There is a wide range of oral amitriptyline hydrochloride dosage requirements, and dosage must be carefully individualized.
Patients should be monitored for possible worsening of depression, suicidality, or unusual changes in behavior, especially at the beginning of therapy or during periods of dosage adjustment.
Initial dosages should be low and generally range from 75-100 mg daily, depending on the severity of the condition being treated. Dosage may be gradually adjusted (preferably the late-afternoon and/or bedtime doses) to the level that produces maximal therapeutic effect with minimal toxicity and may range from 150-300 mg daily. Alternatively, the manufacturers recommend an initial amitriptyline hydrochloride dosage of 50-100 mg daily at bedtime. Dosage then can be increased by 25 or 50 mg as necessary to a suggested maximum of 150 mg daily. Hospitalized patients under close supervision may generally be given higher dosages than outpatients. Hospitalized patients generally may receive an initial amitriptyline dosage of 100 mg daily; dosage may be increased gradually to 200 mg daily as needed. Some patients may require dosages as high as 300 mg daily. Geriatric and adolescent patients should usually be given lower than average dosages. Manufacturers state that these patients may obtain satisfactory improvement with 10 mg of amitriptyline hydrochloride 3 times daily plus 20 mg at bedtime. Maximum antidepressant effects may not occur for 30 days after therapy is begun.
After symptoms are controlled, dosage should be gradually reduced to the lowest level that will maintain relief of symptoms. If maintenance therapy is necessary, the manufacturers recommend 50-100 mg of amitriptyline hydrochloride daily; however, 25-40 mg daily may be sufficient for some patients. During maintenance therapy, the total daily dosage may be administered as a single daily dose, preferably at bedtime. The manufacturers recommend that maintenance therapy be continued for at least 3 months to prevent relapse. To avoid the possibility of precipitating withdrawal symptoms, amitriptyline should not be terminated abruptly in patients who have received a high dosage for prolonged periods.
When amitriptyline is used in conjunction with a phenothiazine, commercially available fixed-ratio combination preparations should not be used initially. Dosage should first be adjusted by administering each drug separately. If it is determined that the optimum maintenance dosage corresponds to the ratio in a commercial combination, such a preparation may be used. However, whenever dosage adjustment is necessary, the drugs should be administered separately.