR PUBLICATION

WARNING: Please DO NOT STOP MEDICATIONS without first consulting a physician since doing so could be hazardous to your health.

DISCLAIMER: All material available on eHealthMe.com is for informational purposes only, and is not a substitute for medical advice, diagnosis, or treatment provided by a qualified healthcare provider. All information is observation-only. Our phase IV clinical studies alone cannot establish cause-effect relationship. Different individuals may respond to medication in different ways. Every effort has been made to ensure that all information is accurate, up-to-date, and complete, but no guarantee is made to that effect. The use of the eHealthMe site and its content is at your own risk.

If you use this eHealthMe study on publication, please acknowledge it with a citation: study title, URL, accessed date.