From the Guidelines
Metformin does not have a well-documented association with causing pruritus as a common side effect. The most recent and highest quality study, 1, discusses the pharmacologic approaches to glycemic treatment, including the use of metformin as a first-line treatment for type 2 diabetes, and highlights its effectiveness and safety. The study mentions the principal side effects of metformin, which include gastrointestinal intolerance due to bloating, abdominal discomfort, and diarrhea, but does not mention pruritus as a common side effect.
When considering the potential side effects of metformin, it is essential to prioritize the most recent and reliable evidence. In this case, the study 1 provides a comprehensive overview of metformin's benefits and risks, emphasizing its role in reducing microvascular complications, cardiovascular events, and death. While pruritus may occur in some patients, it is not a well-documented or common side effect of metformin, and other factors should be considered when evaluating itching or skin reactions in patients taking this medication.
Key points to consider when evaluating the side effects of metformin include:
- Gastrointestinal intolerance is a common side effect, which can be mitigated by gradual dose titration and/or using extended-release formulations
- Metformin is cleared by kidney filtration and may be safely used in people with estimated glomerular filtration rate ≥30 mL/min/1.73 m²
- Very high circulating levels of metformin have been associated with lactic acidosis, although this complication is very rare
- Metformin use is also associated with increased risk of vitamin B12 deficiency and worsening of symptoms of neuropathy
In clinical practice, if a patient experiences itching while taking metformin, it is crucial to consult with a healthcare provider to evaluate for other causes of itching and consider alternative diabetes medications if necessary. However, based on the current evidence, pruritus is not a well-established side effect of metformin, and its use should be guided by the most recent and reliable clinical guidelines, such as those outlined in the study 1.
From the Research
Metformin and Pruritus
- Metformin has been associated with various cutaneous side-effects, including leukocytoclastic vasculitis, bullous pemphigoid, psoriasiform drug eruption, lichen planus, and acute alopecia 2.
- A case report described a patient who developed DRESS syndrome, characterized by a rash, generalized pruritus, lymphadenopathy, and eosinophilia, after metformin treatment 3.
- Another case report described a patient with metformin-induced generalized bullous fixed-drug eruption, which presented with generalized bullous lesions and pruritus 4.
- A systematic review and meta-analysis of different metformin formulations found that metformin is associated with a high incidence of gastrointestinal side effects, but did not specifically mention pruritus as a common side effect 5.
- However, the review of metformin in dermatology did not mention pruritus as a common side effect of metformin use 2, 6.
Cutaneous Side-Effects of Metformin
- Cutaneous side-effects associated with metformin use include: + Leukocytoclastic vasculitis + Bullous pemphigoid + Psoriasiform drug eruption + Lichen planus + Acute alopecia + DRESS syndrome + Generalized bullous fixed-drug eruption
- These side-effects are rare and may require discontinuation of metformin treatment 2, 3, 4.
Clinical Implications
- Clinicians should be aware of the potential cutaneous side-effects of metformin, including pruritus, and monitor patients for these adverse reactions 3, 4.
- If a patient develops pruritus or other cutaneous side-effects while taking metformin, the medication should be discontinued and alternative treatments considered 3, 4.