Specific Aim: To investigate if isotretinoin (13-cis-retinoic acid) administration decreases CYP2D6 activity in adolescent patients.

In this aim, we will conduct a drug-drug interaction study evaluating the effects of 13-cis-retinoic acid on non-induced CYP2D6 activity in adolescent patients. Secondary analysis will evaluate the relationship between retinoid concentrations and CYP2D6 activity in these special populations

Inclusion Criteria:

• Non-pregnant
• ≥ 12 years
• Patients with severe acne that are expected to receive isotretinoin for therapeutic reasons

Exclusion Criteria:

• Weight < 80 lbs
• Allergy or adverse reaction to dextromethorphan, vitamin A or isotretinoin
• Pregnant or planning to become pregnant
• Unable to follow isotretinoin risk evaluation and mitigation strategies (REMS) program (also known as iPLEDGE program)
• Chronic or persistent cough accompanying asthma, smoking or chronic obstructive pulmonary disease,
• Productive cough,
• Fever,
• Known kidney disease,
• Known liver disease,
• Diabetes
• Obesity, body mass index ≥ 30 kg/m2
• Bipolar disease,
• Attention deficit disorder,
• Social phobia,
• Concurrent or use within 14 days of drugs known to interact with dextromethorphan or cytochrome P450 2D6 (CYP2D6) or drugs known to increase the risk of adverse effects from dextromethorphan
• Concurrent use of any other product containing dextromethorphan
• Consuming foods, beverages or dietary supplements known to interact with dextromethorphan or CYP2D6
• Unable to give written informed consent/assent,
• Inability to fast for 4 hours prior to study.
• Wards of the State

After completion of the study, we plan to follow NIGMS/NIH and University of Washington requirements for data sharing.

All subjects that completed the study.

1 week to 6 months