From the Guidelines
Doxycycline commonly causes gastrointestinal side effects, including nausea, vomiting, diarrhea, and stomach pain, as well as photosensitivity, making sun protection essential while taking it. The most recent and highest quality study, 1, recommends taking doxycycline with food and adequate fluids in the upright position to reduce gastrointestinal side effects. Some patients may experience esophageal irritation or ulceration if the medication isn't taken with sufficient water or if lying down immediately after taking it. Other potential side effects include headache, dizziness, rash, and vaginal yeast infections in women. More serious but rare side effects include severe allergic reactions, increased intracranial pressure, and liver toxicity.
To minimize side effects, it is recommended to:
- Take doxycycline with a full glass of water and food (though not with dairy products, which can reduce absorption)
- Remain upright for at least 30 minutes after taking it
- Use sun protection
- Complete the full prescribed course
These side effects occur because doxycycline, as an antibiotic in the tetracycline class, affects not only harmful bacteria but can also disrupt normal bacterial flora and cellular processes in the body. According to 1 and 1, doxycycline may cause gastrointestinal disturbances, including nausea, vomiting, and diarrhea, as well as esophagitis, phototoxicity, and rarely intracranial hypertension.
Key points to consider when taking doxycycline include:
- Taking the medication with plenty of water, during meals, while sitting or standing to reduce the risk of esophagitis and esophageal ulcerations
- Being aware of the potential for photosensitivity and taking necessary precautions to protect the skin from the sun
- Monitoring for signs of serious side effects, such as severe allergic reactions, increased intracranial pressure, and liver toxicity.
From the FDA Drug Label
Adverse Reactions Due to oral doxycycline’s virtually complete absorption, side effects of the lower bowel, particularly diarrhea, have been infrequent The following adverse reactions have been observed in patients receiving tetracyclines: Gastrointestinal: anorexia, nausea, vomiting, diarrhea, glossitis, dysphagia, enterocolitis, and inflammatory lesions (with monilial overgrowth) in the anogenital region. Hepatotoxicity has been reported rarely. Skin: toxic epidermal necrolysis, Stevens-Johnson syndrome, erythema multiforme, maculopapular and erythematous rashes. Renal toxicity: Rise in BUN has been reported and is apparently dose related. Hypersensitivity reactions: urticaria, angioneurotic edema, anaphylaxis, anaphylactoid purpura, serum sickness, pericarditis, and exacerbation of systemic lupus erythematosus. Blood: Hemolytic anemia, thrombocytopenia, neutropenia, and eosinophilia have been reported. Other: bulging fontanels in infants and intracranial hypertension in adults.
The side effects of doxycycline include:
- Gastrointestinal issues such as anorexia, nausea, vomiting, diarrhea, and hepatotoxicity
- Skin reactions including toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme
- Renal toxicity with a rise in BUN
- Hypersensitivity reactions like urticaria, angioneurotic edema, and anaphylaxis
- Blood disorders including hemolytic anemia, thrombocytopenia, and neutropenia
- Other effects like bulging fontanels in infants and intracranial hypertension in adults 2 Additionally, doxycycline may cause:
- Clostridium difficile associated diarrhea (CDAD), which can range from mild diarrhea to fatal colitis 2
- Photosensitivity manifested by an exaggerated sunburn reaction 2
From the Research
Side Effects of Doxycycline
- Gastrointestinal adverse effects are a known side effect of doxycycline, with esophagitis being the most pronounced among these effects 3.
- The incidence of gastrointestinal adverse effects was significantly higher in patients who were ≥ 50 years than < 50 years old and in those who received a daily dose of 200 mg than 100 mg 3.
- A study found that 12 patients (6.3%) reported having gastrointestinal adverse effects resulting in doxycycline discontinuation in five of them (2.6%), and three patients (1.6%) had esophagitis 3.
- Another study found that the incidence of side effects was highest and compliance was lowest in the doxycycline-metronidazole group, but the difference was not statistically significant 4.
- Doxycycline has been compared to other antibiotics in various studies, but these studies do not provide direct information on the side effects of doxycycline alone 5, 6, 7.