Varenicline and Accelerated Transcranial Magnetic Stimulation (TMS) for Quitting Nicotine Use (Pilot Study)

The goal of this clinical trial is to learn if a combination of varenicline and enhanced accelerated Transcranial Magnetic Stimulation (aTMS) works to help adults quit using nicotine products. Researchers will compare varenicline + active aTMS with a single dose of D-Clycloserine to varenicline + sham (inactive) aTMS with a placebo pill to see the effect of enhanced aTMS on reaching abstinence. The main question it aims to answer is: Does receiving active enhanced aTMS + varenicline lead to higher abstinence rates and lower nicotine craving? Participants will be asked to: * Complete 2 brain MRI scans * Take varenicline every day for 12 weeks * Quit using nicotine products at the end of the second week of varenicline * Complete one day of up to 20 TMS treatments * Take a single dose of D-Cycloserine medication on the day of TMS treatment * Complete 12 brief, weekly follow-up visits * Complete a brief daily survey each day that they take the study drug

Inclusion Criteria: * Age ≥ 18 and ≤65; * The ability to give written, informed consent; * Fluency in English; * Reported interest in quitting nicotine vaping or smoking within the next month; * Nicotine dependence, as defined by a score of ≥4 on the 10-question E-cigarette Dependence Inventory (ECDI) or Fagerström Test for Nicotine Dependence (FTND); * Smoke or vape nicotine daily for at least the past 90 days, as confirmed by self-report and timeline follow-back methods; * Saliva cotinine \>30ng/mL; Exclusion Criteria: * Pregnancy or breastfeeding; * Use of smoking cessation pharmacotherapy in the past month; * Unwilling to abstain during the study from using smoking cessation aids other than those provided by the study; * Prior adverse drug reaction to varenicline; * Contraindication to D-Cycloserine (including allergy to D-Cycloserine, significant renal impairment or known kidney disease, pregnancy) * Receiving or planning to receive other TMS treatments or investigational drugs during course of participation * Contraindications to TMS (including seizures, metallic implants, severe existing tinnitus, etc.); * Contraindications to MRI (including presence of a cardiac pacemaker or pacemaker wires, metallic particles in the body, vascular clips in the head or previous neurosurgery, prosthetic heart valves, claustrophobia); * Inpatient psychiatric hospitalization or suicide attempts in the past six months, or recent active suicidal ideation or suicidal behavior identified at enrollment or baseline visits; * History of seizures and/or history of TBI subtypes associated with elevated seizure risk (e.g. penetrating injury and intraparenchymal hemorrhage) * History of unstable neurological illness or major medical illness, such as epilepsy or renal impairment, in the past six months, unless clearly resolved; * In the opinion of the investigators, evidence of active problem substance use severe enough to compromise ability to safely participate; * In the opinion of the investigators, unable to safely participate in this study and/or provide reliable data (e.g., claustrophobia, unable to tolerate TMS or MRI procedures, etc.).