Please note I do not condone the use of drugs to solve your problems ... unless the problem is say, an abscessed tooth or kidney stone in which case I can say Oxy Codone saw me through a few rough patches till I could get either extracted.
There are six drug types in use in your Traveller Universe. We'll start with Medical Slow Drug. One dose and sixty days pass for you ponder while your pals are pondering what to have for breakfast. This drug has a tech level of 7 which is absolute blather at first read. We're TL 7 and we have nothing like that. However, drugs are often refined from plants and animals in nature so this might be manufactured from a naturally occurring plant say and the refining techniques are only TL 7. Non-medical slow drug is a little more difficult to manufacture perhaps due to its shorter duration and measuring such effects so precisely.
These drugs might be a cash crop for relatively low tech worlds especially if they require a large number of life forms for harvesting. If the natural form of the drugs is available from animals then you might have to face such animals at some point and be very surprised when they get multiple actions to every one of yours.
Some worlds do prohibit the use of Slow and Medical Slow. It may seem odd in the case of Medical Slow but some people prefer that only licensed physicians would deal with a drug that can heal you at the cost of aging you a couple months.
Apparently anagathics are restricted on some worlds. This might mean it is restricted to certain social classes or occupations (no anagahics for elected officials during their term is one way to prove their dedication.)
Restricting Combat Drug seems reasonable. People use it for combat for one thing. Fr another like the other superhuman 'roids it will cause damage and possibly make you lose consciousness at the wrong time. This probably reduces its use among say, rescue workers. Passing out in a firefight is fatal enough but passing out in the middle of a fire tests the mettle of the most hardened firefighter or EMT.
Some alternate forms of Combat Drug may exist increasing either Strength or Endurance by four or Dexterity by two
I'd like you to consider extending the types of drugs. Perhaps in addition to Combat we could have Seeker: raise your Intelligence and Education by two for an hour. Reduce both by 1d6 when it wears off until the user gets eight hours sleep. Similarly Thinxfast(TM)? works to speed up the user's thought processes allowing them to get an hour of contemplation in a few minutes. Good for working out complex problems. The only problem is your body is paralyzed while the drug is working. I'd recommend at least 2d6 in wounds for this to Dex, Int or Edu and limit the use to once per week.
What about Mindblok(TM)? Take a dose and you have a psi shield equal to your Intelligence in strength for 1d6 hours. This is not an option for natural telepaths who will fall unconscious for 2d6 hours and take 2d6+6 wounds.
Nootralizer(TM) is the opposite of the psi drugs and used as a more humane way of holding psionic humans captive. One dose reduces psionic strength by eight for 20 - Endurance hours. It does not inflict any damage on the subject and is taken by injection allowing it to be used in special tranq ammunition for snub pistols.