Phenobarbital dosage depends on the reason for prescribing the medication, the patient's health, and how well the patient responds to the drug. It is a potent central nervous system depressant, and doctors usually start with a low dose and slowly titer up to find the point where it will be effective for the patient, and the risk of side effects is as low as it can be. It can require several weeks to find the appropriate dosage, and it is important to take the medication as directed. Patients should avoid taking extra doses or abruptly stopping.
Doctors may prescribe phenobarbital for the treatment of seizures and insomnia. They can also use it as a sedative. Doses are usually given in milligrams; a typical adult can take between 50 and 100 milligrams per day for seizures, for example, or 30-120 to achieve a state of sedation. In cases where the drug is prescribed for animals, it is usually used for seizures, and the veterinarian may prescribe grains rather than milligrams, a different system of measurement. Patients should always ask which measuring system is being used to make sure they get the dosage right.
Older patients need a lower phenobarbital dosage because they are more sensitive to the drug. Likewise patients who have liver and kidney disease, as they are less capable of metabolizing it and could experience complications if they receive too much. For children, phenobarbital dosage also includes a weight component, as children are much smaller than adults and can run a gamut of sizes, making weight a more critical aspect of dosing to prevent overdoses.
If a patient does not respond to a low dose, the doctor can gradually increase it until the patient starts to experience relief. The end phenobarbital dosage may remain fairly stable once the patient's medical problem is under control. In some cases, patients develop a tolerance and may need to increase their dosage to get the same effect. If the medication appears to be less effective over time, patients should discuss it with their doctors.
When determining phenobarbital dosage, a doctor will consider medical history. Patients could be taking other medications that might interact and complicate the way phenobarbital works in the body. They could also be at increased risk of side effects or severe reactions on the basis of personal or family medical history, and this must be considered when making dosage decisions.