Inclusion Criteria:

• * Healthy on the basis of medical history and limited physical examination.
• * Current regular user of E-Cigarettes (≥ 15 days in the past 30 days)

Exclusion Criteria:

• * • Medications
• * Use of medications that are inducers of nicotine metabolizing enzyme CYP2A6 (Example: rifampicin, carbamazepine, phenobarbital, and other anticonvulsant drugs).
• * Use of sympatholytic medications for cardiovascular conditions including hypertension (Example: beta and alpha-blockers).
• * Concurrent use of nicotine-containing medications (Example: nicotine patch, lozenge, gum).
• * Any stimulant medications (example: Adderall) generally given for ADHD treatment.
• • Pregnancy
• * Pregnancy (self-reported and urine pregnancy test)
• * Breastfeeding (determined by self-report)
• * Women of childbearing potential must be using an acceptable method of contraception
• * Inability to read and write in English
• * A known propylene glycol/vegetable glycerin allergy
• * Uncomfortable with getting blood drawn