Alternatives to Nitrofurantoin if You Can't Fill Your Prescription

Your doctor prescribed Nitrofurantoin for a urinary tract infection, but your pharmacy can't fill it. Now what? Whether it's a supply issue, a stock-out at your local pharmacy, or you've been told it's on back order, you need treatment — and you need it soon.

The good news is that several other antibiotics are proven to treat uncomplicated UTIs effectively. Here's what you should know about your options.

What Is Nitrofurantoin and How Does It Work?

Nitrofurantoin (brand names Macrobid and Macrodantin) is a nitrofuran antibiotic that has been treating UTIs since the 1950s. It works differently from most antibiotics: once inside bacterial cells, Nitrofurantoin is broken down into reactive compounds that simultaneously attack multiple targets — including DNA, RNA, and protein synthesis.

This multi-target approach is why Nitrofurantoin has remarkably low resistance rates — only about 1.6% of urinary E. coli isolates show resistance, compared to over 20% for some other common UTI antibiotics. It's also why the Infectious Diseases Society of America recommends it as a first-line treatment for uncomplicated cystitis.

Nitrofurantoin concentrates in the urine rather than building up in the bloodstream, which makes it effective for lower UTIs while minimizing systemic side effects. However, this also means it's not appropriate for kidney infections (pyelonephritis) — only for bladder-level UTIs.

Effective Alternatives to Nitrofurantoin

If you can't get Nitrofurantoin, these are the most commonly prescribed alternatives. Always consult your doctor before switching antibiotics — they'll consider your health history, allergies, local resistance patterns, and the severity of your infection.

1. Trimethoprim-Sulfamethoxazole (Bactrim, Bactrim DS)

Trimethoprim-Sulfamethoxazole (TMP-SMX), commonly known as Bactrim, is one of the most widely prescribed UTI antibiotics. It works by blocking two consecutive steps in bacterial folate synthesis, which bacteria need to make DNA.

• Typical dosage: One double-strength tablet (160 mg/800 mg) twice daily for 3 days
• Cost: Very affordable — as low as $4-$8 for a generic course with discount coupons
• Pros: Short treatment course, well-studied, widely available, inexpensive
• Cons: Higher resistance rates (exceeding 20% in many areas); not for patients with sulfa allergy; can interact with blood thinners like warfarin

2. Fosfomycin (Monurol)

Fosfomycin is unique among UTI antibiotics because it requires just a single dose. You mix one packet of granules in water and drink it — and your treatment is complete.

• Typical dosage: One 3-gram packet as a single dose
• Cost: More expensive — roughly $35-$75 with coupons for generic; brand Monurol can be over $100
• Pros: Single-dose convenience, low resistance rates, safe in pregnancy
• Cons: May be slightly less effective than multi-day courses of other antibiotics; more expensive; not available in all pharmacies

3. Cephalexin (Keflex)

Cephalexin is a first-generation cephalosporin antibiotic — related to penicillin — that's often used as a second-line option for UTIs.

• Typical dosage: 500 mg twice daily for 7 days
• Cost: Affordable generic — approximately $4-$15 with discount coupons
• Pros: Well-tolerated, widely available, inexpensive, safe in pregnancy
• Cons: Longer treatment course (7 days vs. 3-5); broader spectrum means more impact on gut bacteria; higher resistance rates for E. coli

4. Trimethoprim (Primsol)

For patients who are allergic to sulfa drugs and can't take Bactrim, Trimethoprim alone is an option. It targets the same bacterial pathway without the sulfamethoxazole component.

• Typical dosage: 100 mg twice daily for 3 days
• Cost: Generally $10-$25 with discount coupons
• Pros: Short course, avoids sulfa component
• Cons: Similar resistance patterns to TMP-SMX; less commonly stocked; may be harder to find than Bactrim

How to Switch Safely

If Nitrofurantoin isn't available, here's what to do:

1. Don't just stop looking. First, use Medfinder to check other pharmacies — Nitrofurantoin may be in stock nearby.
2. Contact your prescriber. Call your doctor's office and explain that the pharmacy can't fill Nitrofurantoin. They can call in an alternative prescription.
3. Consider telehealth. If your doctor isn't available quickly, a telehealth visit can get you a new prescription within hours.
4. Share your allergy and medication history. Some alternatives interact with specific medications or aren't suitable for certain conditions. Make sure your provider knows your full history.
5. Complete the full course. Whichever antibiotic you end up taking, finish the entire prescribed course — even if you feel better after a day or two.

Final Thoughts

Nitrofurantoin is an excellent UTI antibiotic, but it's not the only one. If you can't fill your prescription, effective alternatives exist. The most important thing is to get treated promptly — untreated UTIs can progress to kidney infections, which are much more serious.

Start by checking Medfinder for Nitrofurantoin availability. If it's truly unavailable, talk to your doctor about switching to one of the alternatives above. And if you want to understand more about what Nitrofurantoin is and how it works, we've got you covered.