Nitrofurantoin is one of the most popular antibiotics to treat urinary tract infections. After being absorbed from the gut and filtered by the kidneys, the drug accumulates in the acidic urine, disrupting the genetic material of bacteria, and killing them effectively. Despite being a highly effective treatment often prescribed by doctors, nitrofurantoin still has some adverse effects on the body. In today’s guide, we’ll highlight everything you need to know about the side effects of nitrofurantoin. So without further ado, let’s dive right in!
Nitrofurantoin’s Common Side Effects
Nitrofurantoin is commonly used for treating and preventing lower urinary tract infections because it’s generally effective with acute side effects on most users.
According to drug reports, nitrofurantoin’s most common side effects are nausea, stomach upsets, vomiting, and loss of appetite.
In some patients, these side effects are also accompanied by diarrhea.
Other non-serious and less common side effects include headaches, flatulence, vaginal itching and discharge in women, and dark (rust-colored) urine.
It would help if you also kept in mind that even the common symptoms are less frequent in modern formulations of the drug, especially the macrocrystalline form.
Altering the crystal size of the drug significantly impacts the gastrointestinal absorption of nitrofurantoin, and therefore, it can reduce the previously mentioned symptoms significantly.
Side Effects Of Nitrofurantoin in the Elderly
In general, elderly patients who take nitrofurantoin can experience similar symptoms to those of healthy adults. However, nitrofurantoin side effects among older patients are more likely to occur.
These symptoms include:
- Nausea and vomiting
- General weakness and drowsiness with or without muscle and joint pain
- Indigestion and loss of appetite, along with flatulence
- Rash and hives with itching
- Discoloration of urine
- Temporary hair loss
- Confusion and vertigo
- Sore throat and inflammation of salivary glands
- Rigors or shivering chills
Side Effects of Nitrofurantoin in Adults
As previously established, mild nitrofurantoin side effects are usually the most common ones, such as nausea, loss of appetite, headache, vomiting, and mild diarrhea to a lesser extent.
In addition to these side effects, nitrofurantoin has more severe side effects, but luckily, they’re less common than the milder ones. These adverse reactions include:
Severe watery or bloody diarrhea
Increased pressure inside the skull can cause painful headaches, ear ringing, and blurred vision.
Hemolysis: Red blood cell damage that results in tiredness and pale skin.
Respiratory inflammation: This rare possible side effect can occur after taking the medication for a very long time (over 6 months). The inflammation is usually accompanied by high fever, coughing, shortness of breath, and sudden chest pain.
Nerve ending damage: This side effect is quite rare and mainly targets the hands and feet, causing numbness or tingling sensations in the hands or feet.
Liver inflammation: This is also associated with the long-term use of nitrofurantoin. Symptoms of liver inflammation are similar to jaundice, including the white of the eyes yellowing, dark urine and stool, and yellowing of the skin.
Easy bruising, and unexplained bleeding, especially for the nose, are also possible side effects.
Most of these symptoms should subside gradually after you stop nitrofurantoin. However, you need to inform your healthcare provider if you experience any of them immediately.
Nitrofurantoin Warnings for People With Certain Health Conditions
Some health conditions might impact how nitrofurantoin functions or increase the likelihood of side effects.
You shouldn’t take nitrofurantoin if:
You’re allergic to nitrofurantoin or any other ingredients (active or inactive) in the medication
You suffer from kidney disease or any form of renal impairment (the drug relies on kidneys for filtration and excretion – your creatinine clearance should be higher than 40 mL/min)
You’re dehydrated or suffer from a condition that prevents you from urination or causes you to urinate less than usual (the drug is selectively concentrated in urine)
You suffer from liver problems or have a history of jaundice (increases the likelihood of liver inflammation as a side effect)
You have glucose-6-phosphate dehydrogenase (G6PD) deficiency (also related to liver problems)
You have diabetes, anemia, electrolyte imbalance, or vitamin B deficiency (conditions that affect the rate of filtration and absorption of nitrofurantoin)
You’re pregnant in the last trimester (the FDA categorizes nitrofurantoin as category B, so it’s safe during early pregnancy but might harm your baby during later stages)
You’re breastfeeding (nitrofurantoin passes into breast milk and can harm your baby, as nitrofurantoin is not recommended for one-month-old infants and younger)
How to Avoid Nitrofurantoin Side Effects
Although nitrofurantoin side effects are mostly mild, you can still avoid them or reduce their impact with some specific actions. Here are some tips that can reduce certain side effects of the antibiotic:
Avoid taking nitrofurantoin on an empty stomach. Although the best time to take the medicine is during or after eating, even a small snack can significantly reduce stomach upset.
Make sure you’re adequately hydrated and drink enough water along with the pills.
Avoid heavy or spicy food.
Please don’t drink too much alcohol because it’ll increase the chances of headaches and liver problems.
Take OTC painkillers that don’t require a prescription with nitrofurantoin if you have a mild headache, such as acetaminophen and ibuprofen.
How Long Do Nitrofurantoin Side Effects Last?
Some nitrofurantoin side effects would go away as soon as you stop the medication, while others would last for a very long time.
For example, mild side effects like headaches, nausea, vomiting, and diarrhea might last only a few hours after taking the medication and will go away quickly once you stop taking the drug.
On the other hand, chronic side effects due to extended use usually last a lot longer once they show up.
For instance, liver inflammation symptoms might last up to 6 or more months before they subside, while red blood cell damage lasts only 2 to 4 months.
