Schizophrenia Q 11
Drug therapy with thioridazine (Mellaril) shouldn’t exceed a daily dose of 800 mg to prevent which adverse reaction?
A. Hypertension
B. Respiratory arrest
C. Tourette syndrome
D. Retinal pigmentation
Correct Answer: D. Retinal pigmentation
Retinal pigmentation may occur if the thioridazine dosage exceeds 800 mg per day. The development of pigmentary retinopathy is a unique adverse manifestation associated with thioridazine, and not with other antipsychotics. Patients may have nonspecific symptoms while taking thioridazine, such as dry mouth, dry eyes, sedation, weight gain, dizziness, erectile dysfunction, pruritus, photosensitivity, and constipation. Other rare and more unique side effects of thioridazine include irreversible retinal pigmentation, poikilothermia, and agranulocytosis.
Option A: Thioridazine is associated with prolonged QTc intervals, which may have serious or even fatal consequences, such as Torsades de pointes. The recommendation is that patients with known prolonged QTc or arrhythmias avoid thioridazine. Before starting this medication, it would be wise to order an ECG and monitor for QTc prolongation or other ECG changes during treatment.
Option B: Respiratory arrest is not an adverse effect of thioridazine. NMS is another serious side effect of all antipsychotics and occurs more frequently with typical antipsychotics. This adverse effect may occur suddenly. The provider should monitor for unstable vital signs, such as tachycardia, fever, muscle rigidity, elevated white blood cell count, and creatinine phosphokinase.
Option C: The other options don’t occur as a result of exceeding this dose. Similar to other typical antipsychotics, thioridazine is associated with a risk of developing EPS. Because it is a low potency antipsychotic, however, the development of EPS occurs less frequently than with high potency antipsychotics. Extrapyramidal side effects include symptoms of dystonia, parkinsonism, and tardive dyskinesia. Dystonic reactions are muscle spasms that may occur early on and involve the eyes, tongue, or neck.