The researchers hypothesize that the impact of increasing systemic exposure to atenolol leads to increased risk for adverse metabolic effects from atenolol therapy in hypertension. This will be accomplished through a 24-hour pharmacokinetic (PK) study and oral glucose tolerance test in hypertensive patients taking chronic atenolol 100 mg daily.

The current study is a sub-study of Pharmacogenomic Evaluation of Antihypertensive Responses (PEAR - NCT00246519). The primary objective of this pharmacokinetic (PK) study is to investigate the correlation of atenolol Cp with hypertriglyceridemia and insulin sensitivity in mild to moderate hypertensive patients after 6-8 weeks of atenolol treatment.

Participants will undergo the PK study when they have been on atenolol 100 mg once daily for at least 4 weeks and on atenolol therapy (50 mg or 100 mg) for ≥ 7 weeks. They will undergo a two hour Oral Glucose Tolerance Test (OGTT), 1 hour after atenolol dosing. Blood will be drawn at 12 time points for 24 hours. Atenolol Cp will be measured in all 12 blood samples and will be correlated with the glucose/insulin measured during the OGTT.

Inclusion Criteria:

• Subjects from PEAR who are on atenolol 100 mg once daily will be invited to participate
• Other inclusion criteria from PEAR

Exclusion Criteria:

• Patients with BMI >35 kg/m2 will be excluded
• Other exclusion criteria from PEAR