Isoniazid Medication: Uses, Dosage, and Side Effects Explained

Summary of Key Points

Isoniazid is a prescription medication used to both treat and prevent tuberculosis (TB) and related infections. It works by stopping the growth of the bacteria that cause TB. Often, it is used in combination with other medications to ensure the most effective treatment. It’s important to follow your healthcare provider’s instructions carefully and report any side effects you may experience. For personalized advice on Isoniazid, you can consult one of our telemedicine providers.

Names of Medication

US Brand Name: Nydrazid

Generic Name: Isoniazid

The generic name refers to the active ingredient in the medication and is listed in parentheses after the brand name.

Pharmacologic Category

Category: Antitubercular Agent

Isoniazid Dosage

Isoniazid is prescribed to treat various forms of tuberculosis and related bacterial infections. The dosage can vary depending on the condition being treated. Always consult your healthcare provider before making any changes to your dose. You can also schedule a telemedicine appointment with one of our providers for personalized dosing recommendations.

Tuberculosis (Active)

Dosage: 5 mg/kg (up to 300 mg) once daily or 15 mg/kg (up to 900 mg) 2-3 times per week.

Duration: Typically 6-9 months, depending on the severity of the infection and how well the patient responds to treatment.

Latent Tuberculosis Infection (LTBI)

Dosage: 300 mg once daily or 900 mg twice weekly.

Duration: 6-9 months, depending on individual risk factors and response to treatment.

Drug-Resistant Tuberculosis

Dosage: Isoniazid is often used in combination with other medications. The typical dose is 5 mg/kg (up to 300 mg) once daily, but this may vary based on the resistance profile of the bacteria.

Duration: Treatment can last 9-12 months or longer, depending on the severity of the infection.

HIV-Associated Tuberculosis

Dosage: 5 mg/kg (up to 300 mg) once daily or 15 mg/kg (up to 900 mg) 2-3 times per week.

Duration: Treatment typically lasts 6-9 months, but may be extended depending on the patient’s immune status and response to therapy.

Tuberculous Meningitis

Dosage: 5 mg/kg (up to 300 mg) once daily or 15 mg/kg (up to 900 mg) 2-3 times per week.

Duration: 9-12 months, depending on the severity of the infection and response to treatment.

Tuberculous Pleuritis

Dosage: 5 mg/kg (up to 300 mg) once daily or 15 mg/kg (up to 900 mg) 2-3 times per week.

Duration: Typically 6-9 months, depending on the severity of the infection.

Mycobacterial Infections

Dosage: 5 mg/kg (up to 300 mg) once daily or 15 mg/kg (up to 900 mg) 2-3 times per week.

Duration: The length of treatment depends on the specific type of mycobacterial infection and the patient’s response to therapy.

Bacterial Infections

Dosage: Isoniazid is not commonly used for standard bacterial infections but may be prescribed in specific cases. The typical dose is 5 mg/kg (up to 300 mg) once daily.

Duration: Varies depending on the infection and response to treatment.

Dosage Forms and Strengths

Tablets: 100 mg, 300 mg

Oral Solution: 50 mg/5 mL

Injectable Solution: 100 mg/mL

Administration Instructions for Isoniazid

Isoniazid should be taken on an empty stomach, either 1 hour before or 2 hours after meals. If it causes stomach discomfort, it can be taken with food, though this may reduce its effectiveness. It’s important to take the medication at the same time each day to maintain consistent levels in your body. If you miss a dose, take it as soon as you remember, but do not double up on doses. Be sure to complete the full course of treatment, even if you start feeling better, to prevent the infection from returning.

Isoniazid Side Effects and Adverse Reactions

Like all medications, Isoniazid can cause side effects. Some are more common than others, and not everyone will experience them. If you notice any side effects, contact your healthcare provider. You can also schedule a telemedicine appointment with one of our providers to discuss any concerns regarding Isoniazid side effects.

Common Side Effects of Isoniazid

Nausea and Vomiting: Some patients may experience stomach upset, including nausea or vomiting.

Fatigue: Feeling tired or fatigued is a common side effect of Isoniazid.

Numbness or Tingling: Isoniazid can cause peripheral neuropathy, which may feel like numbness or tingling in the hands or feet.

Serious Side Effects (Less Common)

Liver Damage (Hepatitis): Isoniazid can cause liver damage, especially in older adults or those who consume alcohol. Symptoms include yellowing of the skin or eyes (jaundice), dark urine, or severe stomach pain. These signs of liver toxicity should be reported immediately.

Severe Allergic Reactions: In rare cases, patients may experience severe allergic reactions, including rash, itching, or difficulty breathing.

Seizures: In rare instances, Isoniazid can cause seizures, particularly in patients with a history of epilepsy.

Contraindications for Isoniazid

A contraindication is a specific condition or situation where a drug should not be used because it may be harmful. If you have any of the following conditions, you should not take Isoniazid, or you should discuss with your healthcare provider whether the benefits outweigh the risks.

Acute liver disease: Isoniazid is processed by the liver, and if your liver is already damaged or inflamed, taking this medication could worsen your condition or lead to severe liver damage.

Previous allergic reaction to Isoniazid: If you have had an allergic reaction to Isoniazid in the past, taking it again could cause a severe allergic response, which could be life-threatening.

Severe kidney disease: Isoniazid can accumulate in the body if your kidneys are not functioning properly, leading to toxicity and increased side effects.

History of severe mental health conditions: Isoniazid can cause mood changes, including depression and psychosis, and may worsen pre-existing mental health conditions.

If you have any of these conditions, it’s important to consult with one of our telemedicine providers before starting Isoniazid. We can help you determine the safest treatment plan for your specific health needs.

