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What the label lists and what reports show

Penicillin g side effects

Penicillin g's FDA label lists its adverse reactions in its own words. FAERS holds 3,439 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 drug hypersensitivity (1,180 reports).

  • Generic listed

Check it at the source: the penicillin g FDA label on DailyMed (effective September 16, 2020, Sandoz Inc); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions

Body as a whole The Jarisch-Herxheimer reaction is a systemic reaction, that may occur after the initiation of penicillin therapy in patients with syphilis or other spirochetal infections (i.e., Lyme disease and Relapsing fever). The reaction begins one to two hours after initiation of therapy and disappears within 12 to 24 hours. It is characterized by fever, chills, myalgias, headache, exacerbation of cutaneous lesions, tachycardia, hyperventiliation, vasodilation with flushing and mild hypotension. The pathogenesis of the Herxheimer reaction may be due to the release from the spirochaete of host stable pyrogen. Hypersensitivity reactions The reported incidence of allergic reactions to all penicillins ranges from 0.7 to 10 percent in different studies (see WARNINGS ). …

Source: FDA drug label, Sandoz Inc, effective September 16, 2020 (SPL set 91950983-4884-40d1-abd8-bcc953d61b7f), via openFDA; the full label on DailyMed

What do FAERS reports show?

3,439 reports list penicillin g among the medicines taken, each a report of something that happened, not proof the medicine caused it; 271 are coded as a death and 917 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 20 reactions below, 9 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.

Reports received each year

The 25 most reported reactions

  • Drug Hypersensitivity1,180
  • Hypersensitivity (named in the label)420
  • Drug Ineffective (a use or a product term, not a reaction)397
  • Rash (named in the label)315
  • Dyspnoea295
  • Diarrhoea251
  • Off Label Use (a use or a product term, not a reaction)236
  • Nausea (named in the label)234
  • Malaise (named in the label)215
  • Drug Intolerance214
  • Abdominal Pain Upper194
  • Anxiety175
  • Headache (named in the label)172
  • Cough171
  • Condition Aggravated (a use or a product term, not a reaction)166
  • Urticaria (named in the label)166
  • Arthralgia (named in the label)164
  • Pruritus (named in the label)157
  • Fatigue156
  • Hypertension156
  • Pain154
  • Vomiting (named in the label)142
  • Pneumonia (a use or a product term, not a reaction)139
  • Pyrexia129
  • Therapeutic Product Effect Decreased (a use or a product term, not a reaction)120

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Penicillin g: the full record
label, generics, price, shortages, recalls
Side effects hub
the most reported medicines and reactions