Drug Side Effects
The organization of the ANS permits an
understanding of effects that drugs can have on organs other
than those that are the intended targets of drug action. For example, drugs
that are designed to reduce heart rate by activating mAChRs on the heart
activate mAChRs throughout the ANS unless subtypes of mAChR were identified on
the heart and the drug selectively activates that subtype. The therapeutic and
adverse effects of a drug are sometimes a function of intended use. The same
drug (eg, an mAChR antagonist) in one clinical setting may be
given to treat diarrhea and cause sensitivity to light (mydriasis)
as an adverse effect; in another clinical setting, the drug may be used
therapeutically for an eye examination, but it could cause constipation as an
adverse effect. The drug-induced effects are the same in both cases. Also,
drugs that have different therapeutic targets can share a
similar side effect.