Nitrofurantoin Interactions With Other Medications
In addition to common and uncommon side effects, nitrofurantoin might interact with several medicines and compounds. Here are some of the most popular interactions with other medications.
Magnesium Trisilicate (antacid): This increases the stomach pH level, decreasing nitrofurantoin’s absorption rate and effectiveness.
Probenecid (Gout medication): This reduces the concentration of nitrofurantoin in urine and increases nitrofurantoin’s concentration in the blood. This lowers its effectiveness and increases its toxicity and side effects.
Methotrexate (Immunosuppressant): Concurrent use with nitrofurantoin increases the risk of lung-related side effects.
Certain Vaccines (Especially Cholera and Typhoid Vaccines): Nitrofurantoin can reduce the effectiveness of these medications.
Sodium picosulfate (stimulant laxative): loses its effectiveness in the presence of nitrofurantoin.
Some Urine-Based Lab Tests: might impact the results. For example, it gives a false positive for glucose in urine.
Nitrofurantoin might also interact with other medications, so you must consult a pharmacist before taking any nitrofurantoin or combining it with new treatments.
Nitrofurantoin Food Interactions
In addition to medications and lab tests, nitrofurantoin might interact with some food and drinks. This includes:
Magnesium-rich foods: This includes foods like pumpkin seeds, nuts, chia seeds, soy milk, and oatmeal, which decreases the absorption of the drug
Caffeinated drinks: tea, coffee, and soda drinks all have caffeine, which is a natural diuretic that reduces the effectiveness of nitrofurantoin and causes dehydration
What Happens If I Miss a Dose of Nitrofurantoin?
If you miss a nitrofurantoin dose, you’ll need to check the time and see how long it is left until the next dose.
If you still need to get your dose by up to 5 hours: You should take it immediately, then take your next dose at its original time.
If there’s less than an hour left before your next dose: Skip the dose and take your next one on time, then continue on your schedule while adding an extra dose at the end.
What Happens If I Overdose on Nitrofurantoin?
The maximum allowed daily dose of nitrofurantoin is usually 400 mg. Going past these limits puts you at risk of nitrofurantoin toxicity, with typical symptoms of stomach upsets, vomiting, nausea, and blurred vision.
In most cases, taking an extra dose won’t cause serious harm, so you shouldn’t worry much about it. However, if you feel too unwell or take several doses above the daily limit, you should seek immediate medical attention.
When to See A Doctor
If the side effects of nitrofurantoin are limited to headache, nausea, stomach upsets, and other mild symptoms, you don’t have to worry about it.
However, if the side effects worsen or the UTI symptoms don’t ease in a couple of days, you should contact your medical specialist to prescribe another treatment.
Frequently Asked Questions (FAQs)
Like all medicines, nitrofurantoin can cause several side effects. Luckily, most common side effects are relatively mild and tolerable. Still, there are some severe adverse reactions that you should keep in mind, especially during long-term use.
Nitrofurantoin can kill various gram-positive and gram-negative bacteria, including S. saprophyticus and E. Coli, which are commonly responsible for lower urinary tract infections.
However, nitrofurantoin is not a broad-range antibiotic that you can use for other types of infections, as it specializes in UTIs due to its selective concentration in urine.
Regarding urinary tract infections, nitrofurantoin is a powerful and highly effective antibiotic.
According to various studies of its impact, nitrofurantoin has a cure rate of up to 94% when a proper dosage is followed.
The treatment is also used to prevent infections in susceptible patients with lower side effects than alternatives.
Nitrofurantoin can cause gastric upsets and pain in the upper abdomen. In addition, this pair might spread to the back along with other side effects, although it’s not common.
Ideally, your doctor will prescribe nitrofurantoin for between 3 to 5 days and up to 7 days in some cases. The decision depends on various factors and risk factors, including the severity of the infection.
For the success of the treatment and the prevention of side effects and relapses, you should follow the schedule of the doses properly and avoid taking the medication for longer or fewer days, even if you feel better already.
The highest safe dose of nitrofurantoin is 400 mg daily, which is usually divided into 2 to 4 doses of 100 or 50 mg, respectively.
Nitrofurantoin has a half-life time of less than an hour. The drug stays in your system for up to 5 hours. The remaining traces of the drug should be out of your system in about 3 days, but keep in mind that some renal conditions might keep the nitrofurantoin in your system for longer.
The best way to reduce nitrofurantoin side effects is by taking it during meals or after a snack. This reduces stomach upsets, nausea, and flatulence significantly. Taking the pills with several sips of water would be best to rehydrate your body since the drug is concentrated in the urine.
The side effects of nitrofurantoin usually last for several hours, but the exact duration varies from one person to another. Chronic side effects from long-term use usually last the longest, while others will go away immediately after you start the treatment.
It would be best to avoid any treatments that might interact with nitrofurantoin, such as magnesium antacids, methotrexate, sodium picosulfate, and probenecid. You should also avoid magnesium and caffeine-rich food and drinks.
Macrobid is made up of nitrofurantoin monohydrate/macrocrystals. About 75% of the drug is nitrofurantoin monohydrate, and 25% is nitrofurantoin macrocrystals.
Final Thoughts
As you can see, the most common nitrofurantoin side effects are nausea, loss of appetite, and vomiting. You can reduce these side effects by taking the medication with or directly after a snack. Nitrofurantoin also come in brand names like Furadantin, Macrobid, Aratoin, and Macrodantin.
However, there are also rare but more serious adverse reactions like bruising on the skin, liver problems, lung problems, and high fever.
If you notice any of these symptoms or have any concerning reactions after taking nitrofurantoin, you should seek immediate health care.
