Patients can eat and drink normally and take all their usual medications prior to the test. Estrogen containing medications, including the contraceptive pill and hormone replacement therapy, should be stopped for six weeks prior to measuring serum cortisol. This is because estrogen induces cortisol binding globulin and leads to elevations in measured serum cortisol. Any steroid containing medications should also be documented, and avoided if possible, as they may interfere with the hypothalamo-pituitary-adrenal axis, or cross react with the cortisol assay.
The recommended dose is one or two drops (solution or ointment) or one drop (suspension) into the conjunctival sac every four to six hours. The dosing interval may be reduced to every two hours during the initial 24 to 48 hours. The hands should be washed before each use of Tobradex or any eye medication. The head is tilted back, and the lower eye lid is pulled down with the index finger to form a pouch. The tip of the dropper should not touch the eye or eyelid . The bottle of Tobradex should be squeezed slightly to allow the prescribed number of drops (generally one or two drops) into the pouch. If the ointment is being used, a small strip (about 1cm or 1/2 inch) of ointment should be squeezed into the pouch. The eye should then be closed gently for one to two minutes without blinking.