What the label lists and what reports show
Phenobarbital side effects
Phenobarbital's FDA label lists its adverse reactions in its own words. FAERS holds 402 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is epilepsy (27 reports).
- No generic listed
- A presentation discontinued
- DEA Schedule IV
Check it at the source: the phenobarbital FDA label on DailyMed (effective August 27, 2026); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe following adverse reactions have been reported: CNS Depression – Residual sedation or “hangover”, drowsiness, lethargy, and vertigo. Emotional disturbances and phobias may be accentuated. In some persons, barbiturates such as phenobarbital repeatedly produce excitement rather than depression, and the patient may appear to be inebriated. Irritability and hyperactivity can occur in children. Like other nonanalgesic hypnotic drugs, barbiturates such as phenobarbital, when given in the presence of pain, may cause restlessness, excitement, and even delirium. Rarely, the use of barbiturates results in localized or diffuse myalgic, neuralgic, or arthritic pain, especially in psychoneurotic patients with insomnia. The pain may appear in paroxysms, is most intense in the early morning hours, and is most frequently located in the region of the neck, shoulder girdle, and upper limbs. …
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
This table is printed in the SEZABY label published by Sun Pharmaceutical Industries, Inc. of December 23, 2025; the label quoted above does not print one.
| Reaction | Phenobarbital (N = 32)* % | Levetiracetam (N = 19) % |
|---|---|---|
| Respiration abnormal | 25 | 5 |
| Sedation | 16 | 5 |
| Feeding disorder | 16 | 5 |
| Hypotension | 16 | 0 |
| Bradycardia | 3 | 0 |
| Hyponatremia | 3 | 0 |
| Sepsis | 3 | 0 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
Source: FDA drug label, Chartwell RX, LLC, effective August 27, 2026 (SPL set 74428144-fb24-40a5-a670-3b876e2d116c), via openFDA; the full label on DailyMed
What do FAERS reports show?
402 reports list phenobarbital among the medicines taken, each a report of something that happened, not proof the medicine caused it; 61 are coded as a death and 210 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 17 reactions below, 2 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Phenobarbital: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions