Cystitis Medicines UK: Nitrofurantoin and Trimethoprim Explained
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The two prescription antibiotics recommended by NICE for uncomplicated cystitis in the UK are nitrofurantoin (first-line: 100mg modified-release twice daily for 3–5 days, taken with food) and trimethoprim (second-line: 200mg twice daily for 7 days). Both are prescription-only — available via a GPhC-regulated online consultation at Access Doctor without a GP appointment, with next-day delivery.
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Treat Cystitis Online →Nitrofurantoin for Cystitis
Nitrofurantoin is the NICE first-line recommendation for uncomplicated cystitis in women, provided kidney function is adequate (eGFR ≥45 ml/min). It works by stopping harmful bacteria from multiplying — specifically by interfering with bacterial energy metabolism and DNA synthesis. Crucially, nitrofurantoin is rapidly concentrated in the urine at the site of infection in the bladder.
- NICE first-line for uncomplicated UTI/cystitis
- Standard dose: 100mg modified-release twice daily for 3–5 days
- Take with food — significantly reduces stomach upset
- May turn urine dark yellow or brown — normal, temporary, nothing to worry about
- Also sold as Macrobid and Macrodantin
- Does not contain penicillin — safe for those with penicillin allergy
Who Cannot Take Nitrofurantoin?
- Those with known allergy to nitrofurantoin
- Those with severe kidney disease (eGFR <45 ml/min)
- Those with porphyria or G6PD deficiency
- Pregnant women at term (38+ weeks)
- Those with anaemia or vitamin B deficiency
Trimethoprim for Cystitis
Trimethoprim is NICE second-line for cystitis — recommended as an alternative to nitrofurantoin where the first-line option is not appropriate, and where local resistance rates are considered low. It was historically the first-choice UTI antibiotic in the UK, but increasing antibiotic resistance has shifted prescribing practice.
Trimethoprim remains effective for approximately 90% of UTI cases. For full information on dosage, drug interactions, and safety, see: Trimethoprim Tablets for UTI UK. For side effects in detail, see: Trimethoprim Side Effects UK.
- NICE second-line for UTI/cystitis (alternative to nitrofurantoin)
- Standard dose: 200mg twice daily for 7 days
- Does not contain penicillin — safe for penicillin-allergic patients
- Avoid in first trimester of pregnancy (interferes with folate metabolism)
Who Cannot Take Trimethoprim?
- Those allergic to trimethoprim
- Those with liver or kidney problems
- Those with anaemia, low folic acid, porphyria, or blood disorders
- Pregnant women — especially first trimester
Antibiotic resistance reminder: Completing the full prescribed course — even if symptoms resolve early — is vital. Stopping midway significantly increases the risk of the infection returning and of developing antibiotic resistance.
How Long Do Cystitis Antibiotics Take to Work?
Most women notice significant symptom improvement within 24–48 hours of starting the correct antibiotic. Symptoms should fully resolve by the end of the course (3–7 days depending on the antibiotic and dose prescribed).
If you are not feeling better after 48–72 hours, contact your prescriber. This may indicate antibiotic resistance, a misidentified organism, or a need for urine culture before prescribing. Do not take a second course of the same antibiotic without clinical review.
Antibiotic Resistance in UTIs: Why NICE Changed Its Guidance
The shift from trimethoprim to nitrofurantoin as NICE first-line for cystitis reflects a real and growing problem: trimethoprim resistance has been increasing in the UK for several decades. UKHSA surveillance data shows that a significant proportion of E. coli isolates from UTIs are now resistant to trimethoprim in many parts of the UK.
