Mrs. GM is an 83 yo female patient measuring 5ft 5in and weighing 140 lbs. She is presenting to your community pharmacy today with a new prescription for Fosamax 70 mg PO once weekly. Other current medications include omeprazole 40 mg PO daily (for GERD), Tylenol arthritis pain 650 mg PO prn q8h, calcium 1200 mg daily, and ergocalciferol 50000 IU PO once weekly. Her most recent labs are Na 135 mEQ/L, K 3.7 mEQ/L, and SCr of 0.9 mg/dL. She states the doctor told her this new medication was because of her moderate risk for developing a fracture but did not give her any more information. Which statements are true about Fosamax? Select all that apply.

A. Fosamax works by stimulating osteoblastic activity which promotes bone formation

B. She should take this medication first thing in the morning and wait at least 30 minutes before eating and remain upright for at least 30 minutes

C. If this oral formulation is not tolerated, there is an IV formulation of Fosamax available for administration

D. She should take this medication with a full glass (6-8 oz) of water

E. Use of Fosamax should not be administered to our patient due to renal insufficiency

Answers with rationale: 

The correct answers are B and D.

Alendronate, aka Fosamax, is a bisphosphonate which work by inhibiting osteoclast activity and promote osteoclast apoptosis. Anabolic agents such as abaloparatide and teriparatide work by stimulating osteoblastic activity, making choice A incorrect. Choice B is correct because these steps are taken to reduce esophageal irritation and increase the absorption of Fosamax. Choice C is incorrect. While other IV bisphosphonates are available for use (e.g. zoledronic acid), Fosamax is only available orally.  Choice D is correct because only 6-8 ounces of plain water should be taken with alendronate. Just like food consumption and laying down after taking alendronate, other beverages besides plain water can increase esophageal irritation and reduce absorption. Finally, choice E is incorrect because alendronate is only contraindicated in CrCl < 35 mL/min. The patient’s creatinine clearance is 43 mL/min, and below is how to calculate it.

Actual body weight=140 lbs.÷2.2 lbs/kg=63.6 kg
IBW=45.5+2.3(5)=57 kg
Since Actual/ideal body weight ratio is < 1.2, will use ideal body weight
CrCl=(140-age)(weight in kg))/(72 X SCr)  X 0.85 if female
CrCl=(140-83)(57))/(72 X 0.9)  X 0.85 = 42.6 mL/min

Naplex competency areas covered

2.1 – Pharmacology, mechanism of action, or therapeutic class

2.2 – Commercial availability; prescription or non-prescription status; brand, generic, or biosimilar names; physical descriptions; or how supplied

3.6 – Drug contraindications, allergies, or precautions

4.1 – Perform calculations based on patient parameters or laboratory measures

5.5 – Instructions or techniques for drug administration

 References

1. Abrahamsen B, Eiken P, Eastell R. Proton pump inhibitor use and the antifracture efficacy of alendronate. Arch Intern Med. 2011 Jun 13;171(11):998-1004. doi: 10.1001/archinternmed.2011.20. Epub 2011 Feb 14. PMID: 21321287.

I would like to personally thank everyone for their kind words this past year as this will be the last question of 2021. But don't worry as we will be back in 2022 with more questions of the week! Our first two posts of 2022 will be dedicated to preparing a plan for your success on the NAPLEX.  

I also would like to thank three of my UGA College of Pharmacy students for their incredible work in helping me prepare these questions each week: Logan Bradley, Ryan Bok, and Alexandria Parrish.