Order Isoniazid (Isoniazid) tablets online in the USA

Product Name	Isoniazid
Dosage	100 mg, 300 mg
Active Ingredient	Isoniazid
Form	Oral Tablets
Description	Prescription therapy in the USA for latent tuberculosis infection (LTBI) and, in combination with other drugs, active TB disease. Requires medical oversight, liver safety monitoring, and often vitamin B6.
How to Order in the USA	Valid prescription or online consultation where permitted

Isoniazid has been a foundational tuberculosis (TB) medicine in the United States for decades and remains a first-line option recommended by national guidelines. In the U.S., it is dispensed by prescription and commonly provided as 100 mg and 300 mg oral tablets; oral liquid formulations are also available through certain pharmacies. Isoniazid can be used as a single agent to treat latent TB infection (LTBI) and, for active TB disease, it is used together with other anti-tuberculosis medicines as part of a multidrug regimen. Because TB treatment is a public health priority in the USA, access to isoniazid is supported by clinics, health departments, and pharmacies working in concert to help patients start therapy promptly and adhere safely to the complete course.

This medication may also be referred to by historical brand names such as Nydrazid, though isoniazid is most often dispensed as a generic product in the United States. Care models vary by state, but many Americans receive isoniazid through primary care offices, infectious diseases practices, TB clinics, and local or state health departments that follow CDC, ATS, and IDSA guidance. Because isoniazid can affect liver function and interact with other medicines, U.S. clinicians typically recommend baseline and periodic assessments, emphasize avoidance of alcohol, and suggest vitamin B6 (pyridoxine) supplementation for patients at higher risk of neuropathy. If you are beginning TB prevention or treatment, a licensed U.S. prescriber will determine if isoniazid is right for you, select the appropriate dose based on your weight and clinical status, and advise on the safest way to take the medication at home or via directly observed therapy (DOT).

Isoniazid price in the USA

Isoniazid is widely available in generic form nationwide, which helps keep costs relatively low compared with many brand-only therapies. Pricing varies by strength, pharmacy, insurance coverage, and discount programs. Many patients with health insurance in the United States pay only a modest copay for a month’s supply. For the uninsured, independent and chain pharmacies often accept manufacturer-independent discount cards and coupons, lowering out-of-pocket expenses substantially. Because dosing schedules may be daily, twice weekly, or weekly depending on regimen, the actual monthly cost for you will depend on the precise prescription your clinician chooses, whether therapy is for LTBI monotherapy or for active TB in combination with other medications.

Typical adult tablet strengths are 100 mg and 300 mg. For adults, a common maintenance dose for many regimens is 300 mg by mouth once daily, while alternative intermittent regimens can use higher per-dose amounts under clinical supervision or DOT. Pediatric dosing is based on weight and is carefully calculated in accordance with guideline ranges. From a budget perspective, a 30-day supply of generic isoniazid tablets is generally affordable at many U.S. pharmacies. If cost is a concern, speak to your prescriber or pharmacist about local public health programs, TB clinic resources, and patient assistance options in your state; these programs frequently help cover medication and monitoring.

For people being treated for active TB, the overall medication cost reflects all components of the regimen. Isoniazid is only one piece of combination therapy that can also include rifampin or rifapentine, pyrazinamide, and ethambutol during the intensive phase. Public health departments often coordinate services for active TB to ensure quick access to the full regimen, including lab testing and adherence support, which can reduce the total cost to patients and optimize outcomes.

Because prices fluctuate, we recommend verifying current U.S. retail costs with your local pharmacy, your health plan’s drug formulary, or your TB program coordinator. Your clinician can also advise on the most cost-effective regimen that still meets clinical goals and aligns with your personal circumstances, especially if you are considering a shorter-course regimen such as 3 months of weekly isoniazid plus rifapentine (3HP) for latent TB.

Where can I get isoniazid in the USA?

 In the United States, isoniazid is a prescription-only medication. You can obtain it through a licensed healthcare provider after appropriate TB evaluation, which may include testing for latent TB infection (e.g., IGRA blood test or tuberculin skin test), chest imaging, and clinical assessment. Many U.S. patients fill their isoniazid prescriptions at local retail pharmacies or receive their medicines through TB clinics and health department programs that coordinate delivery and follow-up. Some services may offer telehealth consultations, where legally permitted, to help initiate care and provide ongoing monitoring without unnecessary delays.

