sentences:  If it is difficult finding five drugs to treat then the clinician can request that high-level INH-resistance be looked for.If the strain has only low-level INH-resistance (resistance at 0.2 mg/l INH, but sensitive at 1.0 mg/l INH), then high dose INH can be used as part of the regimen.When counting drugs, PZA and interferon count as zero; that is to say, when adding PZA to a four-drug regimen, another drug must be chosen to make five.