Metformin (Metformin Hydrochloride) - Side Effects and Adverse Reactions

ADVERSE REACTIONS

In a U.S. double-blind clinical study of metformin in patients with type 2 diabetes, a total of 141 patients received metformin therapy (up to 2550 mg per day) and 145 patients received placebo. Adverse reactions reported in greater than 5% of the metformin patients, and that were more common in metformin- than placebo-treated patients, are listed in Table 7.

Table 7. Most Common Adverse Reactions (>5%) in a Placebo-Controlled Clinical Study of Metformin Monotherapy* 

Adverse Reaction	Metformin Monotherapy (n=141)	Placebo (n=145)
	% of patients
* Reactions that were more common in metformin- than placebo-treated patients.
Diarrhea	53.2	11.7
Nausea/Vomiting	25.5	8.3
Flatulence	12.1	5.5
Asthenia	9.2	5.5
Indigestion	7.1	4.1
Abdominal Discomfort	6.4	4.8
Headache	5.7	4.8

Diarrhea led to discontinuation of study medication in 6% of patients treated with metformin. Additionally, the following adverse reactions were reported in ≥1 to ≤5% of metformin patients and were more commonly reported with metformin than placebo: abnormal stools, hypoglycemia, myalgia, lightheaded, dyspnea, nail disorder, rash, sweating increased, taste disorder, chest discomfort, chills, flu syndrome, flushing, palpitation.

Pediatric Patients

In clinical trials with metformin in pediatric patients with type 2 diabetes, the profile of adverse reactions was similar to that observed in adults.

REPORTS OF SUSPECTED METFORMIN SIDE EFFECTS / ADVERSE REACTIONS

Possible Metformin side effects / adverse reactions in 69 year old male

Reported by a physician from United Kingdom on 2011-10-27

Patient: 69 year old male

Reactions: Skin Discolouration, Skin Lesion, Rash Erythematous, Rash Macular, Naevus Flammeus

Suspect drug(s):
Metformin
    Indication: Type 2 Diabetes Mellitus

Ramipril
    Indication: Type 2 Diabetes Mellitus

Zocor
    Administration route: Oral
    Indication: Hypercholesterolaemia

Aspirin
    Indication: Type 2 Diabetes Mellitus

Possible Metformin side effects / adverse reactions in 50 year old male

Reported by a health professional (non-physician/pharmacist) from United States on 2011-10-28

Patient: 50 year old male

Reactions: Drug Level Increased, Intentional Overdose, Urine Output Decreased, Hypotension, Mental Status Changes, Lactic Acidosis, Toxicity TO Various Agents, Suicide Attempt, Anuria, Renal Failure Acute

Adverse event resulted in: hospitalization

Suspect drug(s):
Metformin HCL
    Dosage: 500 mg, bid
    Indication: Type 2 Diabetes Mellitus

Metformin
    Dosage: 52 g, unk

Possible Metformin side effects / adverse reactions in 66 year old male

Reported by a physician from Germany on 2011-11-08

Patient: 66 year old male weighing 160.0 kg (352.0 pounds)

Reactions: Bile Duct Cancer

Adverse event resulted in: death

Suspect drug(s):
Januvia
    Administration route: Oral
    Indication: Type 2 Diabetes Mellitus
    Start date: 2010-10-01
    End date: 2011-09-01

Metformin
    Administration route: Oral
    Indication: Type 2 Diabetes Mellitus
    Start date: 2009-05-01
    End date: 2011-09-01