The present study was conducted to investigate the impact of diphenhydramine hydrochloride on the ability to initiate sleep.

Diphenhydramine hydrochloride (herein referred to as diphenhydramine) is an antihistamine of the ethanolamine classes with known sleep-inducing properties and is approved by the Food & Drug Administration to reduce the time to sleep onset in individuals having difficulty falling asleep. The goal of the study is to investigate diphenhydramine versus placebo with regard to several sleep parameters, including time to sleep onset, in healthy adult subjects suffering from occasional sleeplessness.

Inclusion Criteria:

• be male or female subjects, ≥18 years of age to 55 years of age, who report that they are currently experiencing occasional sleeplessness characterized by difficulty initiating sleep (ie, taking ≥30 minutes to fall asleep) on average 2-4 times per week for less than 1 month;
• be in good general health without clinically significant disease (no previously diagnosed sleep disorders);
• if female, have a negative screening pregnancy test and agree to be on approved methods of birth control throughout the study

Exclusion Criteria:

• have a clinically significant illness within 30 days of Screening;
• are taking medication that could interfere with the study medication;
• have been under a clinician's care for insomnia treatment and control within the past year or has a history of insomnia or is currently taking prescription medications for insomnia;
• are currently taking medications known to effect sleep function;
• have current or past history of serious, severe or unstable physical or psychiatric illness;
• have current diagnosis of severe urinary retention;
• have current diagnosis of untreated narrow angle glaucoma;
• had participated in a clinical drug study or used an investigational new drug during the previous 30 days;
• have any clinically significant or abnormal finding in physical examination, vital signs, ECG, or clinical laboratory tests that may affect the subject's safety or outcome of the study;

After informed consent but prior to 1st dose of study drug, only SAEs were collected in the eCRFs (the study had no SAEs). After a patient received his/her first dose of investigational product until his/her exit from the study, all AEs were collected.