Our platform connects patients with trusted, U.S.-based pharmacy services and healthcare professionals who can help ensure therapy is safe, evidence-based, and consistent with current guidelines. We emphasize proper diagnostic steps, counseling on side effects and interactions, and routine follow-up so that every patient starts therapy with a clear plan. If you have a positive TB test or a known exposure, seek medical advice promptly: early evaluation and the right regimen reduce the chance of progression from latent infection to active disease and help protect your community.

For individuals with barriers to in-person care, remote support may assist with adherence and symptom check-ins. Where state law allows, clinicians may use telemedicine to renew prescriptions, counsel on dose timing, and arrange lab monitoring. If you are unsure how to begin, contact your local health department or speak with your primary care provider, who can guide you to the right care pathway for your situation.

Isoniazid in the USA: access and care coordination

Getting started typically involves confirming the diagnosis (latent versus active disease), verifying the absence of drug resistance when indicated, and choosing a regimen that you can complete successfully. In the USA, shorter-course regimens for LTBI are favored because they are easier to finish, but your provider may still recommend 6–9 months of daily isoniazid when clinically appropriate. Care teams also check your current medications for interactions, review your alcohol intake, discuss vitamin B6 supplementation, and set up a plan for monitoring. Remember that completing the full course is essential—TB medicines work best when taken exactly as prescribed without gaps.

What is isoniazid?

 Isoniazid is an antibacterial medicine specifically active against Mycobacterium tuberculosis, the bacterium that causes TB. It is a prodrug activated by the bacterial enzyme KatG; once activated, it targets enzymes involved in mycolic acid synthesis (such as InhA), which are critical components of the mycobacterial cell wall. By interrupting mycolic acid production, isoniazid compromises the integrity of the cell wall, leading to bacterial death. The agent is bactericidal against rapidly dividing organisms and can be bacteriostatic against slowly replicating populations, which is why combination therapy and adequate treatment duration are essential in active TB.

In clinical practice across the USA, isoniazid is used for two main purposes: preventing active disease in people with latent TB infection and treating active TB disease as part of a multidrug regimen. When used to prevent TB, isoniazid is administered alone or with a rifamycin for a defined period to eradicate dormant bacteria and reduce the lifetime risk of developing active disease. For active TB disease, it is paired with other agents (commonly rifampin or rifapentine, pyrazinamide, and ethambutol) during the intensive phase, followed by a continuation phase with fewer drugs once the bacterial burden is lower and susceptibility is confirmed.

Because isoniazid is highly effective yet associated with potential liver toxicity and peripheral neuropathy, U.S. clinicians recommend careful baseline assessment, education on warning symptoms (such as fatigue, abdominal pain, dark urine, or jaundice), and prudent use of vitamin B6 to help reduce neuropathy risk. With appropriate monitoring and adherence, isoniazid remains one of the most successful tools for TB control in the United States.

Isoniazid for latent tuberculosis infection (LTBI)

 Treating LTBI is a key public health strategy in the USA because it prevents progression to active disease, especially in people at higher risk such as recent contacts of active TB cases, immunocompromised individuals, and those with medical conditions that increase TB risk. Isoniazid monotherapy for 6 or 9 months (often referred to as 6H or 9H) is a long-standing, guideline-supported option. Daily dosing is the standard approach, and patients receive counseling to avoid alcohol and to promptly report any symptoms suggestive of liver irritation.

Shorter-course options that include isoniazid are also available. A widely used regimen is 3HP, which combines once-weekly isoniazid with rifapentine for 12 doses under appropriate supervision. Another alternative is 3HR, consisting of daily isoniazid plus rifampin for 3 months. Your healthcare provider will help determine which option best matches your medical history, drug interactions, and likelihood of completing therapy. Regardless of the regimen, adherence is crucial—finishing the full course is the best way to protect your long-term health and prevent community transmission.

Vitamin B6 supplementation is routinely recommended in several situations (for example, pregnancy, diabetes, HIV infection, alcoholism, malnutrition, chronic kidney disease, or existing neuropathy) to reduce the risk of tingling or numbness in hands and feet. In addition, clinicians often arrange periodic check-ins by phone or telehealth to reinforce adherence, review any new medications, and ensure that side effects are addressed quickly if they arise.

Why treating LTBI matters

Most people with latent TB feel completely well and have no symptoms, which can make treatment seem less urgent. However, without therapy, latent TB can reactivate later in life and cause contagious disease. U.S. data show that a significant proportion of active TB cases arise from reactivation of LTBI, which is why preventive treatment is a priority. By completing an isoniazid-containing regimen, you substantially reduce your lifetime risk of developing active TB, protecting both yourself and those around you. Treating LTBI is especially important for people starting immunosuppressive therapy, those with recent TB exposure, and individuals with medical conditions that make reactivation more likely.

