The primary purpose of the study is to evaluate the efficacy and safety of MELT-300 (Midazolam and Ketamine Sublingual Tablets) and the contribution of midazolam and ketamine components to sedation and during the surgery or ocular analgesia in participants undergoing cataract surgery with lens replacement.

This is a Phase 2, factorial-designed, randomized, double-blind, placebo-controlled, parallel-cohort study to be conducted in 324 adult male and female participants who are ≥ 55 years of age and undergoing cataract extraction with lens replacement. An additional 3 participants per site (first 3 participants enrolled per site) will be considered sentinel participants for the purpose of ensuring safety and that logistical and operational challenges that may occur during the study are identified and mitigated. Sentinel participants will be evaluated for safety but not for efficacy. The study aims to evaluate the efficacy and safety of MELT-300 and the contribution of midazolam and ketamine components for procedural sedation prior to cataract surgery. In the study, eligible study participants will be randomly assigned (1:1:1:1 ratio) to one of the following treatments: MELT-300 (3 mg/50 mg), midazolam 3 mg, ketamine 50 mg, and placebo sublingual tablet 30 (± 5) minutes prior to the anticipated start of surgery (defined as instillation of topical ocular anesthetic drops [i.e., proparacaine]) without food or water in the operating room. At the time of dosing, participants will be instructed to hold the tablet under their tongue until it is completely dissolved and to not swallow or chew the tablets. The study duration will be up to 35 days, including 28 days for screening and 7 ± 2 days after surgery.

Efficacy assessments will be performed after study medication administration before surgery, intraoperatively, and postoperatively on Day 1 (end of surgery defined as drape removal). Efficacy assessments will include assessments of sedation and intraoperative pain, the need for rescue medication for sedation or pain, and the ability to complete the surgery. Safety will be monitored at baseline, intraoperatively, postoperatively on Day 1, on the day after surgery (Day 2, via a phone call), and at 1 week (Day 8 ± 2 days) after dosing of study medication. Safety assessments will include monitoring of AEs, vital sign measurements, physical examinations, and 12-lead ECGs. Exploratory endpoints are postoperative pain as measured by the NPRS prior to discharge, 6 hours +/- 30 minutes after the end of surgery on Day 1 and on Days 2 (the day after surgery), the percentage of participants with concomitant medication opioid use, and average opioid consumption on Day 2 and participant likelihood of wanting study drug again for second cataract surgery as measured by an 11-point Likert scale on Day 2.

Inclusion Criteria:

1. Are to undergo unilateral primary uncomplicated CELR under topical anesthesia, with a phacoemulsification device and insertion of an intraocular lens.

Exclusion Criteria:

1. Participants scheduled for simultaneous bilateral or 2nd-eye cataract surgery (note, subjects scheduled for a future 2nd eye cataract study are eligible for the study).
2. Known sensitivity to benzodiazepines or ketamine.
3. Known sensitivity to -caines (including proparacaine), benzalkonium chloride (BAK).
4. Intraocular pressure (IOP) ≥ 23 mmHg in the study eye and/or ≥ 30 mmHg in the fellow eye at screening. This IOP exclusion requirement will only need to be re-confirmed on the day of surgery if it has been > 14 days since the screening visit.
5. History of iritis, or any ocular trauma with iris damage in the study eye.
6. Presence of active corneal pathology other than corneal pathology per slit lamp and an external eye exam at screening in either eye.
7. Presence of extraocular/intraocular inflammation in either eye.
8. Presence of active bacterial and/or viral infection in either eye.
9. History of intraocular non-laser surgery in the study eye within the 3 months prior to day of surgery, or intraocular laser surgery in the study eye within 30 days prior to the day of surgery.
10. Require or are planning other additional ocular surgery during the cataract surgery.

12. Have a history or clinical manifestations (e.g., signs, symptoms, laboratory values, diagnostic imaging, etc.) of significant gastrointestinal, cardiovascular, hepatic, renal, hematological, endocrine, neurological, psychiatric, respiratory, or other medical condition that in the opinion of the investigator might confound the study results or pose additional risk in administering the study procedures.

13. History of or presence of any connective tissue disorder (i.e., lupus, rheumatoid arthritis, fibromyalgia).

14. Use of disallowed medications, including the following:

1. Pain medication (opioids, non-steroidal anti-inflammatory drugs [NSAIDs], cyclooxygenase-2 [COX-2] inhibitors, tramadol, ketamine, clonidine, gabapentin, pregabalin, or cannabinoids) within 3 days prior to Day 1, or routine, daily opioid therapy within the past 30 days.

2. Central nervous system (CNS) active drugs such as benzodiazepines, tricyclic antidepressants, serotonin, and norepinephrine reuptake inhibitors (SNRIs), or selective serotonin reuptake inhibitors (SSRIs) for pain within 7 days prior to Day 1. These drugs are permitted for non-pain indications if the dose has been stable for at least 30 days prior to Day 1 and is planned to remain stable throughout the study. The use of lorazepam and other sleep medications, except those containing analgesic properties, is permitted.

3. Use of parenteral or oral corticosteroid(s) within 14 days prior to Day 1.

4. Antihypertensive agent or diabetic regimen at a dose that has not been stable for at least 30 days, or which is not expected to remain stable throughout the study.

   15. Chronic pain rated moderate to severe within the past week (4-pt categorical scale, 0=no pain, 1=mild pain, 2=moderate pain, 3=severe pain). 17. Hospital Depression and Anxiety Scale (HADS) score > 10