MMA Consortium

Alkahmzatton increases the solubility of the methotrexate in the unite but also increases its excretion.

Clinical evidence, mechanism, importance and management
Methotrexate is much more soluble in alkaline than in acid fluids For this reason urinary alkalinizers (and ample fluids) have been given to patients on high dose methotrexate therapy to prevent the precipitation of methotrexate in the kidney tubules which would cause damage However alkahnization also increases the loss of methotrexate in the urine because at high pH values more of the drug exists m the ionized form which is not readily reabsorbed by the tubules This increased loss was clearly shown in a very large number of patients (69-75) in whom alkahnization of the urine (pH 7 + ) with sodium bicarbonate and hydration reduced the serum methotrexate concentrations at 24 h by 40% at 48 h by 73% and at 72 h by 77%. In this instance the interaction was being exploited therapeutically to avoid toxicity This interaction has also been shown by others. Its possible consequences should be recognized if concurrent use is undertaken.

More about Methotrexate: www.methotrexate.co.uk.