Prescribing-label excerpts
Dichlorphenamide
Reference for: Dichlorphenamide. Source presentation: tablet. Source route: oral.
Mechanism of action
Dichlorphenamide is a carbonic anhydrase inhibitor. However, the precise mechanism by which dichlorphenamide exerts its therapeutic effects in patients with primary periodic paralysis is unknown.
Pharmacokinetics
After single-dose administration in healthy subjects in fasted state, dichlorphenamide C max and AUC increased in a dose-proportional manner within the range of 25 mg to 400 mg (2 times the maximum recommended dose). The steady-state is expected to be achieved within 10 days of twice-daily dosing.
Absorption — The median time to reach maximum concentration (T max) of dichlorphenamide was about 1.5 to 3 hours postdose after both single and multiple dose administrations.
Distribution — The plasma protein binding of dichlorphenamide is approximately 88%.
Elimination — Following a single-dose administration, mean terminal half-life was in the range of 32 to 66 hours.
Metabolism — Dichlorphenamide is not a substrate for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4 isoforms when tested in vitro.
Drug-Metabolizing Enzyme Inhibition — Dichlorphenamide is not an inhibitor for CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4 enzymes when tested in vitro.
Drug-Metabolizing Enzyme Induction — Dichlorphenamide is not an inducer for CYP1A2, 2B6, or 3A4 enzymes when tested in vitro.
In vitro Assessment of Transporter-Drug Interactions — Dichlorphenamide is neither a substrate nor inhibitor for p-gp, BCRP, OATP1B1, OATP1B3, OAT2, OAT4, OCT1, OCT2, MATE1, or MATE2-K when tested in vitro.
Dichlorphenamide is not an inhibitor of OAT3, but is an inhibitor of OAT1 based on in vitro studies [see Drug Interactions ( 7.4)].
Dichlorphenamide is a substrate for transporters OAT1 and OAT3 based on in vitro studies [see Drug Interactions ( 7.2)]
In Vivo Drug Interactions — The use of dichlorphenamide in combination with high-dose aspirin is contraindicated as it may lead to salicylate toxicity. The mechanism(s) of this interaction is not known.
Geriatrics — The pharmacokinetics of dichlorphenamide in the elderly has not been determined.
Selected passages from the cited U.S. prescribing label. The studies concern the source product and populations named in each passage; they do not establish Walter-product bioequivalence, an approved indication, or the kinetics of another fixed combination. Tables and the full prescribing information remain available in the source.
Source: DailyMed: Dichlorphenamide — tablet
Reference accessed . Label revision: 2026-03-05.
