in both TB and HIV then outcomes are not compromised for either disease. If HIV treatment has to be started while a patient is still on TB treatment, then the advice of a specialist HIV pharmacist should be sought. In general, there is no significant interactions with the NRTI's. Nevirapine should not be used with rifampicin. Efavirenz may be used, but dose used depends on the patient's weight (600 mg daily if weight less than 50 kg; 800 mg daily if weight greater than 50 kg). Efavirenz levels should be checked early after starting treatment (unfortunately, this is not a service routinely offered in the US, but is readily available in the UK). The protease inhibitors should be avoided if at all possible: patients on rifamycins and protease inhibitors have an increased risk of treatment failure or relapse. The World Health Organization (WHO) warns against using thioacetazone in patients with HIV, because of the 23% risk of potentially fatal exfoliative dermatitis. According to Caprisa 003 (SAPiT) Study the mortality in patients who were started on anti-retrovirals during TB treatment was 56% lower than those started after TB treatment was completed (hazard ratio 0.44 (95% CI: 0.25 to 0.79); p=0.003). Epilepsy INH may be associated with an increased risk of seizures. Pyridoxine 10 mg daily should be given to all epileptics taking INH. There is no evidence that INH causes seizures in patients who are not epileptic. TB treatment involves numerous drug interactions with anti-epileptic drugs and serum drug levels should be closely monitored. There are serious interactions between rifampicin and carbamazepine, rifampicin and phenytoin, and rifampicin and sodium valproate. The advice of a pharmacist should always be sought. Covid- 19 TB and COVID-19 are a "cursed duet" and need immediate attention. TB should be considered a risk factor for severe COVID disease and patients with TB should be prioritised for COVID-19 preventative efforts, including vaccination. Drug-resistance Definitions Multi-drug resistant tuberculosis (MDR-TB) is defined as TB that is resistant at least to INH and RMP. Isolates that are multi-resistant to any other combination of anti-TB drugs but not to INH and RMP are not classed as MDR-TB. As of October 2006, "Extensively drug-resistant tuberculosis" (XDR-TB) is defined as MDR-TB that is resistant to quinolones and also to any one of kanamycin, capreomycin, or amikacin. The old case definition of XDR-TB is MDR-TB that is also resistant to three or more of