Single Ascending Dose
Single ascending dose studies are those in which small groups of subjects are given a single dose of the drug while they are observed and tested for a period of time. Typically, a small number of participants, usually three, are entered sequentially at a particular dose. If they do not exhibit any adverse side effects, and the pharmacokinetic data is roughly in line with predicted safe values, the dose is escalated, and a new group of subjects is then given a higher dose. If unacceptable toxicity is observed in any of the three participants, an additional number of participants, usually three, are treated at the same dose.This is continued until pre-calculated pharmacokinetic safety levels are reached, or intolerable side effects start showing up (at which point the drug is said to have reached the maximum tolerated dose (MTD)).
Example: Single Ascending Dose First-in-Human Study of a Novel Ant malarial Drug (CDRI 97/78)
The starting dose was 80 mg; calculation of starting dose was based on the basis of maximum tolerated dose of 100 mg/kg obtained in rats. This was used to obtain a dose of 96 mg for a 60 kg man. The formulation which was available for a dose below this was of 80 mg and hence taking these factors into consideration a starting dose of 80 mg was chosen. The following dose levels were evaluated: 80, 160, 320, 400, 500, 600, and 700 mg. The starting dose was calculated by allometric scaling from animals. At each dose level, volunteers were assessed before proceeding to the next dose. The decision to dose only 2 volunteers was taken, after analysis of data of 600 mg, wherein no remarkable adverse events were noted.
The decision to stop the dose escalation was based on the appearance of the dose limiting toxicity (DLT) which was defined as the dose at which any of the following appeared: severe nausea, vomiting, heartburn, headache, remarkable change in vital parameters such as blood pressure, heart rate, respiratory rate or oxygen saturation of blood, changes in QT interval, or any event that in the opinion of the investigators required stopping of the trial.
Multiple Ascending Dose:
Multiple ascending dose studies (MAD) are designed to test the pharmacokinetics and pharmacodynamics of multiple doses of the experimental drug. A group of subjects receives multiple doses of the drug, starting at the lowest dose and working up to a pre-determined level. At various times during the period of administration of the drug, and particularly whenever the dose is increased, samples of blood and other bodily fluids are taken. These samples are analysed in order to determine how the drug is processed within the body and how well it is tolerated by the body.