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Cycloserine is used most often to treat tuberculosis, but it can also be used to treat bladder infections. Common side effects include headache, confusion, and feeling dizzy or lightheaded. Do not drive or do other activities that require alertness or coordination until you know how cycloserine affects you. It is important to complete your prescribed course of cycloserine, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to cycloserine or other similar medicines.

Uses

What is cycloserine used for?

Cycloserine is commonly used to treat tuberculosis (in combination with other medicines). Cycloserine can also be used to treat urinary (bladder) tract infections.

Cycloserine may also be used for other conditions as determined by your health care provider.

Cycloserine may not be appropriate for some of the infections listed above, depending on which germs are causing the infection. Bacteria in some locations may have developed resistance to cycloserine, which will make it not work as well.

How does cycloserine work (mechanism of action)?

Cycloserine works by interfering with the bacteria's cell wall, which is like their protective outer shell. By weakening this wall, it is harder for the bacteria to survive. This helps your body fight off the infection and get rid of the bacteria.

How is cycloserine supplied (dosage forms)?

Brands and other names

  • Seromycin

Dosage forms and strengths

  • 250 mg oral capsules

How should I store cycloserine?

Cycloserine should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of cycloserine?

The most common side effects of cycloserine are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Brain or central nervous system (CNS) problems (see below)
  • Allergic reactions (see below)

There may be other side effects of cycloserine that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of cycloserine?

While less common, the most serious side effects of cycloserine are described below, along with what to do if they happen.

Brain or Central Nervous System (CNS) Problems. Cycloserine can cause brain or central nervous system (CNS) problems. These may be more likely with higher doses. Call your health care provider right away if you have the following symptoms of brain or CNS problems.

  • Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
  • Feeling dizzy or lightheaded
  • Falling or losing consciousness
  • Headache
  • Sleepiness
  • Confusion or memory problems
  • Trouble saying words clearly
  • Seeing or hearing things that others do not see or hear, also called hallucinations
  • Muscle weakness
  • Increased irritability
  • Sudden change in mood or behavior, including depression or thoughts of suicide
  • Numbness, tingling, or burning in your arms, feet, or face

Severe Allergic Reactions. Cycloserine may cause allergic reactions, which can be serious. Stop taking cycloserine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use cycloserine?

Allergies to Ingredients. People who are allergic to any of the following should not take cycloserine.

  • Cycloserine
  • Seromycin
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific cycloserine products they stock.

Seizure Disorder. Cycloserine should not be used by people with a seizure disorder. 

Mental Health Problems. Cycloserine should not be used by people with certain mental health problems, such as psychosis, depression, or severe anxiety.

Kidney Problems. Cycloserine should not be used if your kidneys are not working as well as they should be. If there is a concern about the health of your kidneys, your health care provider may do tests to determine if they are working well enough to take this medicine.

Alcohol Use. Cycloserine should not be used in people who drink alcohol heavily. The risk of seizures is higher in these people. 

What should I know about cycloserine before using it?

Do not take cycloserine unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share cycloserine with other people, even if they have the same condition as you. It may harm them.

Keep cycloserine out of the reach of children.

Your health care provider will likely perform regular blood work while you are taking this medicine to check on the health of your liver, kidneys, and blood. The blood work can also help make sure the drug levels are safe and help with any needed dose changes. It is important to keep all appointments for blood work.

It is important to complete your prescribed course of cycloserine, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to cycloserine or other similar medicines.

Cycloserine can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how cycloserine affects you.

What should I tell my health care provider before using cycloserine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if cycloserine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • History of taking medicine to treat tuberculosis
  • Seizure disorders
  • Mental health problems
  • Kidney problems
  • Liver problems
  • Blood disorders
  • Drink alcohol often or in large amounts

Other Medicines and Supplements. Cycloserine may interact with other medicines and supplements. Before taking cycloserine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how cycloserine could affect pregnancy or harm an unborn baby. Tell your health care provider if you are pregnant or plan to become pregnant. Your health care provider will advise you if you should take cycloserine while you are pregnant or trying to get pregnant.

Breastfeeding. Cycloserine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will advise you if you should stop breastfeeding or stop cycloserine. 

Interactions

Does cycloserine interact with foods or drinks?

There are no known interactions between cycloserine and foods or drinks.

Drinking alcohol while taking cycloserine may increase the risk of seizures, dizziness, and confusion. It is best to avoid drinking alcohol while taking cycloserine.

Does cycloserine interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any other medicine to treat tuberculosis, including isoniazid, before taking cycloserine.

This may not be a complete list of medicines that can interact with cycloserine. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much cycloserine?

If you or someone else has used too much cycloserine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of cycloserine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses. 

It is important to complete your prescribed course of cycloserine, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to cycloserine or other similar medicines.