Common Peripheral neuropathy (tingling and numbness of feet and hand), Increased liver enzymes, Hepatitis (viral infection of liver), Jaundice.

Expert advice for Isoniazid
Take it on an empty stomach (if it upsets your stomach, take it with food). Take it as and when prescribed (in case you skip a dose, do not take two doses at one time). In order to kill the TB bacteria and cure the disease completely, you will have to take this medicine for 6 to 12 months (your doctor will the precise duration for which you will take the medicine). You need to take vitamin B6 (Pyridoxine) along with Isoniazid. Vitamin B6 (Pyridoxine) will prevent possible numbness and tingling fingers and toes that may be caused by Isoniazid.

Q. Is Isoniazid an antibiotic?
Isoniazid is an antibiotic used in the prevention and treatment of tuberculosis or TB (a serious infection caused by bacteria that affects the lungs and in certain cases other parts of the body)

Q. Is Isoniazid chemotherapy/chemotherapy drug?
Isoniazid is a primary antibiotic used for treatment of tuberculosis. Do not confuse it with chemotherapy or chemo drugs used for the treatment of cancer

Q. Is Isoniazid bacteriostatic or bactericidal?
Isoniazid is a bacteriostatic antibiotic. It stops or suppresses growth of tuberculosis causing bacteria by interfering with the formation of protective outer covering (cell wall) which is essential for their growth

Q. Is Isoniazid safe?
Yes. Isoniazid is safe if used at prescribed doses for the prescribed duration as advised by your doctor

Q. Is Isoniazid a MAOI?
Isoniazid has very weak inhibitory activity on enzymes monoamine oxidases (MAO); however it is not used as a monoamine oxidase inhibitor (MAOI)

Q. Is Isoniazid a sulfa drug?
No. The chemical structure and mechanism of action of Isoniazid is different from sulfa drugs

Q. Is Isoniazid an inducer or inhibitor?
Isoniazid is an inhibitor (decreases activity) of an important liver enzyme system that is responsible for the final processing and elimination of several drugs from the body

Q. Can I take isoniazid with ibuprofen/Benadryl/Nyquil/Aleve/Mucinex/amoxicillin?
There no known serious drug interactions of isoniazid with ibuprofen, paracetamol (trade name: Tylenol), naproxen (trade name: Aleve), amoxicillin or any active drug present in Nyquil or Mucinex. Please inform your doctor about all the medication you are currently taking to avoid interactions that may reduce effectiveness of any treatment or aggravate side effects

Q. Does Isoniazid cause weight loss/weight gain/hair loss/diarrhea/affect menstruation?
Changes in body weight (gain/loss), hair loss, diarrhea or changes in menstruation are not among the known side effects of Isoniazid. You may experience few of these side effects while on multi drug (including Isoniazid) treatment for tuberculosis

Q. Does Isoniazid cause acne/make you tired/cause constipation?
You may experience unusual tiredness, constipation or acne while on treatment with Isoniazid. Please inform your doctor about all the medication you are currently taking to avoid interactions that may reduce effectiveness of any treatment or aggravate side effects

Q. Does Isoniazid affect birth control?
Isoniazid has no known interaction with commonly used oral contraceptives (birth control pills). However, multidrug treatment for tuberculosis contains active drug rifampin that decreases the effectiveness of oral contraceptives and hampers birth control.