See the DrugPatentWatch profile for Phenytoin
What is Phenytoin?
Phenytoin is an anti-epileptic drug, also known as a anticonvulsant. It is primarily used to treat and prevent certain types of seizures [1].
When did Phenytoin go generic?
Phenytoin has been available as a generic medication for many years. The original brand-name formulation, Dilantin, first received FDA approval in 1953 [2].
Who makes generic Phenytoin?
Multiple pharmaceutical manufacturers produce generic versions of phenytoin. These are widely available through various pharmacies [3].
How does generic Phenytoin differ from brand-name Dilantin?
Generic medications are required to be bioequivalent to their brand-name counterparts. This means they contain the same active ingredient, in the same dosage, and are absorbed by the body in the same way [4]. While the active ingredient is the same, generic phenytoin may contain different inactive ingredients (fillers, binders, dyes) than brand-name Dilantin [5].
What are the risks of switching between phenytoin brands?
Although bioequivalent, minor differences in inactive ingredients between different phenytoin formulations can sometimes lead to variations in absorption for a small number of patients. This is particularly relevant for drugs with a narrow therapeutic index like phenytoin, where small changes in blood levels can be significant. Patients experiencing changes in seizure control or side effects after switching brands should consult their healthcare provider [6].
What is the patent status of Phenytoin?
As an older drug, the primary patents for phenytoin have long expired. This has allowed for the widespread availability of generic versions [7]. The initial patent for Dilantin was filed in the late 1930s and has long since lapsed.
What are the side effects of Phenytoin?
Common side effects associated with phenytoin can include dizziness, drowsiness, unsteadiness, nausea, vomiting, and constipation [8]. More serious side effects, though less common, can include skin rashes, changes in gum tissue, and effects on blood counts [9].
How is Phenytoin monitored?
Due to potential variability in absorption and the drug's narrow therapeutic index, phenytoin levels are often monitored through blood tests. This helps healthcare providers ensure the medication is within the effective range and minimize the risk of toxicity or sub-therapeutic effects [10].
What clinical data supports Phenytoin use?
Phenytoin has a long history of clinical use and has been studied extensively in treating generalized tonic-clonic seizures and complex partial seizures [1]. Its efficacy in controlling these seizure types is well-established [11].
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Sources
1. https://www.drugpatentwatch.com/drug/phenytoin
2. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?fuseaction=certain.list
3. https://www.goodrx.com/phenytoin
4. https://www.fda.gov/drugs/generic-drugs/what-generic-drugs
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3042746/
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6649509/
7. https://www.drugpatentwatch.com/patents/phenytoin
8. https://www.mayoclinic.org/drugs-supplements/phenytoin-oral-route-parenteral-route/side-effects/drg-20073534
9. https://www.nhs.uk/medicines/phenytoin/
10. https://www.ncbi.nlm.nih.gov/books/NBK557770/
11. https://www.neurology.org/doi/full/10.1212/01.wnl.0000159721.84377.61