The purpose of this study is to compare the safety and effectiveness of 1300 mg acetaminophen extended release given three times daily for nine days to that of 400 mg ibuprofen given three times daily for nine days for the signs and symptoms of (Grade I and Grade II) lateral ankle sprains.

The objective of this randomized, double-blind, parallel-group study is to compare the safety and effectiveness of 1300 mg acetaminophen extended release given three times daily for nine days to that of 400 mg ibuprofen given three times daily for nine days for the signs and symptoms of Grade I and Grade II lateral ankle sprains. The primary efficacy endpoint is the change from baseline (Day 1) to Day 4 in the subjects' pain upon walking. Safety assessments consist of the monitoring of adverse events and assessments of the ankle injury during the course of the study. Two hypotheses are examined using a step down approach. The first hypothesis is that acetaminophen extended release is not inferior to ibuprofen in relieving the pain associated with (Grade I or Grade II) lateral ankle sprains. If acetaminophen extended release is not inferior to ibuprofen in relieving the pain associated with Grade I or Grade II lateral ankle sprains, the second hypothesis is that acetaminophen extended release is superior to ibuprofen in relieving the pain associated with Grade I or Grade II lateral ankle sprains. Two acetaminophen 650 mg extended release caplets, taken by mouth, three times a day for nine days or two ibuprofen 200 mg caplets, taken by mouth, three times a day for nine days

Inclusion Criteria:

• Have had an ankle sprain within 24 hours of study entry
• have ankle pain when walking
• have not recently used non-steroidal, anti-inflammatory drugs (NSAIDs), other pain relieving medications (including acetaminophen) or medicines that could interfere with the assessment of effectiveness
• if female, must not be pregnant or breastfeeding

Exclusion Criteria:

• Ankle sprain was the second ankle sprain within six months
• Both ankles were sprained
• Ankle sprain occurred on the same side of the body as a knee injury
• Ankle injury requires bed rest, hospitalization, surgical intervention, or use of a non-removable rigid cylindrical cast
• Subject reports severe or very severe pain at rest on a five-point scale of none, mild, moderate, severe or very severe