Determine bioequivalence, safety and tolerability of guaifenesin extended-release 600 mg (Mucinex® SE) compared to an immediate-release syrup reference product in normal healthy subjects.

Inclusion Criteria:

1. Males and/or females between the ages of 19 and 55 years, inclusive.

2. Females of childbearing potential must be using one of the following acceptable birth control methods:

   1. Intra-uterine device in place for at least 3 months prior to Day 1 of Period 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 (e.g., oral, depo injection, transdermal patch, or vaginal ring) for at least 3 months prior to Day 1 of Period 1 through 30 days beyond completion of study;

   Abstinence is not an acceptable form of contraception; however, abstinent female subjects may be admitted to the study if they agree, and have signed a statement to the effect, that upon becoming sexually active, will use a condom with spermicide from screening through 30 days beyond completion of the study.

3. Females of non-childbearing potential should be surgically sterile (bilateral tubal ligation with surgery at least 6 months prior to study or hysterectomy and/or bilateral oophorectomy at least 3 months prior to Day 1 of Period 1) or postmenopausal >2 years prior to Day 1 of Period 1. A follicle stimulating hormone (FSH) concentration >40 miU/mL must be obtained and recorded for any postmenopausal females.

4. Good general health as determined by the Principal Investigator's (PI) review of medical history, physical examination, vital sign measurements, electrocardiogram (ECG), and clinical laboratory measures.

5. Body weight between 50 - 100 kg and body mass index (BMI) within 18 - 30 kg/m2.

6. Non-tobacco users, who have not used nicotine or nicotine-containing products for at least 365 days prior to Day 1 of Period 1.

7. Able to read, understand and sign the informed consent after the nature of the study has been explained.

8. Negative urine screen for drugs of abuse and alcohol at screening and each check in.

9. If female, negative finding on serum pregnancy test at screening and each check-in.

10. Non alcohol or drug abuser - non alcohol abuse is defined as history of less than 4 drinks daily. A drink 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).

Exclusion Criteria:

1. Clinically significant abnormalities detected by medical history, physical examination, vial sign measurements, ECG, or clinical laboratory findings (as determined by the PI/designee) including a hemoglobin value <12 gm/dL at screening. If a subject's hemoglobin drops below 11.0 gm/dL during the study, the subject may be dropped from the study at the discretion of the PI.
2. Any disease or condition, which could impact absorption, distribution, metabolism, or elimination of the study drugs (as determined by the PI/designee).
3. Females who are pregnant or nursing.
4. History of sensitivity reaction to guaifenesin.
5. Receipt of an investigational drug within 30 days prior to Day 1 of Period 1.
6. Abnormal diet (for whatever reason) during the 30 days prior to Day 1 of Period 1.
7. Donation of blood or significant loss of blood within 56 days or plasma within 14 days prior to Day 1 of Period 1.
8. Known or suspected use of illicit drugs.
9. The use of any medication (with the exception of hormonal contraceptives for women of childbearing potential) for 14 days or 5 half-lives of the drug (whichever is longer) prior to Day 1 of Period 1.
10. Test positive for Hepatitis B surface antigen, Hepatitis C antibodies, or HIV at Screening.

Up to Day 17