Final answer:
Relief from headaches indicates the intended effects of ergotamine tartrate, a medication used to treat acute migraine headaches by constricting blood vessels and reducing inflammation.
Step-by-step explanation:
The nurse can determine that ergotamine tartrate is having its intended effect if the client experiences relief from headaches. Ergotamine tartrate is a medication primarily prescribed for the treatment of acute migraine headaches. It works by constricting blood vessels around the brain and reducing inflammation associated with migraine headaches.
While ergotamine may have several side effects such as nausea, vomiting, abdominal pain, and others, it is not typically used to treat symptoms like cough, diarrhea, or backache. Therefore, the most appropriate choice from the given options would be relief from headaches number 4, indicating successful therapy with this medication.