Potential issues with antibiotic treatment

Side effects from antibiotic treatment may contribute to non-adherence to therapy, potentially leading to treatment failure. Antibiotic failure may also be due antimicrobial resistance.

Side effects

Nitrofurantoin has been linked to side effects affecting the lungs and liver.^10,11 Patients need to be vigilant for:

• New or worsening respiratory symptoms while taking nitrofurantoin. Symptoms such as breathing difficulties, shortness of breath, a lingering cough, coughing up blood or mucus, or pain or discomfort when breathing should be investigated promptly
• Symptoms and signs of liver dysfunction. These may occur in patients taking nitrofurantoin for any duration, but particularly with long-term use. Yellowing of the skin or eyes, upper right abdominal pain, dark urine and pale or grey-coloured stools, itching or joint pain and swelling should be investigated.

Other common side effects include nausea, vomiting, diarrhoea, loss of appetite, headaches and dizziness or feeling sleepy. Serious side effects may include blood problems presenting as unexplained bruising or bleeding, and a severe allergic reaction.¹²

Trimethoprim commonly causes skin reactions, such as itching or a rash, diarrhoea, nausea or vomiting, headaches, electrolyte imbalance and fungal overgrowth.^11,13 Serious side effects are rare, but may include blood problems, a serious allergic reaction or diarrhoea containing blood or mucus, or lasting longer than 4 days.¹³

Antimicrobial resistance

When people have had several UTIs, and several courses of antibiotics to treat these infections, antibiotics may initially appear to work with symptoms resolving for a while. However, the more resistant organisms are known to attach themselves to the bladder wall and form colonies of resistant bacteria within other parts of the body, such as the kidneys. These colonies of resistant bacteria can multiply over time and become immune to the effect of the antibiotics. They become harder to eradicate, even when taking powerful antibiotics.¹⁴

Some E.coli strains produce an enzyme called extended-spectrum beta-lactamases (ESBL). The resulting ESBL-producing E. coli strains are resistant to trimethoprim, although nitrofurantoin remains effective.¹⁵ Another cause of antibiotic resistant UTIs is ESBL-producing Klebsiella pneumoniae.¹⁴ The prevalence of ESBL-producing E. coli and K. Pneumoniae is increasing worldwide.¹⁶ Resistant bacteria continue to multiply and spread, leading to an antibiotic resistant UTI that can become chronic. This can also lead to more severe infections such as pyelonephritis, and potentially result in serious complications like sepsis.^14,16

This is why antimicrobial stewardship is so important.