What are the side effects of Gemtesa (vibegron)?

Side Effects of Gemtesa (Vibegron)

Gemtesa (vibegron) has a favorable side effect profile compared to antimuscarinic medications, with the most common adverse reactions being headache, nasopharyngitis, diarrhea, nausea, and upper respiratory tract infection.

Common Side Effects

Gemtesa's FDA-approved label reports the following common adverse reactions (occurring in ≥2% of patients and at rates higher than placebo):

• Headache (4.0% vs 2.4% for placebo) 1
• Nasopharyngitis (2.8% vs 1.7% for placebo) 1
• Diarrhea (2.2% vs 1.1% for placebo) 1
• Nausea (2.2% vs 1.1% for placebo) 1
• Upper respiratory tract infection (2.0% vs 0.7% for placebo) 1
• Urinary tract infection (reported in 6.6% of patients in long-term studies) 1

Less Common Side Effects

Other adverse reactions reported in <2% of patients treated with Gemtesa include:

• Gastrointestinal disorders: dry mouth, constipation 1
• Investigations: increased residual urine volume 1
• Renal and urinary disorders: urinary retention 1
• Vascular disorders: hot flush 1

Long-Term Safety Profile

In long-term extension studies (up to 52 weeks):

• The safety profile remained consistent with the 12-week studies 2
• Most common adverse events included hypertension (8.8%), urinary tract infection (6.6%), headache (5.5%), and nasopharyngitis (4.8%) 2
• Dry mouth was notably less common with vibegron (1.8%) compared to antimuscarinic medications like tolterodine (5.2%) 2
• Discontinuation rates due to adverse events were low at 2.4% 2

Post-Marketing Experience

The following adverse reactions have been identified during post-approval use of vibegron:

• Urologic disorders: urinary retention 1
• Skin and subcutaneous tissue disorders: angioedema of the face and larynx; hypersensitivity reactions including urticaria, pruritus, rash and drug eruption; eczema 1
• Gastrointestinal disorders: constipation 1

Comparison to Other OAB Medications

Advantages Over Antimuscarinic Drugs

• Significantly lower incidence of dry mouth, constipation, and blurred vision compared to antimuscarinic medications 3
• Lower discontinuation rates due to adverse effects 4
• Antimuscarinic medications (like fesoterodine, solifenacin, tolterodine, and trospium) have higher rates of adverse effects than placebo, with number needed to harm ranging from 6-12 3

Comparison to Other β3-Adrenergic Agonists

• Similar safety profile to mirabegron (another β3-adrenergic agonist) 4
• Both vibegron and mirabegron have reported hypertension as a common adverse event (8.8-9.2%) 4
• Vibegron has fewer drug interactions due to lack of CYP enzyme interactions 5

Special Populations and Considerations

Drug Interactions

• Increases digoxin concentrations - serum digoxin levels should be monitored when starting, during, or discontinuing Gemtesa 1
• Unlike mirabegron, vibegron does not interact with cytochrome P450 enzymes, making it advantageous for patients on multiple medications 5

Elderly Patients

• Sub-analyses of patients ≥65 years have shown continued efficacy and safety 5
• The favorable drug interaction profile is particularly beneficial for older patients with polypharmacy 5

Monitoring Recommendations

• For patients taking digoxin: monitor serum digoxin concentrations before initiating and during therapy with Gemtesa 1
• For patients with urinary retention risk: monitor for signs of urinary retention, especially in those with bladder outlet obstruction 1
• For patients with hypertension: consider monitoring blood pressure, as hypertension has been reported in long-term studies 2, 4

Patient Counseling

• Advise patients that Gemtesa tablets can be swallowed whole with water or crushed and mixed with applesauce 1
• Inform patients about the potential for angioedema and to seek immediate medical attention if experiencing swelling of the face, lips, tongue, or throat 1
• Educate patients about the possibility of urinary retention and to report inability to empty the bladder 1

Gemtesa represents a valuable addition to overactive bladder treatment options with a favorable side effect profile compared to antimuscarinic medications, particularly regarding dry mouth and constipation, which are common reasons for treatment discontinuation.