The purpose of this study is testing the use of topical Imipramine in combination with topical photodynamic therapy's (PDT) effect on pain following treatment. PDT is a commonly used treatment in dermatology for patients who have many pre-cancers (actinic keratosis-AKs) on their skin. These are both FDA-approved treatments, but this study is evaluating their use in combination, which has not been evaluated in the past. The investigators have been doing studies using animals that suggest that imipramine might make the PDT less painful and might help it work better. In order to participate, the subject and their dermatologist have decided that they would benefit from PDT to treat their skin due to many AK precancerous lesions. Please note that neither PDT nor imipramine are experimental treatments, but treating their skin with imipramine before PDT is a new approach.

Inclusion Criteria:

• Male or female ages 18 and older
• Skin type must be "Fair", Fitzpatrick type I to III, due to the presence of actinic damage in this population.
• Subjects need to have a physician's order to receive PDT treatment on their face, scalp or forearms.
• Willing to participate and understand the informed consent document.
• Willing to avoid excess sun exposure/tanning beds to the area to be treated with PDT.

Exclusion Criteria:

• Those currently taking any tricyclic antidepressants (TCAs)
• Those currently taking any selective serotonin reuptake inhibitor (SSRI)
• Those with porphyria
• Large tattoos in the treated areas
• Pregnancy or nursing
• Taking any oral or topical medications that could interfere with the PDT (Appendix A)
• Active rashes in the area