There are many drugs in the universe, and the Colonials use them like other races. All medical drugs found in GURPS Space 3rd Edition page 94 (save Torpine and Anti-Agathics which do not exist) are available to players, although Adders are very rarely used and generally illegal. In addition, there are a number of recreational drugs available as well as a few special drugs that are in use, if not legally.
The typical recreational drug is not actually legal to use, but most law enforcement agencies turn a blind eye and unless you do something completely stupid whilst under the influence, you will not be stopped for taking it or being under the influence. Comes in either a pill, liquid or smoke-able form, the effects of a recreational drug generally make the user feel high and on a euphoric trip. While you are able to function while taking them, your coordination does go a bit and you end up not making a lot of sense to others if you talk to them. Trips last a couple of centars with no real side effects. The drug tends to cost around 50 cubits a shot and can be obtained with a simple streetwise skill roll. These drugs are mildly addictive, and if more than two doses are taken in 24 centars, an addiction roll should be made.
Brain Crystals are addictive drugs that scramble the brain, make the user hallucinate, think they're in a dream world and generally not live in the now. When on the trip, the user will not recognise their surroundings nor the people they are with. In fact, they may not even know someone is around at all, they will be so out of it. It will be impossible to interact with someone taking Brain Crystal. They will not eat or rest during the time. When they come down, a user gets the shakes as the drug is expunged from their system, and they get very confused as their brain tries to make some sense of what has just happened. Regular users will start to get paranoid, permanently shake and hallucinate even while not taking the drug. Sometimes though, the drug may revive old memories, even ones lost to Short Spans, although this is not a safe way to get those memories back. A trip lasts around 2d6 centars. Addiction will occur if more than one dose is taken in a 24 centar period. The drug is illegal, although has sometimes been prescribed and issued (under controlled conditions) by hospitals treating memory loss conditions. It costs 400 cubits per dose.
Comas are drugs which, when taken, force the victim to enter a period of deep sleep. This is a forced sleep and not able to help the character heal or rest at all, and thus you will not get this drug prescribed for medical uses. In fact, this drug is illegal and was designed to be slipped to someone who would then be incapacitated. The drug is available in capsule form (which is easily dissolved in liquid), and when ingested, the target will fall into a deep sleep in about HT centons time. Once asleep, it will take a lot to rouse the character - loud noise, slapping, cold water will not generally work, but a dose of the Revive drug will. In fact, this inability to revive the victim is generally how the drug got its name of Coma. If undisturbed, the character will sleep for about 10 centars, and will awaken normally and with no side effects save for having a headache and feeling tired. The drug is not addictive and can be found on the black market or by someone with contacts in the intelligence circle. Coma's generally cost around 75 cubits per dose.
Paralysis capsules can be taken orally, injected or as vapour. When ingested somehow, the effects are instant. The target will be immobilised and paralysed for a few centons, although they will be aware of what is going on around them, just not able to participate. The drug is not addictive, but illegal. It does carry some risk in that a small percentage of people find that their heart also gets paralysed which leads to death. (Make an HT+2 roll, failure indicates a heart attack). There is no antidote to a paralysis capsule, but as stated, with the exception of a few people, the drug does not actually cause any harmful side effects. On the black market, the drug costs around 500 cubits per dose.
Short Spans were developed to make someone forgot the last few moments of their life. The drug attacks the brain cells and destroys the victims' short term memory. It is very effective in its task, and there are not many means of being able to get those memories back. Hypnotism and other drugs will not work, but psycho-electron recall will, but you have to be a brave person to want to submit to that. Unlike some other drugs, a short span effect will not wear off over time, so memories will not start coming back in dreams or visions at some point in the future. As far as the victim is aware, the last few moments just do not exist. Short Spans are illegal, but available on the black market. They are very addictive if used more than once a day on someone. A short span will destroy the last (30 - HT) centons of someone's life, starting from the moment the drug is taken. Multiple doses therefore, will not extend this period of time. The drug costs 250 cubits and is available in capsule or liquid form.