The proposed study represents a crucial and important stage in translating basic research to strategies for treating nicotine dependence. The investigation addresses an important public health issue by testing an intervention - informed by basic research - that may lead to a more effective and efficient treatment for smokers. The expected findings should provide initial effect size data for the addition of isradipine to an integrated psychosocial/behavioral and pharmacological smoking cessation intervention for smokers, and thus provide the necessary data for a large-scale follow-up trial.

The current protocol will apply a pharmacologic augmentation strategy informed by basic research in animal models of addiction. Our goal is to evaluate the enhancing effect of isradipine, an FDA-approved calcium channel blocker, on the extinction of craving-a key mechanism of drug relapse after periods of abstinence. To activate craving robustly in human participants, we will use multimodal smoking cues including novel 360° video environments developed for this project and delivered through consumer virtual reality headsets. Adult smokers will take either isradipine or placebo and complete the cue exposure protocol in a double-blind randomized control trial. In order to test the hypothesis that isradipine will enhance retention of craving extinction, participants will repeat cue exposure in a medication-free state 24 h later. The study will be implemented in a primary care setting where adult smokers receive healthcare, and smoking behavior will be tracked throughout the trial with ecological momentary assessment.

Inclusion Criteria:

1. 18-65 years old;
2. Willing and able to provide informed consent, attend all study visits, and comply with the protocol;
3. Daily smoker for at least one year; and
4. Currently smoke an average of at least 5 cigarettes per day.

Exclusion Criteria:

1. Current diagnosis of a psychotic, eating, developmental or bipolar disorder, or significant suicide risk;
2. Current treatment for smoking cessation or use of other nicotine products, including e-cigarettes;
3. Exclusion criteria related to isradipine administration: (a) known allergy or sensitivity to isradipine, (b) hypertension, (c) congestive heart failure, (d) any type of liver disease, (e) current pregnancy, (f) women of childbearing potential who are not using medically accepted forms of contraception, (g) current use of Rifampin, which decreases the availability of calcium channel blockers, or of Tagamet, which can increase hypotensive effects and inhibit hepatic metabolism of isradipine, (h) any other significant medical condition that increases risk, as determined by the study physician;
4. Significant vision problems that would prevent engagement with the 360° video environment; and
5. Past six month substance use disorder, other than nicotine use disorder, assessed by structured interview.

Protocol files are available on the The Open Science Framework page for this project

Supporting information will be added as it becomes available.

Available files are stored on the The Open Science Framework page for this project.

48 hours

Adverse events were collected during session 1 and session 2.

Study capsules will be prepared containing: (a) 15 mg immediate release isradipine or (b) pill placebo consisting of Avicel microcrystalline cellulose powder (non-digestible pass-through). Isradipine and placebo capsules will be identical in appearance to maintain the double-blind. Individual doses will be dispensed to participants by blinded personnel 75 m prior to the first cue exposure session and patients will be asked to remain in the clinic until session time.