Isoniazid in active tuberculosis (combination therapy)

 For active TB disease, isoniazid must be used in combination with other first-line TB medications to prevent the emergence of resistance and to achieve microbiologic cure. A common U.S. regimen begins with an intensive phase of isoniazid, rifampin (or rifapentine in select protocols), pyrazinamide, and ethambutol (often abbreviated as “RIPE”), typically for two months. Once drug susceptibility testing confirms isoniazid and rifampin sensitivity and clinical improvement is documented, the continuation phase usually proceeds with isoniazid plus rifampin for several additional months, completing a standard 6-month total course in many uncomplicated pulmonary TB cases.

Complex scenarios—such as drug resistance, extrapulmonary involvement, HIV co-infection, or intolerance to one or more agents—require individualized plans developed by specialists following CDC/ATS/IDSA recommendations. Throughout therapy, periodic clinical evaluations, sputum cultures where applicable, and safety labs are used to track progress and catch potential adverse effects early. The combination approach, when taken exactly as prescribed, achieves high cure rates and reduces transmission in the community.

How does isoniazid work?

Isoniazid is activated inside Mycobacterium tuberculosis cells and then inhibits enzymes needed for mycolic acid synthesis, leading to defective cell walls and bacterial death. It is particularly active against rapidly dividing organisms in the early phase of treatment, which helps to quickly reduce the bacterial load when used in combination regimens. Because it acts on a specific bacterial pathway, isoniazid does not treat viral illnesses and is not used for non-mycobacterial infections. Its unique mechanism makes it indispensable in TB programs worldwide, including across the United States.

Monitoring and safety: liver function and boxed warning

 Isoniazid carries a boxed warning for the risk of severe—even fatal—hepatitis. Although this reaction is uncommon, especially in younger adults, the risk rises with age, alcohol use, pre-existing liver disease, and the immediate postpartum period. U.S. clinicians counsel patients to avoid alcohol completely while on isoniazid and to report symptoms of liver irritation right away, including fatigue, weakness, nausea, loss of appetite, persistent upper abdominal pain, dark urine, or yellowing of the skin or eyes. If such symptoms occur, prompt laboratory evaluation is necessary, and isoniazid may be paused or stopped. Routine baseline liver function tests are often obtained for patients with risk factors, and periodic monitoring may be recommended during therapy.

In addition to hepatic monitoring, teams look out for peripheral neuropathy—manifesting as tingling, burning, or numbness in the hands or feet. This risk is higher in people with diabetes, HIV, chronic kidney disease, malnutrition, alcoholism, pregnancy, or pre-existing neuropathy. Vitamin B6 supplementation is usually prescribed in these groups to reduce the likelihood of nerve-related symptoms. Clinicians also review each patient’s current medications for possible interactions, advise on diet and timing of doses, and offer practical strategies to boost adherence. With these safety steps in place, isoniazid remains a well-tolerated and highly effective TB medicine for most people.

Pyridoxine (vitamin B6) with isoniazid

 Isoniazid can interfere with vitamin B6 metabolism, which may contribute to neuropathy. To prevent this, many U.S. clinicians recommend daily vitamin B6 (pyridoxine) during isoniazid therapy for at-risk patients and sometimes for all adults as a simple precaution. A common adult preventive dose is 25–50 mg of pyridoxine daily. In children, dosing is weight-based and determined by the pediatric provider. If neuropathy symptoms develop despite prevention, the pyridoxine dose may be adjusted, and your provider will reassess ongoing therapy, other risk factors, and alternative causes.

Vitamin B6 is generally well tolerated, but very high doses taken long term can themselves cause neuropathy, so it is important to use the dose recommended by your clinician and avoid additional over-the-counter vitamin B6 without discussing it first. Keep an updated list of all supplements and medications you take, and share it with your care team to ensure safe, coordinated therapy.

In lactating parents taking isoniazid, some clinicians provide pyridoxine to the breastfeeding individual and may recommend vitamin B6 for the infant if the infant is also receiving isoniazid. Pediatric specialists will tailor prevention and monitoring plans to each child’s needs, balancing efficacy and safety.

