Studies have shown an increasing use of herbal medicines alongside conventional drugs by patients in their disease management especially for chronic diseases, with the attendant risks of herb-drug interactions.
In addition, 50 per cent of diabetic patients visiting healthcare facilities in Nigeria routinely manage their diabetes or other existing diseases with herbal medicines alongside prescription drugs.
Even more worrying is the frequent use of unlabeled herbal preparations which would constitute a huge challenge in the proper identification of herb-drug interactions when they occur.
In order to forestall this, adequate information about the herbal medicines and how these would, in turn, affect the effectiveness of the co-administered drug is required.
Such a co-administration can increase or decrease the blood glucose level which may be beneficial or detrimental to the health of the diabetics. This interaction may mar the management of blood glucose in diabetic patients.
A number of these herbal medicines have been identified as having overlapping interactions with prescription drugs. Now, in a new study, researchers found that Picralima nitida extract, a commonly taken herb by patients with diabetes, enhanced the blood sugar lowering effect of the oral anti-diabetics, metformin and glimepiride.
More than 400 plants have been traditionally used for the treatment of diabetes, including aloe vera leaf, bitter lemon, prickly pear, garlic, avocado pear and bitter kola.
Based on tests carried out in diabetic albino rats, these findings suggest that the co-administration of Picralima nitida with anti-diabetic drugs may pose both positive and negative clinical implication depending on their dosage.
Picralima nitida is commonly called pile plant. In Nigeria, its name differs according to tribes, for instance, the Igbos calls it Osuigwe or Abiri, Yorubas: Erin, and Idoma: Otosi.
Its various plant parts such as the leaves, seeds, stem bark and roots are used by herbalists for treatment of fever, diabetes, hypertension, jaundice, gastrointestinal disorders and malaria.
In Southern Nigeria, for instance, it is either soaked in water, palm wine or in spirits with other herbs in the treatment of malaria, body pains and diabetes.
Some diabetics in the tropics may use the seeds of Picralima concurrently with conventional antidiabetic drugs either to treat diabetes or other diseases without knowing about its possible interaction with conventional oral anti-diabetic drugs.
Moreover, researchers had found that Picralima nitida at a dose of 300mg/kg to 1000mg/kg was able to exhibit blood glucose reduction that is comparable to anti-diabetic drugs like metformin and glimepiride.
In 2016, Ugwu, Jane Ogochukwu, in a dissertation submitted to the University of Nigeria, Nsukka investigate the effect of Picralima nitida seed extract on the blood glucose reduction activities of metformin and glimepiride and the effect of Picralima nitida, metformin and glimepiride combinations on liver and blood cells using diabetic albino rat model.
They found that the co-administration of Picralima nitida with anti-diabetic drugs may have clinical implications depending on their dosage.
In the first phase of the experiment, high dose of Picralima nitida alone showed significant glucose reduction activity comparable to the high dose of glimepiride 0.4mg/kg and metformin 100mg/kg.
Low dose Picralima nitida 250mg/kg also produced blood glucose reduction that is greater than glimepiride 0.2mg/kg and 50mg metformin.
In phase two, Picralima nitida 500mg/kg significantly enhanced the glucose reduction effect of both metformin and glimepiride irrespective of their doses.
This study demonstrated that both the low and high dose Picralima nitida influenced metformin and glimepiride, the blood glucose lowering effect of metformin was potentiated when co-administered with Picralima nitida, the onset of action of both combinations was enhanced.
On the other hand, co-administration of Picralima nitida with glimepiride potentiated the effect of glimepiride, though, the effect was reduced and delayed onset action was seen in the presence of Picralima nitida 250mg.
However, this combined effects of Picralima nitida and metformin correlated with the synergistic hypoglycaemic (blood sugar lowering) effects of metformin and extract of the bitter leaf.
In addition, the results of the combined treatment with Picralima nitida and Metformin may cause a reduction in the daily dose of metformin for those patients who could be taking the seeds.
Examples of improved blood sugar control have been shown with the co-administration of Momordica charantia (bitter melon) with chlopropramide, with suggestions of a dose reduction for the latter.
When extracts of pawpaw leaves known for its hypoglycaemic effects were co-administered with glimepiride, rather than the expected enhanced hypoglycaemic effect, the leaves decreased the hypoglycaemic effect of the glimepiride, while it produced an enhanced hypoglycaemic effect with metformin.
Similarly, the water-soluble fractions of okro significantly decreased the absorption of metformin resulting in a loss of its hypoglycaemic effect under laboratory conditions.
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