Pharmacodynamic interactions

 Pharmacodynamic interactions

drug interaction is defined as an increase or decrease in the therapeutic effect of a certain drug caused by another drug, food, or supplement(May & Schindler, 2016). Drugs interact through certain mechanisms. These can include

· Pharmacokinetic interactions – influence absorption, distribution, metabolism, or excretion and increase or decrease plasma levels of a drug

· Pharmacodynamic interactions – alter the pharmacologic effect of a drug while not affecting drug plasma levels (Takeda et al., 2017).

These interactions were common with patients in the diabetic outpatient education clinic that I worked in. Many patients with diabetes suffer from comorbidities, which require treatment with multiple medications (May & Schindler, 2016). While additional medications may decrease the risk for other problems, such as heart disease, there is a higher risk of drug interactions and adverse drug effects. Metformin is the preferred medication for first-line therapy in diabetes, but the elimination rate is determined by renal function and many diabetics have some sort of kidney disease (Hsu et al., 2018). Therefore, it is essential to use caution when drugs that affect renal function are being taken at the same time.

Patient

One particular patient in the clinic followed this path. His medical history consisted of Type II diabetes, hypertension, COPD, GERD, and gastroparesis. His medications were metformin 1500 mg, Prevacid, reglan, amlodopine, and metoprolol. He also took several herbal supplements, such as Ginko Biloba, ginseng, flaxseed, and fish oil. After approximately six months of attending the clinic, he was diagnosed with kidney disease.

Pharmacokinetics

Drugs can affect pharmacokinetics by affecting absorption “due to changes in the subcutaneous adipose blood flow, muscle blood flow, and gastric emptying”(Dostalek et al., 2012, para. 1). With the patient’s stomach issues and delayed gastric emptying, there could be an altering of his gastric PH, which could affect the absorption rate of medication. Food intake and herbal supplements play a role in affecting the plasma concentration of many drugs (May & Schindler, 2016). Herbal supplements can also “interact with pharmacological medications in a different and unpredictable manner” (May & Schindler, 2016, para. 7).

Pharmacodynamics

Pharmacodynamics is the “study of biochemical and physiologic effects of drugs on the body and the molecular mechanisms by which those effects are produced (Rosenthal, Laura & Burchum, Jacqueline, 2020, p. 22). It is essential to control issues, such as high blood pressure and renal disease, while also controlling blood sugars. In order to do this, a combination of anti-diabetic medications may be used. When adding additional medications, hypoglycemia, weight gain, and fluid retention may occur so monitoring the patient is crucial (May & Schindler, 2016).

There are also many pharmacodynamic interactions of herbal supplements that can increase or decrease blood sugars(May & Schindler, 2016).

Plan of Care

When the patient initially began coming to the clinic, his A1C was 14% and his blood pressure was extremely high. He was adding herbal supplements to “help him feel better.” To ensure positive outcomes, it is important to “establish a medication education plan, monitor positive and negative patient responses, identify and address issues of nonadherence, and manage the patient’s complete medication regimen”(Rosenthal, Laura & Burchum, Jacqueline, 2020, p. 8). Education was provided regarding his disease process, his medications, and the pharmacodynamics of herbal supplements with other medications.  He discontinued the Ginko Biloba and ginseng but continued the fish oil and flaxseed because his HDL cholesterol was low at 32 mg/dl. Due to the fact that this patient did not have insurance and medication costs were a factor, metformin 1500 mg was continued. Lisinopril was added to help protect his kidneys. Once he began to show signs of kidney disease, the metformin was decreased to 500 mg and an SGLT2 inhibitor (Jardiance) was added through a patient assistance program. SGLT2 inhibitors work by preventing the kidneys from reabsorbing glucose back into the blood(SGLT2 Inhibitors (Gliflozins), 2019). Due to the fact that metformin can accumulate in the kidneys with chronic kidney disease, the patient was monitored closely for lactic acidosis. He received lab work every three months and his kidney functions, blood sugars, and blood pressure was monitored closely. Education was provided on a weekly basis and patient assistance was provided for medication and PCP appointments to ensure his compliance.

Conclusion

When providing a medication education plan and monitoring the patient’s response, while addressing issues, positive outcomes can be achieved and adverse drug reactions can be minimized. This particular patient attended the clinic weekly for education and within the first year, had decreased his A1C to 7.4%.

 

 

 

 

 

 

References

Dostalek, M., Akhlaghi, F., & Puzanovova, M. (2012). Effect of diabetes mellitus on pharmacokinetic and pharmacodynamic properties of drugs. Clinical Pharmacokinetics51(8), 481–99.  https://doi.org/10.2165/11631900-000000000-00000