In addition to all of the above, primidone can cause arthralgia.Granulocytopenia, agranulocytosis, and red-cell hypoplasia and aplasia, and megaloblastic anemia are rarely associated with the use of primidone. Megaloblastic anemia is actually a group of related disorders with different causes that share morphological characteristics—enlarged red blood cells with abnormally high nuclear-cytoplasmic ratios resulting from delayed maturation of nuclei combined with normal maturation of cytoplasm, into abnormal megakaryocytes and sometimes hypersegmented neutrophils; regardless of etiology, all of the megaloblastic anemias involve impaired DNA replication. The anticonvulsant users who get this also tend to eat monotonous diets devoid of fruits and vegetables.This antagonistic effect is not due to the inhibition of dihydrofolate reductase, the enzyme responsible for the reduction of dihydrofolic acid to tetrahydrofolic acid, but rather to defective folate metabolism.In addition to increasing the risk of megaloblastic anemia, primidone, like other older anticonvulsants also increases the risk of neural tube defects, and like other enzyme-inducing anticonvulsants, it increases the likelihood of cardiovascular defects, and cleft lip without cleft palate. Epileptic women are generally advised to take folic acid, but there is conflicting evidence regarding the effectiveness of vitamin supplementation in the prevention of such defects.Additionally, a coagulation defect resembling Vitamin K deficiency has been observed in newborns of mothers taking primidone.
Folic acid had been found to alleviate the symptoms of megaloblastic anemia in the 1940s, not long after it was discovered, but the typical patient only made a full recovery—cessation of CNS and PNS symptoms as well as anemia—on B12 therapy. Five years earlier, folic acid deficiency was linked to birth defects in rats. Primidone was seen by some as too valuable to withhold based on the slight possibility of this rare side effect and by others as dangerous enough to be withheld unless phenobarbital or some other barbiturate failed to work for this and other reasons (i.e., reports of permanent psychosis). Available forms
Primidone is available as a 250 mg/5mL suspension, and in the form of 50 mg, 125 mg, and 250 mg tablets. It is also available in a chewable tablet formulation in Canada.It is marketed as several different brands including Mysoline (Canada, Ireland, Japan, the United Kingdom, and the United States), Prysoline (Israel, Rekah Pharmaceutical Products, Ltd.), Apo-Primidone, Liskantin (Germany, Desitin), Resimatil (Germany, Sanofi-Synthélabo GmbH), Mylepsinum (Germany, AWD.pharma GmbH & Co., KG)., and Sertan (Hungary, 250 mg  tablets, ICN Pharmaceuticals Inc.[1])

Other animals
Primidone has veterinary uses, including the prevention of aggressive behavior and cannibalism in gilt pigs, and treatment of nervous disorders in dogs and other animals. References
Further reading
"Toxicology and Carcinogenesis Studies of Primidone in F344/N Rats and B6C3F1 Mice (Feed Studies)" (PDF). Department of Health and Human Services National Toxicology Program. September 2000. Lay summary. {{cite web}}: Cite uses deprecated parameter |lay-url= (help)

External links
"Primidone". Drug Information Portal. U.S. National Library of Medicine.