Usually, clinical trial participants are not paid for participating because the offer of money should never be the reason for deciding to join a trial. (The exception to this is Phase I trials which involve healthy volunteers).
However, reasonable expenses – such as travel costs – incurred by clinical trial participants will be paid back to them. In some cases, participants receive small sums to compensate them for their time and may receive food or refreshments if they have to come to a clinic frequently or are kept waiting.
Participants never have to pay for any trial-related care they receive – this is always provided at no cost to them or to those who might normally fund their healthcare.