How Phenobarbital Acts in Your System
Phenobarbital can be administered as an injection, a liquid elixir, or tablets. Each has their own speed of taking effect and appropriate dosages. Tablets or elixirs begin to act in about 60 minutes, and their duration lasts for 10 to 12 hours, depending on the dosage and individual metabolism. Phenobarbital is metabolized by the liver and excreted in the urine. It can be detected in the urine for up to 15 days after a dose. If you take a urine drug screen while on phenobarbital, it will likely test positive for barbiturates. Phenobarbital can interact with many prescription and nonprescription medications, supplements, and herbal products while it is in your system. It is important to talk to your doctor about all of your medications to avoid these interactions, including ones you might start or stop taking. Some drugs of special concern with phenobarbital include blood thinners, Antabuse, Vibramycin, Fulvicin, hormone replacement therapy (HRT), monoamine oxidase (MAO) inhibitors, oral steroids, sedatives, sleeping pills, tranquilizers, and medications for anxiety, depression, pain, asthma, colds, and allergies, and some medications for seizures like phenytoin (Dilantin) and valproate (Depakene). Don’t drink alcohol while phenobarbital is in your system as it can worsen side effects. Phenobarbital can harm a fetus, so it shouldn’t be used if you plan to become pregnant, and it shouldn’t be used if you are breastfeeding. Birth control pills and other hormonal contraceptives may be less effective when you are taking phenobarbital, and you may need to use a different form of birth control.
Take Phenobarbital Only as Prescribed
One reason to know how long phenobarbital remains in your system is that it is addictive which means taking larger doses, taking it more often, or taking it longer than prescribed could increase the risk of addiction.
Don’t Stop Taking Phenobarbital Suddenly
Also, do not stop taking phenobarbital suddenly without consulting your healthcare provider. Stopping suddenly can cause you to experience withdrawal symptoms which can include:
AnxietyMuscle twitchingUncontrollable shaking of a part of the bodyWeaknessDizzinessChanges in visionNauseaVomitingSeizuresConfusionDifficulty falling asleep or staying asleepFainting
If you wish to stop taking phenobarbital, your doctor will probably gradually decrease your dosage.
Overdose
Symptoms of phenobarbital overdose include heart failure, low blood pressure, weak pulse, uncontrollable movements of the eyes, loss of coordination, drowsiness, slowed breathing, confusion, delirium, headache, sleepiness, coma, large blisters, and in rare cases, death. If you think someone has had a phenobarbital overdose, call the poison control helpline at 1-800-222-1222. If the person has collapsed or is not breathing, call 911 immediately.
