Nitrofurantoin

Benjamin Clanner-Engelshofen is a freelance writer in the medical department. He studied biochemistry and pharmacy in Munich and Cambridge / Boston (USA) and noticed early on that he particularly enjoyed the interface between medicine and science. That is why he went on to study human medicine.

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The active ingredient nitrofurantoin is an antibiotic and is used to treat bacterial urinary tract infections. Although it was previously only used as a second-choice antibiotic, it has been a first-choice agent again since 2011, according to the current therapy guidelines. Here you can read more about the effects and use of nitrofurantoin, side effects and other important information.

This is how nitrofurantoin works

The antibiotic nitrofurantoin is a so-called prodrug: it is only converted into its active form at the site of action (in the urinary tract). The conversion takes place through bacterial enzymes after the active ingredient has been absorbed into the blood from the intestine and as soon as it is released to the outside via the urinary tract: Nitrofurantoin penetrates the bacteria located here in the event of a urinary tract infection. Inside the bacterial cells, certain enzymes (nitroreductases), which do not occur in humans, convert nitrofurantoin into the active, effective form. This attacks the bacterial genetic material and breaks it up, but also has a targeted destructive effect on other metabolic enzymes that are essential for the cell.

Because the active form of nitrofurantoin has many different points of attack in the bacterial cell, the likelihood that the bacteria will develop resistance to the antibiotic is very low.

The antibiotic not only inhibits the growth of bacteria, but also selectively kills them, which is why nitrofurantoin is called a “bactericidal antibiotic”.

Uptake, breakdown and excretion of nitrofurantoin

Nitrofurantoin peaks in urine around four to five hours after ingestion. Around half of the active ingredient ingested is broken down into ineffective metabolic products. These are also excreted in the urine and can lead to a harmless brown coloration of the urine.

When is nitrofurantoin used?

The antibiotic nitrofurantoin is used to treat acute, uncomplicated cystitis."Uncomplicated" means that there are no symptoms that suggest worse illnesses or disease progression - such as fever, nausea, vomiting, kidney, back or flank pain, vaginal itching or discharge.

In certain cases, such as congenital or acquired narrowing of the lower urinary tract or repeated, chronic urinary tract infections, preventive treatment with nitrofurantoin may also be considered.

In the case of an acute infection, nitrofurantoin is usually used for five to seven days; as a preventive measure, it can last up to a maximum of six months, albeit in a lower dose.

This is how nitrofurantoin is used

Nitrofurantoin is usually taken in three to four single doses of 100 milligrams throughout the day. In the case of capsules with delayed release of active ingredients (so-called "retard capsules"), the dosage is reduced to two to three capsules of 100 milligrams. It is taken every six to eight hours with a meal and a glass of water.

In the case of an acute infection, the antibiotic should be taken for as long as prescribed by the doctor - even if the symptoms improve beforehand.

Lower doses are chosen for preventive intake, usually one tablet in the evening after the last urination.

What are the side effects of nitrofurantoin?

During therapy with nitrofurantoin, more than ten percent of those treated experience side effects such as dizziness, impaired movement coordination, eye tremors, allergic reactions such as itching, reddening, rash and water retention in the tissue. If allergic reactions occur, a doctor should be informed.

Other nitrofurantoin side effects affecting one in ten to one hundred patients include headache, loss of appetite, nausea, vomiting, pneumonia, cough, and chest pain.

What should be considered when taking nitrofurantoin?

In general, there are relatively few interactions between nitrofurantoin and other active ingredients, as the drug is only activated and effective in the urine. However, some agents can hinder the absorption of the antibiotic from the intestines, such as heartburn agents (such as magnesium or aluminum salts) and anti-nausea agents (such as metoclopramide).

Agents that dampen the parasympathetic nervous system (such as atropine or propantheline) delay the absorption of nitrofurantoin in the intestine and its excretion in the urine, but this is not in principle a disadvantage.

Drugs and foods that make the urine alkaline (such as many types of vegetables, citrus fruits or milk) inhibit the excretion of nitrofurantoin. Substances acidifying the urine (such as meat), on the other hand, promote excretion.

Since the use of nitrofurantoin can lead to vomiting and diarrhea, oral contraceptive agents may not be sufficiently safe. Additional contraceptive measures should be taken in the affected cycle.

Nitrofurantoin should not be used in pregnant and breastfeeding women, as animal experiments may have shown harmful effects on the child. Infants should receive the active ingredient in a correspondingly reduced dosage after the third month of life at the earliest. The dose also needs to be reduced in children and adolescents.

In elderly patients and patients with kidney problems, it is important to have a kidney function test before using nitrofurantoin to check whether the antibiotic can be used.

In general, you should always drink a lot with urinary tract infections.

How to get drugs with nitrofurantoin

Medicines with the active ingredient nitrofurantoin can be obtained from pharmacies according to a doctor's prescription.

How long has nitrofurantoin been known?

The search for chemically produced antibiotics of the nitrofuran type began as early as the 1940s. This led to the discovery of nitrofurantoin, which only achieved sufficient concentrations in the urine, but which was precisely why it was used for urinary tract infections from the mid-1950s. Generics with the active ingredient nitrofurantoin are also available in Germany.

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