Antitubercular any agent or group of drugs used to treat tuberculosis. Antitubercular includes cycloserine, ethambutol, ethionamide, isoniazid, pyrazinamide, rifampicin, and streptomycin. Action uses, dosage, and side effect of all these drugs are also covered in this chapter. Common side effects are optic neuritis, headache, abdominal pain, and GI upset. Serious side effects include hepatitis and thrombocytopenia. Rifampicin is used to treatment of active tuberculosis. Streptomycin is used to treatment of active tuberculosis, enterococcal endocarditis, and plague.