A woman visits a health center requesting oral contraceptives. Which laboratory test is most important for the nurse to assess before the patient begins oral contraceptive therapy?

Choice A reason: Vaginal cultures are not necessary for oral contraceptive therapy. They are used to diagnose infections such as bacterial vaginosis, yeast infection, or sexually transmitted diseases.

Choice B reason: Complete blood count is not essential for oral contraceptive therapy. It is used to measure the number and types of blood cells, such as red blood cells, white blood cells, and platelets.

Choice C reason: Serum potassium level is the most important laboratory test for oral contraceptive therapy. This is because some oral contraceptives can increase the risk of hyperkalemia, which is a high level of potassium in the blood. Hyperkalemia can cause serious complications such as cardiac arrhythmias, muscle weakness, and paralysis.

Choice D reason: Pregnancy test is not a laboratory test, but a urine test. It is important to rule out pregnancy before starting oral contraceptive therapy, but it is not the most important test for the nurse to assess.

Choice A reason: Tachycardia is a possible adverse effect of theophylline, as it is a methylxanthine that stimulates the central nervous system and the cardiac muscle. The nurse should instruct the client to monitor their pulse rate and report any palpitations, chest pain, or irregular heartbeat.

Choice B reason: Drowsiness is not a likely adverse effect of theophylline, as it is a stimulant that increases alertness and energy. The nurse should caution the client to avoid taking the medication close to bedtime, as it may cause insomnia.

Choice C reason: Constipation is not a common adverse effect of theophylline, as it does not affect the gastrointestinal motility or secretion. The nurse should advise the client to maintain a balanced diet, adequate fluid intake, and regular exercise to prevent constipation.

Choice D reason: Oliguria is not a typical adverse effect of theophylline, as it does not impair the renal function or cause fluid retention. The nurse should encourage the client to drink enough fluids to prevent dehydration and maintain a normal urine output.