Interaction

Most medications can be safely used with other medicines but particular
combinations of medicines need to be monitored for interactions, often by
the pharmacist.

Sometimes two or medications are used together to create an extra effect -
e.g. two different pain killers to provide more complete pain control. These
interactions are usually intentional but need to be monitored by the doctor
because patients can end up with more effect than is actually required.
Sometimes two or medications work against each other. These interactions are
usually well-known and avoided unless both medicines are essential. Careful
monitoring is used to prevent problems from the results of the interaction.
Other interactions may cause one medicine to have less or more effect than
expected and these are usually managed by a dosage adjustment.