terizidone + cycloserine

Terizidone + cycloserine is a combination of two structurally related antibiotics used primarily in the treatment of multidrug-resistant tuberculosis (MDR-TB) and rifampicin-resistant tuberculosis (RR-TB). Terizidone is a prodrug composed of two molecules of cycloserine linked by terephthalaldehyde; it hydrolyzes in vivo to release cycloserine, which is the active agent. Both drugs act as bacteriostatic agents against Mycobacterium tuberculosis. Their mechanism involves competitive inhibition of enzymes critical for bacterial cell wall synthesis—specifically, alanine racemase and D-alanyl-D-alanine synthetase—thereby interfering with peptidoglycan formation. Cycloserine and terizidone are considered interchangeable in clinical practice, though some evidence suggests terizidone may be better tolerated, especially regarding neuropsychiatric adverse effects[1][2][4][6][8]. The combination is recommended by the World Health Organization as part of second-line regimens for MDR-TB/RR-TB[2]. Adverse effects include central nervous system toxicity such as seizures, depression, psychosis, peripheral neuropathy, and hypersensitivity reactions; pyridoxine supplementation is advised to mitigate neurotoxicity risk[3].