Metabolism of propanoate begins with its conversion to propionyl coenzyme A (propionyl-CoA), the usual first step in the metabolism of carboxylic acids. Since propanoic acid has three carbons, propionyl-CoA can directly enter neither beta oxidation nor the citric acid cycles. In most vertebrates, propionyl-CoA is carboxylated to D-methylmalonyl-CoA, which is isomerised to L-methylmalonyl-CoA. A vitamin B 12 -dependent enzyme catalyzes rearrangement of L-methylmalonyl-CoA to succinyl-CoA, which is an intermediate of the citric acid cycle and can be readily incorporated there.
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Initial dose based on previous asthma drug therapy and disease severity; 100 mcg via oral inhalation once daily is the usual recommended starting dose for patients not on an inhaled corticosteroid. After 2 weeks of therapy, if asthma symptoms are uncontrolled, increase dose to 200 mcg via oral inhalation once daily. Max: 200 mcg once daily. Administer at the same time each day. The maximum beneficial effect may not be achieved for up to 2 weeks or longer after starting treatment. Titrate to the lowest effective dose once asthma stability is achieved.