Question: How is the proper dosage of maintenance medication determined?
Answer: Your endocrinologist begins with a “standard” dosage of steroid, which lies within a very narrow range. For an average adult, the usual daily dosage for glucocorticoid replacement would be .5 to .75 mg of dexamethasone taken as a single dose, 5 to 7.5 mg of prednisone taken as a single dose, 20 to 30 mg of hydrocortisone taken as multiple doses, and 30 to 45 mg of cortisone acetate taken as multiple doses. The “standard” replacement dosage of mineralcorticoid would be 0.1 to 0.2 mg of fludrocortisone taken as a single dose. Fludrocortisone may not be needed by individuals with remaining adrenal glands, but is almost always required when both adrenal glands are removed. The above “standard” dosages would be lowered appropriately for children or very small adults and might be increased for very large adults. The fludrocortisone dosage might be lowered in cases of essential hypertension or heart failure and may be increased during hot summer months or if your activities caused you to lose increased amounts of salt in sweat.
In addition to body weight, other factors influence the correct dosage for an individual patient. For example, different individuals tend to metabolize, that is, to inactivate, glucocorticoids at different rates. Thus, the same dosage of steroid my be excessive for someone who metabolizes it much more slowly than average and insufficient for someone who metabolizes it much more rapidly than average. Ideally, the endocrinologist would have some sort of a test to determine a “normal” level of steroid in plasma, or a reliable index of a “normal” level of glucocorticoid activity. While plasma cortisol can be measured, the results of such a test indicate only the level of cortisone present at that particular point in time and vary according to when the last dose was taken.
Consequently, your endocrinologist must rely upon signs and symptoms of glucocorticoid excess or deficiency to adjust your dosage. If, for example, you gain weight, develop insomnia, or start getting a ruddy complexion, or have any other symptoms that are consistent with early Cushing’s syndrome, your endocrinologist will lower the dosage. Early Cushing’s symptoms that are not caused by too high of a replacement dosage include excess hair growth, and in the case of prednisone and dexamethasone, high blood pressure. In addition, if you are going to be taking glucocorticoids for a long period of time, your endocrinologist will obtain a bone density test at the beginning of treatment and at intervals of about every year, because excessive glucocorticoid replacement can cause osteoporosis.
If you develop symptoms of deficiency, which include muscle and joint aches and pains, generalized malaise, weakness, lack of energy, mild nausea, headaches, and easy fatigue, your endocrinologist may give you a trial for a week or two of increased glucocorticoid. These symptoms are not specific for glucocorticoid deficiency, but if they disappear, it is likely that they were caused by inadequate replacemnt. If they do not resolve at an increased dosage, they are problbly due to other causes, and your endocrinologist will lower the dosage back to where it was before and look for other possible causes so they can be treated. The aim is always to take the lowest dosage that is necessary to avoid symptoms of glucocorticoid deficiency.
For mineralocorticoids, the problem is much simpler. Your endocrinologist will measure your blood pressure supine and standing. If it’s too high, you may be taking too much fludocortisone. If your pressure falls when you stand, you may be taking too little. Your endocrinologist will also look for signs of fluid retention, such as ankle swelling, and measure serum sodium and potassium. If your dose is inadequate, the sodium tends be low, and the potassium high. The opposite is true if the dosage is too low. Plasma renin (an enzyme released from the kidney in response to low blood pressure) activity can also be measured. If the replacement dose is too high, renin levels will be low, and if the dosage is too low, renin levels will be elevated.
By Dr. James Findling MD (March, 1997)