On a second thought, I'll use a modified (simpified) version of the rules presented by Andy Slack in
Expanding Universe. While I'll be using his core concept (initial, secondary and tretiary effects, each with its own saving throw), I'll change many of the rule specifics. For example, I'll ignore his dosage and body-mass rules for the sake of a simpler system, and assume that the characters have been exposed to an "average dose". The main exception for this would be radiation (which would become a new "poison" for every given amount of rads you accumulate - a few rads will be a very mild poison, but when you accumulate quite alot of rads, you'll have very nasty radiation sickness and/or cancer).
Every poison has three effects: Initial, Secondary and Tretiary. When the character is exposed to the poison, the Referee rolls three saving throws in secret. Each saving throw is made by a roll of END or less on 3D, with a DM based on the poison's strength (the stronger the poison, the higher the DM). A natural roll of 18 is always a failure; a natural roll of 3 is always a success. If the character succeeds all three rolls, he's uneffected by the poison. If the character fails one roll, he suffers only the Initial effect. If he fails two rolls, he suffers both the Initial and the Secundary Effects. If he fails all three rolls, he suffers the all of the effects. Death effects are always Tretiary.
Each effect has a Time parameter - the time it takes for it to take effect. For example, if a poison has a Time of 1 combat turn for its Initial effect, of 1 hour for its Secondary effect and of 10 minutes for its Tretiary effect, a character who fails all three saving throws for that poison, he'll suffer the Initial effect one combat term after the exposure, the Secundary effect an hour later (an hour and one combat term after the exposure) and the Tretiary effect 10 minutes after that (one hour, 10 minutes and a combat turn after the initial exposure).
Treating a poison require an antidote or medical attention. Treatment must start to be administered before the Tretiary effect takes place in order to be effective.
An efficient antidote negates the poison, though the character will usually take time to recover from all effects - usualy 4d6 hours. If the poison has caused attribute damage, the character recovers only when all damage is healed.
Alternatively, if an antidote is not readily available, it may be synthesized. At TLs 0-4 this could only be done in very rare cases (referee discretion) and requires a
Medic/EDU/-4 task and time to collect herbs, minerals and so on. At TLs 5-8, antidotes could be synthesized at ospitals by a doctor (Medic-3 or better) for most poisons within 1d6 hours, with a successful
Medic/EDU/-2 task throw (DM +2 if the doctor also has a skill of Chemistry-2 or better or if she's being helped by someone with such a skill). At TLs 9-12, antiotes may be synthesized by an automatic laboratory in clinics as well (the autolab has Medic-3, Chemistry-2 and EDU-7 for the sake of this roll); at TL13+, a medkit is capable of synthesizing most antidotes in a similar manner. However, the poison must be identified in order for an antidote to be synthesized for it (see below).
On TL16+, a nanotec-based Pantidote drug is available which is capable of negating most poisons; however, even at that TL it is quite expensive.
A medic (Medic-1 or better) with a Medkit may delay the onset of any further symptoms by 1d6 hours with a successful
Medic/INT task with the difficulty DM equal to the saving-throw DM of that poison. At the Referee's discretion, the Medic might also alleviate certain effects.
All kinds of clinical medical attention for poisons requires the nurse or doctor to identify the poison; this is a UGM task of
Medic/EDU with the difficulty DM determined by the poison. Failure to identify the poison precludes medical attention, though retries are possible until the Tretiary effect takes place. Each attempt takes 2d6x10 minutes (or how long should that be?) unless the referee states otherwise (for example, in the case of a snakebite, if the snake itself is brought to the doctor and its species is identified, the poison is identified as well).
A nurse or medtech (Medic-2 skill or better) in a clinic could help combat the poison's effects rather than remove the poison itself; re-roll the three saving throws, but this time add the medtech's Medic skill to the character's Endurance. If the character succeeds all three rolls, he starts to recover as above. If the character fails one roll, he suffers only the Initial effect while allevating the Secundary effect. If he fails two rolls, he suffers both the Initial and the Secundary Effects but avoids the Tretiary effect. If he fails all three rolls, he still suffers the all of the effects.
A doctor (Medic-3 or better) in a hospital may successfully combat all of the effects of the poison with a successful
Medic/INT task with the difficulty DM equal to HALF the saving-throw DM of that poison (round down). This means using intensive care to deal with severe respiratory effects, using pain relievers to deal with pain, and even replacing damaged organs if nescery.
