In Jain Dharma, preserving health is important, and medicine may be taken even after sunset if it is necessary.

However, the water used should be as carefully handled as possible, because Jain practice emphasizes ahimsa and avoiding harm to living beings in water after sunset. So:

• If the medicine is necessary, taking it is generally acceptable.
• If possible, use the minimum water needed.
• For strict vrat, upvas, or higher vows, the observance may be more careful, and the guidance of a Sadhu/Sadhvi or knowledgeable Jain guru is followed.

So the simple answer is: Yes, if it is necessary for health, medicine can be taken after sunset even if water is needed, but with care and restraint.