<p>Vitamin B1 does not have adverse effects when given orally, but in a few fatal cases anaphylactic reactions have occurred after intravenous administration of large doses (400 mg) in sensitive patients, especially children, and in one case following an intramuscular dose of 125 mg. The risk of such reactions increases with repeated administration of the drug by parenteral route. Transient mild soreness may occur at the site of intramuscular administration.</p>