The recommended adult dosage for diphenhydramine hydrochloride is 25 to 50 milligrams three to four times daily, according to Drugs.com. To use diphenhydramine as a sleep aide, 50 milligrams is the recommended dose. However, patients should visit their doctors for individualized dosing as this drug absorbs rapidly into the system.
Signs of diphenhydramine overdose include dry mouth, fixed dilated pupils, flushing and gastrointestinal symptoms, as reported by Drugs.com. If these symptoms appear, the patient should contact a health care professional immediately. The health care professional may advise the patient to induce vomiting. If so, the patient should drink a glass of water or milk and then force himself to gag. Diphenhydramine hydrochloride should not be taken with alcohol, hypnotics, sedatives, tranquilizers or any other central nervous system depressants.