Nitrofurantoin has maintained lower resistance rates because its mechanism of action is less susceptible to the resistance mechanisms that affect trimethoprim. NICE updated its guidance to reflect this. Key principles of antibiotic stewardship:
- Only take antibiotics when prescribed for a confirmed or strongly suspected bacterial infection
- Always complete the full prescribed course
- Never use leftover antibiotics from a previous course
- Never share antibiotic prescriptions
- Report side effects via the MHRA Yellow Card scheme
Over-the-Counter Options
There are no over-the-counter antibiotics for cystitis in the UK — nitrofurantoin and trimethoprim are prescription-only. However, several OTC products can help manage symptoms:
- Paracetamol or ibuprofen — for pain and discomfort relief
- Urinary alkalinising sachets (e.g. Cystopurin, sodium citrate products) — may temporarily ease burning by reducing urine acidity
- Cranberry products — some evidence for prevention; limited evidence for treating active infections
How to Get Cystitis Treatment
If symptoms have persisted for more than 24 hours, seek medical advice. Access Doctor is a GPhC-registered online pharmacy — complete a short consultation reviewed by our GPhC-registered pharmacist independent prescribers. For a full explanation of the online prescribing process, see: UTI Antibiotics Online UK for Women.
💊 NICE First-Line Antibiotic
Nitrofurantoin (Macrobid)
MHRA-approved first-line antibiotic for cystitis & UTIs. Prescription via GPhC-regulated online consultation.
Order Nitrofurantoin →💊 Prescription Antibiotic
Trimethoprim
MHRA-approved alternative antibiotic for cystitis. Suitable where nitrofurantoin is not appropriate.
Order Trimethoprim →Order Cystitis Antibiotics Online
Our GPhC-registered pharmacist independent prescribers review your consultation and prescribe nitrofurantoin or trimethoprim — with next-day discreet delivery.
Treat Cystitis Online →For a comprehensive overview of cystitis and UTI — causes, symptoms, diagnosis and all treatment options — see our complete cystitis and UTI guide. [Pillar page — link to be activated on publication]
Frequently Asked Questions
What is the NICE first-line antibiotic for cystitis?
NICE recommends nitrofurantoin as the first-line antibiotic for uncomplicated cystitis in women, provided kidney function is adequate (eGFR ≥45 ml/min). The standard dose is 100mg modified-release twice daily for 3–5 days, taken with food. Trimethoprim 200mg twice daily for 7 days is the recommended alternative.
Can I get cystitis antibiotics over the counter in the UK?
No — nitrofurantoin and trimethoprim are prescription-only medicines in the UK and cannot be purchased without a prescription. However, you do not need a GP appointment: Access Doctor’s GPhC-registered pharmacist independent prescribers can assess your suitability online and prescribe the appropriate antibiotic with next-day delivery.
Will cystitis antibiotics affect my contraceptive pill?
Current evidence does not support a significant interaction between commonly prescribed UTI antibiotics (nitrofurantoin, trimethoprim) and the combined or progestogen-only pill. NHS and NICE guidance no longer recommends using additional contraception during a course of these antibiotics. However, if you experience vomiting or diarrhoea as a side effect, this may affect absorption — follow your pill’s patient information leaflet for guidance on this.
What is nitrofurantoin used for in cystitis?
Nitrofurantoin is the NICE first-line antibiotic for uncomplicated UTIs. It concentrates in the urine at the site of infection, making it highly effective for bladder infections. It must be taken with food to reduce stomach upset and is not suitable if kidney function is significantly impaired (eGFR <45 ml/min).
How long does nitrofurantoin take to work on a UTI?
Most people notice symptom improvement within a few days. Always complete the full prescribed course even if you feel better, to prevent the infection returning and antibiotic resistance developing.
Can I take trimethoprim and nitrofurantoin at the same time?
It is very unlikely a prescriber would recommend both simultaneously. Nitrofurantoin is prescribed first; if the infection proves resistant, trimethoprim or a different antibiotic is then prescribed separately after culture results.
References
- NICE. Urinary tract infection (lower) — women. Clinical Knowledge Summaries. cks.nice.org.uk
- NHS. Cystitis. nhs.uk/conditions/cystitis
- UKHSA. ESPAUR report 2023. gov.uk
- Electronic Medicines Compendium. Nitrofurantoin 100mg m/r capsules — SmPC. medicines.org.uk/emc
- Electronic Medicines Compendium. Trimethoprim 200mg tablets — SmPC. medicines.org.uk/emc
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. Nitrofurantoin and trimethoprim are prescription-only medicines — a medical consultation is required before they can be dispensed. If you have a fever, loin/back pain, or are pregnant, seek urgent in-person medical care. In a medical emergency, call 999.