How Long To Wait Before Sun Exposure After Taking Bactrim
In our latest question and answer, the pharmacist discusses how long you need to wait after taking Bactrim (sulfamethoxazole/trimethoprim) to go in the sun.
How many days after finishing Bactrim do I need to wait before sun exposure?
Jun 19, 2022- Bactrim can make your skin more sensitive to the sun, causing an exaggerated sunburn reaction that can happen within minutes of sun exposure. It takes about three days for Bactrim to be completely eliminated from your body, so you should avoid direct sunlight during this time. If you must be in the sun while taking Bactrim, use broad-spectrum sunscreen with at least 15 SPF and wear protective clothing like long sleeves, pants, a hat, and sunglasses.
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Overview
Bactrim, also known as co-trimoxazole, is a combination antibiotic, consisting of sulfamethoxazole and trimethoprim, that is used to treat a variety of bacterial infections.
Bactrim, like many other drugs, can increase an individual's sensitivity to the sun.
This sensitivity to sun exposure is actually considered a phototoxic reaction, where the drug (Bactrim in this case) absorbs UVA light and causes cellular damage.
This reaction can occur when exposed to sufficient amounts of and is often characterized as an exaggerated sunburn.
This reaction can occur within minutes after the sun exposure. In most cases, the affected areas are only those that are directly exposed to sunlight.
The best way to avoid this reaction from happening is to avoid prolonged sun exposure while taking the drug or using a broad-spectrum sunscreen.
How Long To Wait
In terms of how long to avoid direct sun, you have to consider how long it takes for Bactrim to be metabolized and removed from your system.
The half-life of a drug is a good way to estimate how long it takes for it to be eliminated (the half-life of Bactrim is between 8–10 hours).
It takes 5 to 6 half-lives, in general, to eliminate a drug from your system. Therefore, the Bactrim should be eliminated from your system after about three days.
To ensure that you do not have a phototoxic reaction to the sun, you should wait 3 days until direct sunlight exposure to be completely safe. At the very least, remember to practice safe sun protection any time you are in the sun.
It is recommended by the CDC to use a sunscreen 15 SPF or higher anytime you are in the sun to reduce the risk of skin cancer and reapply after 2 hours.
If you are going to be in the sun for a long period of time, attempt to cover up as much as possible with long sleeves and pants, wear a hat, and protect your eyes from cataracts with sunglasses.
Final Words
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References & sources
Glossary — Terms in This Answer
- Co-trimoxazole
- The medical name for the antibiotic combination drug commonly known as Bactrim.
- Sulfamethoxazole
- One of two antibacterial medications that are combined together in Bactrim.
- Trimethoprim
- The second antibacterial medication combined with sulfamethoxazole in Bactrim.
- Phototoxic reaction
- A harmful skin reaction caused when a drug in your body absorbs ultraviolet light and damages your cells.
- UVA light
- A type of ultraviolet radiation from the sun that can penetrate deep into the skin.
- Half-life
- The amount of time it takes for half of a drug dose to be broken down and removed from your body.
- Metabolized
- The process by which your body breaks down a drug into substances it can eliminate.
- Broad-spectrum sunscreen
- A sunscreen that protects against both UVA and UVB types of ultraviolet radiation.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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