Pharmacology and action

 After oral administration, isoniazid is rapidly absorbed and widely distributed, including into the cerebrospinal fluid. It undergoes hepatic acetylation via N-acetyltransferase (NAT2), and individuals can be slow or rapid acetylators based on genetics, which affects serum levels and potential susceptibility to adverse effects. The drug is primarily eliminated by the kidneys as metabolites. Food—especially high-fat meals—can reduce and delay absorption, which is why U.S. labeling commonly recommends taking isoniazid on an empty stomach, unless gastrointestinal upset necessitates taking it with a light snack. Its selective activity against mycobacteria and strong early bactericidal effect underpin its central role in TB regimens.

Because of its metabolic pathway, isoniazid can inhibit certain cytochrome P450 enzymes, leading to elevated levels of co-administered drugs such as phenytoin and carbamazepine. Understanding these pharmacologic interactions helps clinicians prevent toxicity and adjust doses proactively. Your pharmacy team will review your full medication profile at each visit to confirm safe, effective co-therapy tailored to your situation.

Safety

When prescribed and monitored appropriately in the USA, isoniazid is generally safe and effective for the majority of patients. The most clinically significant risks are hepatotoxicity and peripheral neuropathy, with additional rare events including rash, drug fever, hematologic reactions (such as anemia), lupus-like syndrome, and central nervous system effects (such as seizures or mood changes) in susceptible individuals. The likelihood of serious liver reactions increases with age, concomitant alcohol consumption, existing liver disease, and during the immediate postpartum period. Regular check-ins, lab monitoring when indicated, prompt recognition of symptoms, and sensible lifestyle choices (no alcohol) significantly reduce risk during therapy.

Isoniazid dosing for adults and children

 Dosing depends on whether therapy is for latent infection or active disease, as well as on age and body weight. For adults with LTBI receiving daily isoniazid monotherapy, 300 mg by mouth once daily is commonly used for 6 or 9 months. For intermittent regimens under supervision (for example, 900 mg once weekly when combined with rifapentine in the 3HP regimen), dosing follows standardized protocols. For treatment of active TB disease, adults often receive 5 mg/kg (maximum 300 mg) once daily when isoniazid is part of a multi-drug regimen, with intermittent dosing options available in certain DOT settings per guideline.

In pediatrics, typical daily dosing is 10–15 mg/kg (up to 300 mg) once daily, with alternative intermittent schedules determined by the child’s clinician and programmatic guidelines. Because pediatric dosing is weight-based and requires growth monitoring and careful adherence support, families should remain in close contact with their pediatric provider and local health department to ensure the regimen remains optimal as the child grows.

LTBI regimens (6H/9H/3HP/3HR)

 Several guideline-endorsed options exist for latent TB infection in the USA. Daily isoniazid for 6 months (6H) or 9 months (9H) is well-established and effective. Shorter-course regimens may improve completion rates, including 3HP (isoniazid plus rifapentine weekly for 12 doses) and 3HR (daily isoniazid plus rifampin for 3 months). Your clinician will assess potential drug interactions, pregnancy status, HIV therapy, and other clinical variables to decide on the most suitable plan.

Factors your provider considers when choosing a regimen include past TB exposure history, age, risk of hepatotoxicity, potential interactions (for example, between rifamycins and antiretroviral therapy), and preferences about treatment duration. In any regimen, consistent adherence is essential to ensure TB prevention is achieved. If you experience side effects, contact your provider early—simple adjustments or supportive care often allow you to stay on track safely.

• Short-course options (e.g., 3HP, 3HR) are often preferred in U.S. practice due to higher completion rates.
• Daily 6H or 9H remains appropriate for many patients when interactions or other factors limit the use of rifamycins.
• People with higher risk for progression to disease (recent contacts, immunocompromised individuals) should be prioritized for prompt initiation and adherence support.

Missed doses and adherence (DOT)

If you miss a dose, take it as soon as you remember—unless it is nearly time for your next dose. In that case, skip the missed dose and resume your regular schedule. Do not take two doses at once. Because adherence is crucial for success, many U.S. programs use directly observed therapy (DOT) or digital adherence technologies for some regimens, especially during active TB disease. DOT involves a healthcare worker observing medication ingestion, either in person or via secure video, to ensure consistency and to provide real-time support. If you anticipate challenges, talk to your care team proactively; they can set up reminders, coordinate refill synchronization, and schedule check-ins to help you complete therapy.

