Genetics of Glycogen-Storage Disease Type V Medication

Updated: Nov 10, 2015
  • Author: Edward J Cupler, MD, FAAN; Chief Editor: Maria Descartes, MD  more...
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Medication

Medication Summary

In general, no specific treatment is indicated for McArdle disease (glycogen-storage disease type V). Vitamins such as vitamin B-6 (pyridoxine) may be beneficial to correct depleted body stores and augment myophosphorylase activity. Sucrose may improve exercise tolerance. Creatine may improve ATP capacity and exercise tolerability.

Other treatments, such as d-ribose, glucagon, verapamil, and dantrolene, have not been shown to be effective. Branched-chain amino acids were shown to worsen functional activity and exercise capacity.

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Vitamins

Class Summary

These agents are necessary to promote regular growth and good health. Some studies suggest that pyridoxine may reduce the susceptibility of muscles to fatigue in patients with McArdle disease. Normally, myophosphorylase uses pyridoxal 5'-phosphate (derived from vitamin B-6) as a cofactor; therefore, supplementation may augment the remaining myophosphorylase activity. In addition, most of the total body pool of pyridoxine is normally bound to myophosphorylase; therefore, the body's store of pyridoxine may be depleted in patients with McArdle disease.

Pyridoxine (Nestrex)

Vitamin B-6 is a naturally occurring vitamin normally found in beans, grains, liver, meats, eggs, and vegetables.

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Nutritional Agent

Class Summary

Sucrose is a disaccharide that is readily split into glucose and fructose. These sugars circumvent the metabolic block in individuals with McArdle disease. Recently, sucrose (75 g 30 min PO before exercise) was shown to improve exercise tolerance to the point that no "second wind" phenomenon is observed.

Sucrose

Disaccharide from sugar cane made up of d-glucose and d-fructose.

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Nutritional Supplement

Class Summary

Creatine monohydrate supplementation may increase ATP availability and exercise capacity. A single study demonstrated an increase in exercise capacity while low-dose creatine monohydrate (60 mg/kg/d) was administered. Interestingly, a subsequent study by the same group revealed a deleterious effect at a dosage of 150 mg/kg/d. [14]

Creatine monohydrate

Increases intracellular creatine and phosphocreatine levels. Converted to creatinine. Theorized to increase short-term energy supply to muscle tissue by rephosphorylation of ADP. Unknown if increased creatine in muscle improves athletic performance in nondepleted conditions.

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Angiotensin-Converting Enzyme (ACE) Inhibitor

Class Summary

Investigators studying a small cohort of 8 adult patients reported that treatment with 2.5 mg of ramipril subjectively improved reported scores of perceived disability but had no effect on objective functional outcomes measures. The improvement in the perceived disability scores was more pronounced in the D/D genotype and was absent in the I/D genotype. Although not significant, the D/D genotype also showed a slight improvement in peak VO2. The improvement in peak VO2 and subjective disability scores suggest a benefit of ramipril treatment in patients with the D/D genotype, but additional testing of a larger patient population is needed. [15]

Ramipril (Altace)

Prevents conversion of Angiotensin I to angiotensin II, a potent vasoconstrictor, resulting in increased levels of plasma renin and a reduction in aldosterone secretion.

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