As stated in the dosage and administration section of the Provigil branded modafinil tablets.
It is recommended to consume 200mg of modafinil once a day.
Thats one tablet per day, usually taken in the morning, unless being used for Shift Work Disorder, in which case modafinil should be consumed one hour prior tothe start of their work.
The below abstract describes a study conducted to better understand how modafinil is tolerated in higher doses. 200mg, 400mg and 600mg dosages (per day) were well tolerated with low incidence of adverse reacion.
However, those given 800mg showed dangerously elevated blood pressure and pulse rate.
This study concluded by suggesting no more than 600mg of modafinil per day should be ingested.
A double-blind, placebo-controlled, ascending-dose evaluation of the pharmacokinetics
and tolerability of modafinil tablets in healthy male volunteers
Wong YN, Simcoe D, Hartman LN, Laughton WB,
King SP, McCormick GC, Grebow PE
Drug Safety and Disposition,
West Chester, Pennsylvania, USA.
J Clin Pharmacol 1999 Jan; 39(1):30-40
A randomized, double-blind, placebo-controlled, ascending-dose study was conducted to evaluate the pharmacokinetic and safety profiles of increasing modafinil doses (200 mg, 400 mg, 600 mg, 800 mg) administered orally over a 7-day period in normal healthy male volunteers. Eight subjects (six modafinil; two placebo) were randomized to each of the four dose groups. Modafinil or a placebo was administered once daily for 7 days. Serial blood samples were obtained following administration of the day 1 and day 7 doses for characterization of pharmacokinetics, and trough samples were obtained prior to dosing on days 2 through 6 to assess the time to reach the steady state. Pharmacokinetic parameters were calculated using noncompartmental methods. Modafinil steady state was reached after three daily doses. Modafinil pharmacokinetics were dose and time independent over the range of 200 mg to 800 mg. Steady-state pharmacokinetics of modafinil were characterized by a rapid oral absorption rate, a low plasma clearance of approximately 50 mL/min, a volume of distribution of approximately 0.8 L/kg, and a long half-life of approximately 15 hr. Modafinil was primarily eliminated by metabolism. Modafinil acid was the major urinary metabolite. Stereospecific pharmacokinetics of modafinil were demonstrated. The d-modafinil enantiomer was eliminated at a threefold faster rate than 1-modafinil. Modalert 200 mg, 400 mg, and 600 mg doses were generally well tolerated. The modafinil 800 mg dose panel was discontinued after 3 days of treatment due to the observation of increased blood pressure and pulse rate. The safety data from this study suggest that the maximum tolerable single daily oral modafinil dose, without titration, may be 600 mg.