A. Pain
1. Morphine
Pain precipitates and aggravates autonomic disturbances which may cause arrhythmias, hypotension, or hyperten¬sion, thus increasing the size of infarction. Pain relief must be achieved immediately. Morphine is the drug of choice for relief and should be given slowly intravenously: 4–8 mg IV at a rate of 1 mg per minute repeated if necessary at a dose of 2–4 mg at intervals of 5–15 minutes until pain is relieved. Morphine allays anxiety, relieves pain, and causes venodilatation, therefore, reducing preload. This is of some benefit in patients with left ventricular failure.
2. Beta-Blockers
Beta-blockers must be given a more important place in the management of chest pain resulting from myocardial infarction. They can be considered as important second-line agents for the control of ischemic pain. This is important in patients with acute infarction accompanied by sinus tachycardia and systolic blood pressure greater than 110 mmHg. Dramatic pain relief and reduction of ST segment elevation can be obtained by the administration of a beta-blocking agent and the requirement for opiates is thus reduced. In some patients pain has been documented to be relieved by the administration of beta-blockers without concomitant use of opiates. Metoprolol 5 mg at a rate of 1 mg per minute is repeated if necessary at 5-minute intervals to 10 mg. A maximum dose of 50 mg followed by an oral dose of 50 mg every 12 h can be given if no contraindication exists (asthma, heart block, bradycardia of less than 50 beats per minute, and blood pressure less than 90 mmHg diastolic).

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