Study Evaluating the Pharmacokinetics of Doxylamine Succinate in Children

Inclusion Criteria: * are male or female children ages 2 to \< 18 years, with a minimum weight of 24 lbs and \> 5th percentile and \< 95th percentile for weight based on age and sex, at the time of dosing study medication * had a previous diagnosis of allergic rhinitis, or had a history of frequent upper respiratory infections (URI)/common cold and either be symptomatic, or at risk for future URI, including each of the following 3 criteria * Frequency Criterion: \> 6 infections per year for children aged 2 to \<6 years of age and \> 4 infections per year for children aged 6 to \< 18 years of age * Crowding Criterion: 4 persons living in the home or 3 persons sleeping in one bedroom * Exposure Criterion: another family member in the home who is ill with URI / common cold or a child in the family who is attending preschool or school with 6 children in the group. * are in good general health * are likely to be compliant and complete the study and have parent(s) or legally authorized representative(s) likely to be compliant and complete the study according to the Investigator * whose parent(s) or legally authorized representative(s) have signed and dated an Institutional Review Board (IRB)-approved consent form for the subject to participate in the study * must have signed an assent form as required by the site's IRB * if post-menarchal females, subjects must have a negative urine pregnancy test at screening and check-in, or serum pregnancy test at screening, if site required; * if post-menarchal females, subjects must practice abstinence or use an effective form of birth control (eg, intrauterine device, low dose oral contraceptives \[ 50g ethinyl estradiol\], contraceptive implants or injections, diaphragm with spermicide, cervical cap, or consort use of condom) for at least 3 months before being enrolled in the study. Exclusion Criteria: * has any history or presence of the following medical conditions: peptic ulcer, pyloroduodenal obstruction or other gastrointestinal disease; renal or hepatic disease; diabetes mellitus; hyperthyroidism; cardiovascular disease;increased ocular pressure or glaucoma; endocrine, metabolic, hematologic or neoplastic disease; seizure disorder; chronic respiratory diseases including asthma, emphysema and chronic bronchitis; autoimmune disease; immunodeficiency tuberculosis; bladder neck obstruction; significant dermatologic condition. * has a known sensitivity or allergy to doxylamine succinate * has a history of a severe allergic reaction to any drug or has multiple food/drug allergies * experienced febrile illness greater than 100°F within 7 days prior to dosing * reports any known enzyme-inducer, enzyme-inhibitor, or reported chronic exposure to enzyme-inducers such as paint solvents or pesticides within 30 days prior to dosing, unless approved by the Sponsor * reports any other prescription drug or herbal remedy usage within 14 days prior to dosing except for low dose contraceptives, unless approved by the Sponsor * reports any non-prescription drug or supplemental vitamin usage within 5 days prior to dosing * unwillingness to refrain from caffeine or other xanthine-containing beverages, including coffee and tea, alcohol, grapefruit juice, chocolate, or Seville oranges 24 hours prior to admission and throughout the study * reported use of tobacco, smoking cessation products, or products containing nicotine within 3 months prior to Screening * has an acute illness (except as described in Section 3.3.1 Inclusion Criterion b) within 14 days prior to dosing; unless approved by the Sponsor; * has any laboratory value outside the laboratory reference range considered clinically significant by the Investigator * has a history or diagnosis of Hepatitis B, Hepatitis C, human immunodeficiency virus (HIV), or thyroid disease * has a history of alcohol or illicit drug use or a positive urine drug of abuse screen * are pregnant or lactating (post-menarchal female subjects should be made aware that pregnancy testing will occur during the study, and that if they are sexually active they must take appropriate steps to ensure they do not become pregnant during the study) * has made a blood donation or plasma donation within 4 weeks prior to dosing; * has participated in another investigational drug study protocol within 30 days prior to dosing (Day -1) * has a history or presence, upon clinical evaluation, of any illness or condition that might impact safety of the subject with test product administration or evaluability of drug effect, based on the Investigator's discretion * is unable to avoid driving, operating machinery, or other tasks that require alertness during the study. * is unable or unwilling to avoid contact sports, strenuous exercises (e.g. weight lifting), exercises for which they are not trained or conditioned or intramuscular injection for at least 1 week before baseline visit when creatine phosphokinase (CPK) will be evaluated