the Fatwa Department Research Committee - chaired by Sheikh `Abd al-Wahhâb al-Turayrî
It is unlawful for doctors to sell to their patients the medical samples given to them by pharmaceutical companies.
From the standpoint of Islamic Law, these samples are not a gift (hadiyyah) but rather a trust in deposit (wadî`ah). The company entrusts the doctor with the medications to be used specifically as samples – meaning that they are to be given to patients who need to try those medications or to those professionals who wish to examine or study the medications.
Anybody who falls into one of those two categories – including the doctor – may utilize the medical samples for one of these legitimate purposes.
These medications may not be sold. Indeed, that is often a specific written condition on the package and it is something contractually specified for anyone who wishes to accept the trust in deposit.
Anyone who sells the medical samples is violating the trust.
Allah says: “O ye who believe! Betray not Allah and His messenger, nor knowingly betray your trusts.” [Sûrah al-Anfâl: 27]
And Allah knows best.
Source: Islam Today