A woman has been prescribed a daily iron supplement by her health care provider.She recently became constipated,most likely related to the iron supplement.Which of the following best describes this response?

A) Therapeutic effect
B) Adverse reaction
C) Side effect
D) Toxicity

A side effect is a predictable and often unavoidable secondary effect produced at a usual therapeutic dose.Each medication has a therapeutic effect,the intended or desired physiological response of a medication.Undesired,unintended,and often unpredictable responses to medication are referred to as adverse effects.Toxic effects are capable of causing injury or death.They often develop after prolonged intake of a medication or when a medication accumulates in the blood because of impaired metabolism or excretion.