Food, alcohol, and dietary considerations

Labeling recommends taking isoniazid on an empty stomach—at least 1 hour before or 2 hours after meals—since food, particularly high-fat meals, can reduce absorption and delay peak concentrations. If stomach upset occurs, your clinician may allow taking it with a light snack to improve tolerability while maintaining effectiveness. Avoid alcohol entirely; combining alcohol with isoniazid increases the risk of liver injury. Some people may experience flushing, palpitations, or headaches after consuming foods high in tyramine (e.g., certain aged cheeses, cured meats) or histamine (e.g., some fish), though these reactions are uncommon. Ask your pharmacist for diet-specific guidance tailored to your regimen and medical history.

How to take isoniazid properly

 Take isoniazid exactly as prescribed, at the same time each day when on daily therapy, and avoid skipping doses. Swallow tablets with a full glass of water. Keeping a medication diary or using a smartphone reminder can be helpful. Before you start, review all prescription and over-the-counter medicines and supplements with your clinician and pharmacist, and inform them promptly of any changes. This comprehensive review helps identify and prevent drug interactions, ensures that vitamin B6 is dosed appropriately when indicated, and supports a safe, effective course of therapy from start to finish.

If you are on a combination regimen for active TB, follow the instructions for each medicine carefully; the schedule may include multiple agents with distinct administration guidance. Do not stop therapy early even if you feel better—stopping too soon can lead to treatment failure and drug resistance. If side effects occur, your provider may adjust doses, modify the regimen, or provide supportive measures so you can stay on track safely.

Pregnancy and breastfeeding

Pregnancy is not an absolute contraindication to isoniazid. In the USA, clinicians often recommend vitamin B6 supplementation during pregnancy to lower neuropathy risk and carefully monitor liver function, especially in the immediate postpartum period, when the risk of hepatotoxicity can be higher. The decision to treat LTBI during pregnancy depends on individual risk factors; some people may defer LTBI therapy until after delivery if the risk of progression to active disease is low. For active TB disease, treatment during pregnancy is essential to protect both the pregnant person and the baby.

Isoniazid is excreted into breast milk in small amounts. Breastfeeding is generally considered compatible with isoniazid therapy. Pediatric specialists may recommend vitamin B6 supplementation for the breastfeeding individual and, when the infant is also taking isoniazid, appropriate pediatric dosing. Discuss your breastfeeding plans with your healthcare team so they can tailor monitoring and supplementation to your needs.

Pharmacist’s tips for taking isoniazid

 Take isoniazid on an empty stomach for best absorption unless your clinician advises otherwise due to stomach upset. Do not drink alcohol while on therapy. Use a pill organizer or smartphone reminders to maintain daily consistency. If you are traveling across time zones, ask your pharmacist for a plan to keep dosing on schedule.

Keep a current list of all medications, including herbal supplements and vitamins, and share it at every healthcare visit. Isoniazid can interact with several medicines (for example, certain anti-seizure drugs and warfarin), so a thorough review helps prevent problems. Alert your clinicians promptly if you notice symptoms such as persistent nausea, vomiting, abdominal pain, unusual fatigue, dark urine, yellowing of skin or eyes, unusual tingling or numbness, or mood changes.

Attend scheduled follow-ups. Some patients require baseline and periodic lab tests, particularly those with liver disease, older adults, people who use alcohol, or those in the immediate postpartum period. Timely monitoring helps keep therapy safe while achieving the goal of TB prevention or cure.

If a dose is missed, take it when remembered unless it is close to the next scheduled time—never double up. If you experience side effects, do not stop the medication on your own; instead, contact your provider for guidance. Most issues can be managed while maintaining effective TB therapy.

Safety Precautions

 Do not take isoniazid if you have known hypersensitivity to the drug or if your clinician has advised against it due to prior severe adverse reactions. Use caution if you have existing liver disease, drink alcohol, or are in the immediate postpartum period. Avoid alcohol during treatment to minimize the risk of liver injury.

Notify your care team about all medical conditions, including HIV, diabetes, chronic kidney disease, seizure disorders, mental health conditions, malnutrition, or peripheral neuropathy. These factors may influence whether pyridoxine supplementation is recommended, how often you should be monitored, and which TB regimen is chosen. Report new symptoms promptly and keep all follow-up appointments to support safe, successful treatment.

Isoniazid side effects

 Many people take isoniazid without significant problems, but side effects can occur. The most important to recognize early are signs of liver irritation (hepatotoxicity) and signs of peripheral neuropathy. Hepatotoxicity may present with fatigue, weakness, nausea, vomiting, anorexia, upper abdominal pain, dark urine, or jaundice. Peripheral neuropathy typically manifests as tingling, burning, or numbness in the hands or feet; vitamin B6 supplementation can reduce this risk in vulnerable groups.

