 This is a 52 week Phase III double-blind, randomized, placebo-controlled study of adjunctive clenbuterol in LOPD Table 2, Section 6. All subjects will be evaluated at Week 0 and Week 6 to establish a baseline for motor function testing. At Week 6, subjects will be randomized 3:2 to clenbuterol or placebo, and evaluated for safety and efficacy during the Week 12 and 18 visits. The Investigational Drug Service will maintain double-blinding by providing either the study drug or placebo over-encapsulated tablets directly to subjects. The drug or placebo will be initiated at the Week 6 visit in a staged manner first once daily and later BID, and the dose will be increased at the Week 12 visit in a similarly staged manner to minimize AEs and related attrition. All subjects will return for a final visit after a total of 52 weeks in the study. 