Pharmacologic class (EPC) · 3 drug pages

Histone deacetylase inhibitor: adverse event reports filed with FDA

2,757 reports list a drug in this class as a suspect or interacting product, 2006–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

2,757
reports across the class: 0% of all reports; 51
reports, 12 months to June 2026: 126 in the 12 months before; 90%
marked serious by the reporter: 57.4% across all reports; 3
drugs with a page: brand and generic names counted separately

Histone deacetylase inhibitor is a pharmacologic class (an FDA Established Pharmacologic Class) with 3 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 2,757 adverse event reports received by FDA, 0% of the database, from July 2006 to June 2026.

51 reports arrived in the 12 months to June 2026, down 60% from 126 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 90% of the class's reports are marked serious, 20.1% record death among the outcomes and 49.5% record hospitalisation, as reported.

Across the class the reactions recorded most often are febrile neutropenia (10%), thrombocytopenia (7.6%) and nausea (6.6%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
Vorinostat	generic	1,441	21	97.7%	Febrile neutropenia
Romidepsin	generic	686	27	96.4%	Drug ineffective
ZolinzaVorinostat	brand	630	3	65.2%	Product use in unapproved indication

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Febrile neutropeniafever with low white blood cells10%276
Thrombocytopenialow platelets7.6%209
Nauseafeeling sick6.6%182
Anaemialow red blood cells6%165
Diarrhoealoose or frequent stools5.9%162
Fatiguetiredness5.4%148
Vomitingbeing sick4.8%132
Product use in unapproved indicationused for a purpose not on the label4.7%129
Sepsisa severe body-wide response to infection4.6%126
Pyrexiafever4.5%125
Drug ineffectivethe medicine did not work as expected4.2%116
Platelet count decreasedlow platelet count4.1%114
Neutropenialow neutrophils, a type of white blood cell4%110
Off label useused for a purpose or in a way not on the label3.8%106
Dehydrationdehydration3.7%102
Electrocardiogram QT prolongeda QT prolongation on the ECG3.7%101
Deaththe patient died; cause not stated by this term3.2%89
Disease progressionthe disease advanced3.1%86
Decreased appetitereduced appetite3%84
Pneumonialung infection3%82
Dyspnoeashortness of breath2.9%80
Malignant neoplasm progression2.4%65
Astheniaweakness or lack of energy1.9%53
White blood cell count decreasedlow white cell count1.8%51
Hypotensionlow blood pressure1.8%50

Solid bar: share of all class reports. Hollow bar: the median share across the 3 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death20.1%554

Life-threatening12.8%352

Hospitalisation (initial or prolonged)49.5%1,365

Disability2.6%73

Congenital anomaly0%0

Other serious42.4%1,169

Not serious10%277

Patient age

Under 22.6%71

2 to 114.7%129

12 to 173.1%85

18 to 448.3%229

45 to 6425.7%708

65 to 7416.1%445

75 and over9.7%268

Age not given29.8%822

Who reported

Physician30%828

Pharmacist4%111

Other health professional44.4%1,223

Lawyer0%0

Consumer or non-health professional14.6%402

Not given7%193

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Histone deacetylase inhibitor reports

Which drugs are in the Histone deacetylase inhibitor class on this site?

Vorinostat, Romidepsin and Zolinza. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

2,757 reports through June 2026, 51 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

febrile neutropenia (10%), thrombocytopenia (7.6%), nausea (6.6%), anaemia (6%) and diarrhoea (5.9%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.