No Significant Drug Interaction Between Kesimpta (Ofatumumab) and Amoxicillin
There is no clinically significant drug interaction between Kesimpta (ofatumumab) and amoxicillin that would affect patient morbidity or mortality.
Mechanism of Action and Metabolism
Kesimpta (ofatumumab) is a fully human anti-CD20 monoclonal antibody that works by targeting B cells through a different binding site than other anti-CD20 antibodies 1. It is not metabolized through the cytochrome P450 enzyme system, which is the primary pathway for many drug interactions.
Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis. It is primarily eliminated through renal excretion rather than hepatic metabolism, with minimal involvement of the cytochrome P450 system.
Evidence Supporting No Significant Interaction
The available evidence does not indicate any direct interaction between ofatumumab and amoxicillin:
Separate elimination pathways: Monoclonal antibodies like ofatumumab are eliminated through proteolytic degradation, while amoxicillin is primarily excreted unchanged in urine.
Clinical guidelines: No warnings about interactions between these medications appear in treatment guidelines for either multiple sclerosis (where ofatumumab is used) or infectious diseases (where amoxicillin is used).
Infusion reactions: While ofatumumab can cause infusion-related reactions in approximately 20% of patients 1, these are not exacerbated by concurrent amoxicillin use.
Clinical Considerations
Infection Risk
- Ofatumumab causes B-cell depletion, which theoretically could impact immune response, but this does not contraindicate antibiotic use.
- In clinical trials, the overall rates of infections in patients treated with ofatumumab were similar to comparison groups (51.6% vs. 52.7%) 1.
Administration Timing
- If concerned about theoretical interactions affecting absorption, medications can be spaced by a few hours, though this is not specifically required 2.
Special Populations
- For elderly patients or those with liver disease, standard dosing of both medications can be used, but more careful monitoring may be warranted 2.
Practical Recommendations
Continue both medications as prescribed: No dose adjustments are necessary when using these medications concurrently.
Monitor for standard side effects of each medication independently:
- For ofatumumab: Infusion-related reactions, infections
- For amoxicillin: Gastrointestinal effects, allergic reactions
Be aware of infection symptoms: Since ofatumumab affects the immune system, monitor for signs of worsening infection despite antibiotic therapy.
Conclusion
The available evidence indicates that ofatumumab (Kesimpta) and amoxicillin can be safely administered concurrently without significant drug interactions that would affect patient outcomes. No specific dose adjustments or additional monitoring beyond standard care are required when using these medications together.