Background: Radiotherapy appears to be one of the most effective therapies in head and neck tumors, however, there are a lot of complications related to it. Oral Mucositis is one of the most common complications following radiotherapy. There are currently huge unmet needs for management of oral mucositis. It causes severe pain, reduces food intake and affects quality of life of the head and neck cancer patients .N-acetylcysteine (NAC) is a glutathione precursor which has an antioxidant property and protects against radiation therapy-induced free radical damage. NAC reduces the production of inflammatory markers which leads to decrease inflammation, treats oral mucositis and enhances quality of life of the patient. Aim: To evaluate the effectiveness of N-acetylcysteine and its formulated nanoparticles in treatment of radiotherapy induced oral mucositis in oral cancer patients .

Inclusion Criteria:

• Patients diagnosed with oral cancer by incisional biopsy histological examination.
• Patients above the age of 20 years.
• Patients receiving radiotherapy either as postoperatory (adjuvant) or as a definitive therapy in the treatment for oral cancer.
• Patients with radiotherapy induced-oral mucositis.
• Radiation dose ≥ 60 Gy which is responsible for oral mucositis development in oral cancer patients.

Exclusion Criteria:

• Patients diagnosed with any other type of cancer.
• Patients with any systemic disease as diabetes, cardiovascular, liver disorders and kidney disorders.
• Patients under anticoagulants such as warfarin, heparin or aspirin.
• Patients with findings of any physical or mental abnormalities