Study to Evaluate the Pharmacokinetics of Mucinex® 1200 mg Extended-Release Tablet

Inclusion Criteria: 1. Males and females ≥19 to 55 years of age inclusive. All females who were of childbearing potential must have been using one of the following acceptable birth control methods for the time periods specified: 1. Intrauterine device (IUD) in place for at least 3 months prior to Day 1 through 30 days beyond study completion. 2. Barrier method (condom or diaphragm) with spermicide for at least 7 days prior to screening through 30 days beyond study completion. 3. Stable hormonal contraceptive (oral, depo injection, transdermal patch, or vaginal ring) for at least 3 months prior to Day 1 through 30 days beyond completion of study. Note: Abstinence (sexually inactive) was not an acceptable form of contraception; however, abstinent female subjects could have been admitted to the study if they had reported being abstinent at least 14 days prior to screening and they agreed, and signed an "Abstinence Statement" to the effect, that upon becoming sexually active, they would use a condom with spermicide from that time through 30 days beyond completion of the study. Females of non-childbearing potential must have been surgically sterile (bilateral tubal ligation with surgery at least 6 months prior to Day 1 or hysterectomy and/or bilateral oophorectomy at least 3 months prior to Day 1 or post-menopausal ≥2 years prior to Day 1). A follicle stimulating hormone level (FSH) \>40 mIU/mL must have been obtained and in the record for any post-menopausal female. 2. Negative serum pregnancy test at Screening and at Check-in for all female subjects. 3. Good general health as determined by the PI's review of medical history, physical examination, 12-lead electrocardiogram (ECG), vital sign measurements (after 2 minutes resting in the seated position), and clinical laboratory measures. 4. Body mass index (BMI) of 19 to 29 kg/m2, inclusive. (BMI = weight (kg)/\[height (m2)\]). 5. Non-tobacco users, who had not used nicotine or nicotine-containing products for at least 6 months prior to Day 1. 6. Negative finding on tests for Hepatitis B surface antigen (HBsAG), Hepatitis C virus (HCV) antibodies, human immunodeficiency virus (HIV). 7. Negative urine screen for drugs of abuse and alcohol at Screening and at Check-in. 8. Likely to be compliant with study requirements and complete the study, as determined by the Investigator. 9. Able to read, understand, and sign the informed consent after the nature of the study had been explained and had read, signed, and dated an Institutional Review Board (IRB)-approved informed consent form for subjects to participate in the study. Exclusion Criteria: 1. Clinically significant abnormalities detected by medical history, physical examination, vital sign measurements, ECG findings, or clinical laboratory findings (as determined by the PI). If the subject's hemoglobin dropped below 11.0 gm/dL during the study, the subject may have been dropped from the study at the discretion of the PI/designee. 2. Any disease or condition, which could impact absorption, distribution, metabolism, or elimination of the study drug (as determined by the PI/designee). 3. Females who were pregnant or nursing. 4. History of hypersensitivity reaction to guaifenesin. 5. Receipt of an investigational drug within 30 days prior to Day 1. 6. Abnormal diet (for whatever reason) during the 30 days prior to Day 1. 7. Donation of blood or significant loss of blood within 56 days prior to Day 1. 8. Donation of plasma within 14 days prior to Day 1. 9. Known or suspected use of illicit drugs (i.e., opiates, barbiturates, marijuana, et. al.). 10. The use of any medication, prescription or over-the-counter (OTC) (including herbal supplements) within the 14 days or 5 half-lives of the drug (whichever was longer) prior to Day 1 (with the exception of hormonal contraceptives for women of child-bearing potential). 11. Alcoholism or medicinal product or drug abuse within the past two years or excessive alcohol consumption (more than 10 units per week) \[one unit is defined as 5 ounces of wine, 12 ounces of beer, or 1.5 ounces of spirits (i.e., "hard" liquor such as gin, whiskey, or vodka, et. al.)\]. The subject was not to experience tolerance, withdrawal, compulsive use, or substance related problems such as medical complications, disruption in social and family relationships, vocational or financial difficulties, or legal problems. 12. Consumption of grapefruit, pummelo, Seville orange, or grapefruit juice within 14 days prior to dosing on Day 1 through study completion. 13. Consumption of alcohol within the 48 hours prior to dosing on Day 1. 14. Persons involved directly with the conduct of this study (i.e., Investigator, Sub-Investigators, Study Coordinators, etc.) or employees of Reckitt Benckiser and their families.