What are the side effects of doxycycline (antibiotic)?

From the Guidelines

Doxycycline is associated with several side effects, including gastrointestinal disturbances, photosensitivity, and esophagitis, which can be mitigated by taking the medication with food and adequate fluids in the upright position. The most common side effects of doxycycline include nausea, vomiting, diarrhea, and stomach pain, which occur in approximately 15.7% of patients compared to 5.9% of those taking a placebo 1. Additionally, doxycycline can cause photosensitivity, making users more prone to sunburns, and esophageal irritation or ulceration if taken without enough water or right before lying down 1. Other potential side effects include headache, dizziness, rash, and yeast infections, particularly vaginal yeast infections in women due to disruption of normal bacterial flora. Rarely, doxycycline can cause more serious effects like severe allergic reactions, liver problems, or a condition called intracranial hypertension (increased pressure in the skull) 1.

• To minimize side effects, it is recommended to take doxycycline with a full glass of water while sitting or standing, and to avoid lying down for at least 1 hour after taking the medication 1.
• Patients should also be counseled on the potential benefits and harms of doxycycline, including the risk of antimicrobial resistance and changes in the microbiome 1.
• It is essential to review the patient's medication list to assess for possible drug interactions, as doxycycline can interact with other medications, including dairy products, antacids, and supplements containing calcium, iron, magnesium, or sodium bicarbonate 1.

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. When given over prolonged periods, tetracyclines have been reported to produce brown-black microscopic discoloration of the thyroid gland. Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including doxycycline, and may range in severity from mild diarrhea to fatal colitis.

The side effects of doxycycline include:

• Gastrointestinal issues such as anorexia, nausea, vomiting, diarrhea, and hepatotoxicity
• Skin reactions like toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme
• Renal toxicity with a rise in BUN
• Hypersensitivity reactions including urticaria, angioneurotic edema, and anaphylaxis
• Blood disorders like hemolytic anemia, thrombocytopenia, and neutropenia
• Other effects such as bulging fontanels in infants, intracranial hypertension in adults, and brown-black microscopic discoloration of the thyroid gland
• Clostridium difficile associated diarrhea (CDAD), which can range from mild to fatal colitis 2 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.
• Doxycycline has been compared to other antibiotics in terms of efficacy and safety, but the evidence is of very low-certainty due to imprecision and methodological quality of the included studies 4.
• Resistance to doxycycline has been reported in various bacterial strains, including Mycoplasma genitalium and Rickettsia tsutsugamushi 5, 6.
• The weighted pooled resistance rates for doxycycline in clinical Vibrio cholerae O1/O139 isolates were found to be 7% 7.

Specific Side Effects

• Esophagitis: 1.6% of patients reported esophagitis in a study of adults who received oral doxycycline for at least one month 3.
• Gastrointestinal adverse effects: 6.3% of patients reported gastrointestinal adverse effects, resulting in discontinuation of doxycycline in 2.6% of patients 3.
• Serious adverse events: the evidence is uncertain due to very low-certainty, but there were no clear differences between doxycycline and other antibiotics in terms of serious adverse events 4.