Side effects and Toxicity

Question 1

Allergic reactions

Answer 1

May occur with the administration of any antimicrobial, but are most commonly associated with B-lactam drugs (penicillins and cephalosporins).
True Penicillin hypersensitivity is rare and patients with other non-allergic side effects are often wrongly classified as ‘penicillin allergic’.
Approximately 10% of truly penicillin allergic patients are also allergic to cephalosporins.

Question 2

Immediate hypersensitivity

Answer 2

Anaphylactic shock is life threatening and usually follows parenteral administration of the antibiotic.
This is IgE mediated and occurs within minutes of administration.

Question 3

Delayed hypersensitivity

Answer 3

May take hours or days to develop and can have an immune complex or cell mediated mechanism.
Drug rashes are the most common manifestation, but drug fever, serum sickness and erythema nodosum may also occur.

Question 4

Gastrointestinal side effects

Answer 4

Commonly encountered with antimicrobial usage. Nausea and vomiting are common, but diarrhoea associated with toxin production by Clostridium difficile is now a major problem in healthcare acquired infection.
C. Difficile is an anaerobic gram positive bacillus which can be carried asymptomatically in the GI tract, especially in the very young and old.
Treatment is with oral metronidazole or oral vancomycin. Patient is isolated and infection controls are put in place.

Question 5

Thrush

Answer 5

Broad spectrum antimicrobials also suppress normal flora in other parts of the body and result in the overgrowth of resistant organisms.

Question 6

Liver Toxicity

Answer 6

Important organ for metabolism and excretion, the liver is susceptible to a variety of side effects.
Varies from transient elevation of liver enxymes to a sever hepatitis.
These symptoms are most common in patients with pre-existing liver disease and in pregnancy.
Tetracycline, anti-tuberculous drugs isoniazid (INH), rifampicin and flucloaxacillin have been associated with hepatotaxicity.

Question 7

Renal Toxicity

Answer 7

Kidney is the most important route of drug excretion.

Nephrotoxicity is dose related and is more common patients with pre-existing renal disease.

Question 8

Neurological toxicity

Answer 8

Ototoxicity - Most seen following aminoglycoside or vancomycin use.
Damage to inner ear which may lead to temporary or permanent hearing loss.

Optic Neuropathy - Ethambutol ( anti TB drug) is associated with dose related optic nerve damage.
Regular monitoring of optic nerve function therapy is recommended.

Encephalopathy (Affects brain function) and convulsions -
May result from high dose penicillin and cephalosporin , or with aciclovir (anti-viral).

Peripheral neuropathy (damage to nerve function) - 
Metronidazole, nitrofurantoin, anti-tuberculous drug isoniazid may cause peripheral neuropathy.

Question 9

Haematological Toxicity

Answer 9

Antimicrobials may have a toxic effect on bone marrow resulting in selective depression of one cell line (neutropenia) or unselective depression of all bone marrow (pancytopenia).
May result in folate deficiency which leads to megaloblastic anaemia after prolonged therapy.