Drug to Drug Interactions

Isoniazid can interact with other medications, potentially increasing the risk of side effects or reducing the effectiveness of your treatment. It’s important to inform your healthcare provider about all the medications you are currently taking, including over-the-counter drugs and supplements. Some common drug interactions with Isoniazid include:

1. Phenytoin (Dilantin): Isoniazid can raise phenytoin levels in your blood, which may lead to toxicity.
2. Carbamazepine (Tegretol): Isoniazid may increase carbamazepine levels, heightening the risk of side effects such as dizziness and drowsiness.
3. Acetaminophen (Tylenol): Combining Isoniazid with acetaminophen can elevate the risk of liver damage.
4. Alcohol: Consuming alcohol while taking Isoniazid significantly increases the likelihood of liver damage.
5. Rifampin (Rifadin): Using Isoniazid alongside Rifampin can raise the risk of liver toxicity.

Always consult one of our healthcare providers through telemedicine before starting or stopping any medications while taking Isoniazid.

Isoniazid in Pregnancy

Is it Safe to Take Isoniazid During Pregnancy?

Isoniazid is generally considered safe during pregnancy, especially if you have active or latent tuberculosis, as untreated tuberculosis poses significant risks to both the mother and baby. However, Isoniazid can increase the risk of liver damage, which may be more pronounced during pregnancy. Your healthcare provider may recommend taking vitamin B6 (pyridoxine) alongside Isoniazid to help reduce side effects. Always consult your healthcare provider before starting Isoniazid if you are pregnant or planning to become pregnant.

Isoniazid while Breastfeeding

Is it Safe to Take Isoniazid While Breastfeeding?

Isoniazid does pass into breast milk, but the amount is typically too low to harm a nursing infant. However, breastfed infants of mothers taking Isoniazid should be monitored for any signs of side effects, such as jaundice or liver issues. Your healthcare provider may also recommend vitamin B6 supplements for both you and your baby to reduce the risk of side effects. As always, consult with your provider before making any decisions about breastfeeding while on Isoniazid.

Estimated Cost of Isoniazid Medication

The cost of a 30-day supply of Isoniazid without insurance can vary depending on the pharmacy and location. Using a GoodRx coupon, the estimated cost ranges from $10 to $20 for a 30-day supply of 300 mg tablets. Prices may fluctuate, so it’s a good idea to check with your pharmacy or use a coupon service like GoodRx for the most up-to-date pricing.

Possible Alternatives to Isoniazid

If Isoniazid is not suitable for you, alternative treatments and lifestyle changes may help manage your condition. Always discuss these options with your healthcare provider before making any changes to your treatment plan. You can also schedule a telemedicine appointment with one of our providers to explore these alternatives.

1. Tuberculosis: Alternatives include Rifampin (Rifadin), Ethambutol (Myambutol), and Pyrazinamide. Lifestyle changes, such as maintaining a healthy diet and avoiding alcohol, can support your treatment.
2. Latent tuberculosis infection: Rifampin or a combination of Rifapentine and Isoniazid may be used as alternatives. Regular monitoring and a healthy lifestyle are important to prevent progression to active tuberculosis.
3. Bacterial infections: Depending on the type of infection, antibiotics like Amoxicillin (Amoxil) or Doxycycline (Vibramycin) may be prescribed. Good hygiene and a balanced diet can help prevent bacterial infections.
4. Mycobacterial infections: Other antibiotics, such as Clarithromycin (Biaxin) or Azithromycin (Zithromax), may be used. Supporting your immune system with good nutrition and regular exercise is key to fighting these infections.
5. Pulmonary tuberculosis: Rifampin, Ethambutol, and Pyrazinamide are commonly used alongside Isoniazid. Quitting smoking and avoiding pollutants can improve lung health.
6. Extrapulmonary tuberculosis: Treatment is similar to pulmonary TB, often involving Rifampin, Ethambutol, and Pyrazinamide. Maintaining a strong immune system through a healthy lifestyle is essential.
7. Drug-resistant tuberculosis: Treatment may involve second-line drugs like Bedaquiline (Sirturo) or Linezolid (Zyvox). Close monitoring and strict adherence to medication are crucial for managing drug-resistant TB.
8. HIV-associated tuberculosis: Treatment may include a combination of anti-TB drugs and antiretroviral therapy (ART). It’s important to work closely with your healthcare provider to manage both conditions effectively.
9. Tuberculous meningitis: Treatment often involves a combination of Isoniazid, Rifampin, Pyrazinamide, and Ethambutol. Corticosteroids may also be prescribed to reduce inflammation. Early diagnosis and treatment are critical.
10. Tuberculous pleuritis: Treatment is similar to pulmonary TB, with a combination of antibiotics. Draining fluid from the pleura may also be necessary. Maintaining good lung health is important for recovery.

Recent Updates on Isoniazid Research

Recent studies have focused on improving the safety and effectiveness of Isoniazid, particularly in patients with latent tuberculosis infection. One ongoing area of research is the development of shorter treatment regimens that combine Isoniazid with other medications, such as Rifapentine, to reduce the duration of therapy while maintaining its effectiveness. Another area of interest is the use of Isoniazid in combination with newer drugs for treating drug-resistant tuberculosis.

Researchers are also investigating genetic factors that may influence how patients metabolize Isoniazid, which could lead to more personalized treatment plans in the future. Stay informed and discuss any new research findings with your healthcare provider. If you have questions about your treatment, you can schedule a telemedicine appointment with one of our providers to get the latest information and personalized advice.

James Kingsley

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