ORAL Midazolam is contraindicated with ritonavir as coadministration is likely to result in increased plasma concentrations of midazolam, thereby increasing the risk of extreme sedation and respiratory depression. Midazolam is extensively metabolised by CYP3A4. Co-administration with ritonavir may cause a large increase in the concentration of this benzodiazepine. No drug interaction study has been performed for the co-administration of ritonavir with benzodiazepines. Based on data for other CYP3A4 inhibitors, plasma concentrations of midazolam are expected to be significantly higher when midazolam is given orally. Therefore, ritonavir should not be co-administered with orally administered midazolam, whereas caution should be used with co-administration of ritonavir and PARENTERAL midazolam. Data from concomitant use of parenteral midazolam with other protease inhibitors suggest a possible 3–4 fold increase in midazolam plasma levels. If ritonavir is co-administered with parenteral midazolam, it should be done in an intensive care unit (ICU) or similar setting which ensures close clinical monitoring and appropriate medical management in case of respiratory depression and/or prolonged sedation. Dosage adjustment for midazolam should be considered, especially if more than a single dose of midazolam is administered.
Norvir Summary of Product Characteristics, AbbVie Ltd, September 2016.

ORAL midazolam is contraindicated with ritonavir due to potential for serious and/or life threatening reactions such as prolonged or increased sedation or respiratory depression. Concomitant use of PARENTERAL midazolam with ritonavir may increase plasma concentrations of midazolam. Coadministration [of PARENTERAL midazolam] should be done in a setting which ensures close clinical monitoring and appropriate medical management in case of respiratory depression and/or prolonged sedation. Dosage adjustment for midazolam should be considered, especially if more than a single dose of midazolam is administered.
Norvir Prescribing Information, AbbVie Inc, December 2016.