Doxycycline to Protect Heart Muscle After Heart Attacks

Patients will receive placebo in a loading dose of two capsules initially followed by one capsule every 12 hours for 7 days.

Patients will receive doxycycline hyclate in a loading dose of two 100 mg capsules (200 mg total) initially followed by one 100 mg capsule every 12 hours for 7 days.