Penicillin as a toxin
According to the Material Saftely Data Sheet (MSDS) on Penicillin G:
Mouse LD50 6257 mg/kg
Rat LD50 8900 mg/kg
Rabbit LD50 5848 mg/kg
Mouse LD50 6257 mg/kg
Rat LD50 8900 mg/kg
Rabbit LD50 5848 mg/kg
No MSDS information could be found on humans. When given high doses of penicillin, the toxic effects do not actually come from penicillin itself. They come from the potassium given with the drug. Positive potassium ions end up being more toxic than penicillin, especially in renal failure patients who are unable to clear the potassium effectively. Most adverse effects of penicillin are due to an allergy.
As an allergen
Penicillin is the most commonly reported patient allergy.
However, a research study done in 2001 stated that only 10-20% of patients reporting an allergy to penicillin actually had an actual allergy to penicillin. The researchers tested this by placing penicillin on a patient's skin and looking for local signs of an allergy. Most patients showed none. They stated that "virtually all patients with a negative skin test result can take penicillin without serious sequelae." Despite this, most physicians tend to err on the side of caution; if a patient reports a penicillin allergy, they prescribe different antibiotics.
However, a research study done in 2001 stated that only 10-20% of patients reporting an allergy to penicillin actually had an actual allergy to penicillin. The researchers tested this by placing penicillin on a patient's skin and looking for local signs of an allergy. Most patients showed none. They stated that "virtually all patients with a negative skin test result can take penicillin without serious sequelae." Despite this, most physicians tend to err on the side of caution; if a patient reports a penicillin allergy, they prescribe different antibiotics.
Adverse drug effects
1% of patients using penicillin drugs have adverse drug reactions, including:
Diarrhea
Hypersensitivity
Nausea
Rash
Neurotoxicity
Urticaria
Superinfections
Less than 1% (0.1-1%) of patients using penicillin have these side effects:
Fever
Vomiting
Erythema
Dermatitis
Angioedema
Seizures (though usually in people already diagnosed with epilepsy)
Pseudomembranous colitis
Diarrhea
Hypersensitivity
Nausea
Rash
Neurotoxicity
Urticaria
Superinfections
Less than 1% (0.1-1%) of patients using penicillin have these side effects:
Fever
Vomiting
Erythema
Dermatitis
Angioedema
Seizures (though usually in people already diagnosed with epilepsy)
Pseudomembranous colitis
Image 1 source: http://images.wisegeek.com/brown-rat.jpg
Penicillin MSDS <http://www.pfizer.com/files/products/material_safety_data/150.pdf>
Mendez, D. "Penicillin Side Effects and Toxic Effects." Knjoi. <http://drugs-pharmaceuticals.knoji.com/penicillin-side-effects-and-toxic-effects/>
Salkind, A.R., Cuddy, P.G., Foxworth, J.W. "Is This Patient Allergic to Penicillin? An Evidence-Based Analysis of the LIkelyhood of a Penicillin Allergy." JAMA. 2001.
<http://jama.jamanetwork.com/article.aspx?articleid=193846>
Penicillin MSDS <http://www.pfizer.com/files/products/material_safety_data/150.pdf>
Mendez, D. "Penicillin Side Effects and Toxic Effects." Knjoi. <http://drugs-pharmaceuticals.knoji.com/penicillin-side-effects-and-toxic-effects/>
Salkind, A.R., Cuddy, P.G., Foxworth, J.W. "Is This Patient Allergic to Penicillin? An Evidence-Based Analysis of the LIkelyhood of a Penicillin Allergy." JAMA. 2001.
<http://jama.jamanetwork.com/article.aspx?articleid=193846>