Other possible effects include rash, pruritus, fever, mild elevations in liver enzymes, hematologic changes (such as anemia), mood or sleep changes, and rare lupus-like reactions. Central nervous system effects (such as seizures) are uncommon but can occur, especially at higher serum levels or in people with predisposing factors. Promptly contact your clinician if you notice any concerning symptoms; early evaluation helps prevent progression and allows tailored management.

Your provider will review the signs and symptoms to watch for at the start of therapy and advise you on when to seek urgent care. In general, severe or persistent symptoms—particularly those suggestive of liver injury—warrant immediate medical evaluation and, in some cases, temporary discontinuation of therapy while the cause is investigated.

Adverse effects can vary based on age, coexisting conditions, concurrent medications, alcohol use, and the specific TB regimen. Communication with your healthcare team is critical to navigate side effects while staying on the path to cure or prevention.

Adverse effects by system

Hepatic and gastrointestinal effects may include:

• loss of appetite, upper abdominal discomfort, nausea, vomiting, or changes in bowel habits
• transient or persistent elevations in liver enzymes
• dark urine or jaundice (yellowing of skin or eyes)
• generalized weakness or fatigue related to hepatic irritation
• dyspepsia or epigastric pain, sometimes improved by adjusting timing with a light snack
• rare cholestatic patterns of liver injury requiring prompt evaluation
• very rare severe hepatitis; seek urgent care if symptoms appear

Neurologic and psychiatric effects can include:

• tingling, burning, or numbness in hands/feet (peripheral neuropathy)
• headache or dizziness
• sleep disturbances or unusual dreams
• mood changes, irritability, or, rarely, psychosis (seek medical advice)
• seizures in susceptible individuals or with elevated serum levels
• vision changes should prompt evaluation for other causes in the regimen
• faintness or low blood pressure are uncommon; report persistent symptoms

Dermatologic and general symptoms may include:

• mild rash or pruritus, typically transient

Hypersensitivity and immune-mediated reactions can include:

• fever, rash, lymph node swelling, arthralgias, or lupus-like syndromes
• hematologic changes (for example, anemia)
• rare severe skin reactions; seek urgent care for extensive rash or mucosal involvement
• swelling of extremities; report promptly if persistent
• palpitations or rapid heartbeat (evaluate alternative causes as well)
• fatigue or headaches; discuss with your clinician if ongoing
• respiratory symptoms (such as cough) are usually related to TB itself; report significant changes

Reporting side effects

 If you experience any side effects, contact your clinician or pharmacist right away. In the USA, you may also report adverse events to the FDA’s MedWatch program. Rapid reporting allows timely evaluation, dose adjustments, or regimen modifications when necessary to keep you safe and on course for TB prevention or cure.

Isoniazid interactions with other medicines

 Isoniazid can interact with prescription and over-the-counter drugs and supplements. Always inform your healthcare team about everything you take. Notable interactions include increased serum levels and effects of certain anti-seizure medicines (such as phenytoin and carbamazepine) and enhanced anticoagulant effect of warfarin. Concomitant use with disulfiram can precipitate neuropsychiatric reactions. Alcohol significantly increases the risk of hepatotoxicity and should be avoided. Rifampin and other rifamycins used in TB regimens have their own interaction profiles and can affect overall therapy planning, so your clinician will coordinate all agents carefully.

Some medicines that may interact with isoniazid include:

• phenytoin, carbamazepine (monitor levels and signs of toxicity)
• valproic acid (monitor for increased effects)
• warfarin (INR may increase; dose adjustments and closer monitoring may be required)
• disulfiram (risk of neuropsychiatric reactions)
• alcohol (avoid; hepatotoxicity risk increases)

This list is not exhaustive. Keep a written or electronic list of all your medications and share it at every visit. Your pharmacy team can help identify potential problems early and coordinate with your prescriber to keep your regimen safe and effective.

Recommendations from our specialists

 If you have a positive TB test or a known exposure, do not wait—schedule an appointment with a U.S. healthcare provider to confirm your diagnosis and start the most appropriate regimen. Isoniazid remains a proven, cost-effective option for both latent and active TB (in combination), but it must be used under medical supervision with attention to liver safety, vitamin B6 supplementation when indicated, and medication interactions. Our team emphasizes practical adherence strategies—such as reminders, synchronization of refills, and DOT or video-DOT where available—so you complete therapy with confidence. With coordinated care and consistent follow-up, most people tolerate isoniazid well and achieve excellent outcomes.

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