Ferrous Sulphate Tablets 325 Mg

Ferrous Sulphate Tablets 325 mg: Interactions and Bioavailability

Interaction with Parkinson's Disease Medication (Sinemet)

Impact on Levodopa and Carbidopa Bioavailability

Ferrous sulphate tablets, commonly prescribed for iron-deficiency anemia, have been shown to significantly affect the bioavailability of medications used in Parkinson's disease treatment, particularly Sinemet, which contains levodopa and carbidopa. When ferrous sulphate (325 mg) is taken with Sinemet, there is a notable decrease in the area under the curve (AUC) for both levodopa and carbidopa. Specifically, levodopa AUC decreases by 30%, and carbidopa AUC decreases by more than 75%. This reduction in bioavailability is likely due to the formation of chemical complexes between iron and the active ingredients in Sinemet.

Clinical Significance

Despite the significant reduction in bioavailability, the average reduction in Sinemet's efficacy did not achieve statistical significance in the study, although there was a strong correlation between reduced levodopa AUC and reduced efficacy (r = 0.83). This suggests that while the interaction is clinically significant for some patients, it may not affect all patients uniformly. Further studies are needed to fully understand the clinical implications of repeated ferrous sulphate ingestion with Sinemet.

Interaction with Levodopa Alone

Chelation Mechanism

In a study involving normal subjects, the co-administration of ferrous sulphate (325 mg) with levodopa resulted in a 55% decrease in peak levodopa levels and a 51% decrease in AUC. The likely mechanism for this interaction is the chelation of iron by levodopa, where iron in its ferrous state is rapidly oxidized to the ferric state in the small intestine, binding strongly to levodopa. This interaction significantly reduces the bioavailability of levodopa, although the clinical significance of this reduction remains to be fully established.

Interaction with Gemifloxacin

Timing of Administration

The bioavailability of gemifloxacin, a fluoroquinolone antimicrobial, is also affected by ferrous sulphate. When gemifloxacin is administered three hours after ferrous sulphate, there is an 11% reduction in AUC and a 20% reduction in Cmax, which are not considered clinically significant. However, when gemifloxacin is taken two hours before ferrous sulphate, its bioavailability is not altered. These findings support the recommendation that gemifloxacin should be administered at least two hours before or three hours after ferrous sulphate to avoid significant interactions.

Interaction with Methyldopa

Effects on Absorption and Blood Pressure Control

Ferrous sulphate also affects the absorption and metabolism of methyldopa, a medication used for blood pressure control. Co-administration of ferrous sulphate (325 mg) with methyldopa results in a significant decrease in the proportion of methyldopa excreted as "free" methyldopa and an increase in the proportion excreted as methyldopa sulfate. This interaction leads to an 88% reduction in the quantity of "free" methyldopa excreted and a significant decrease in methyldopa absorption. Clinically, this interaction can result in increased blood pressure in patients on chronic methyldopa therapy, which normalizes after discontinuation of ferrous sulphate.

Conclusion

Ferrous sulphate tablets (325 mg) can significantly interact with various medications, affecting their bioavailability and clinical efficacy. These interactions are particularly notable with Parkinson's disease medications like Sinemet, levodopa alone, gemifloxacin, and methyldopa. Understanding these interactions and timing the administration of these medications appropriately can help mitigate adverse effects and ensure optimal therapeutic outcomes. Further research is needed to fully elucidate the clinical significance of these interactions and develop comprehensive guidelines for co-administration.

Summary

Not a yes or no question