Mood drug

Mood drugs were chemical-releasing cellophane patches used by the people of New Earth around 5,000,000,000.

Typically harmless, the patches that were available had many different effects: some, such as Happy, Anger, and Mellow, altered the user's emotions, and others such as Sleep, Honesty, Read and Forget, altered the user's body and mind in other ways. It was possible that some, if not all, of the mood patches came in different degrees of strengths or duration up to at least forty-three. (TV: Gridlock)

Mood patches did not work on the Twelfth Doctor. (TV: Dark Water)

History
The people of New Earth used mood drugs from sometime before 5,000,000,023 until 5,000,000,053, typically in the New New York Undercity, including Pharmacytown. One mood drug, however, Bliss, was only found in the upper levels of New New York, where it became extremely addictive. Soon, an airborne virus mutated in it, which spread and killed the entire population of the upper levels within seven minutes, except the Face of Boe in his life-support tank and Novice Hame, whom Boe surrounded with his smoke. The inhabitants of the Undercity and those in the Motorway survived, and with no one to feed on, the virus eventually starved to death and became extinct.

After the Tenth Doctor and Martha Jones travelled to the Undercity, they came across the markets in Pharmacytown, where they learned of the drug from Pharmacist 1, 2, and 3. The Doctor attempted to stop a pale woman from using the Forget drug to forget her parents who travelled to the Motorway, but he was unsuccessful. Shortly after, Milo and Cheen used Sleep to incapacitate Martha so they could kidnap her and use her to gain access to the Fast Lane, as three people were needed. Later, after Novice Hame took the Doctor to the Senate, she explained the destruction wrought by the Bliss drug. The Doctor was then able to free the people in the Motorway as there was now no longer any threat of a virus. (TV: Gridlock)

Undated events
The Twelfth Doctor kept mood patches aboard the TARDIS. Clara stole what she thought was a Sleep patch from his supply and attempted to incapacitate the Doctor and blackmail him into saving her boyfriend, Danny Pink. The Doctor revealed that the mood patches did not work on him and that he had instead used the patch to put Clara in a dream-state. (TV: Dark Water)

A Crespallion was selling Mellow in an alien marketplace visited by a group of humans from the 21st century. (PROSE: And now for a story...)

Behind the scenes
In the real world, transdermal patches have been used for the administration of medicine since the 1970s, first being used for motion sickness, before expanding to birth control, nicotine patches, and even caffeine patches, all of which act on mood, just like the mood patches in TV: Gridlock.