Learning in Outpatient Pharmacy

Introduction

A few years ago, a senior pharmacist described outpatient pharmacy as a "dark hole" where most newly registered pharmacists are placed. However, it can be a valuable place to build a foundation in pharmacy practice.

In outpatient pharmacy, we receive prescriptions from various clinics within the hospital, including general medical, surgical, ophthalmology, dermatology, rheumatology, paediatrics, neurology, nephrology and more.

  • To properly screen prescriptions within a short time frame, we must be familiar with indications, usual dosages, maximum dosages, off-label uses and contraindications of all medications.

Additionally, these factors should also be taken into consideration.

NOTE: Life in the outpatient pharmacy teaches you with what minimum amount of information you will be comfortable when making a decision.



Familiarity with Drugs and Their Dosage

My colleague asked a provisional registered pharmacist, do you know the correct dosing of albendazole tablet for a 3-year-old child.

  • The provisional registered pharmacist shook his head.
  • I frowned because the provisional registered pharmacist has just filled the albendazole prescription and coincidentally, doctor prescribed a wrong dose.
  • This raises up a thought in my mind: Has the overwhelming outpatient workload made some of us to stop learning and checking when unsure?
  • It worries me a lot, because we have been taught that safeguarding patients from potential harms is pharmacists' top priority.

Gone were the days that we need to carry heavy textbooks around.

Whenever I encounter unfamiliar drugs or dosing (especially those high doses, such as lamotrigine 200 mg BD), I will crosscheck with the reference at hands.

  • Pharmacists should be at least confident that the medications that we supply would not harm the patients.
  • Remember, even though most prescriptions are free of medication errors, pharmacists need to stay vigilant at all times.

Also, through encountering numerous prescriptions on a daily basis, you will gradually become familiar with brand names and develop a sense of common and inappropriate dosages for medications.

  • For instance, when you come across a prescription for gliclazide modified release tablets at a dosage of 120 mg twice daily, you will immediately recognize that it exceeds the maximum allowed dosage (120 mg once daily).
  • Additionally, in the cases of HAART patients, you may encounter situations where the raltegravir dose needs to be doubled to 800 mg twice daily when used concurrently with rifampicin as part of tuberculosis regimen in adult patients due to drug interactions.



Simple Assessment

When patients come to us to replace old inhalers, I often review their previous dispensing record. Occasionally, I encounter patients who exchange MDI salbutamol inhalers too frequently, prompting further investigation.

  • Each new MDI salbutamol contains 200 doses. If a patient finishes an inhaler within a month, they are using an average of 6 to 7 puffs per day. Isn't that alarming?
  • According to GINA, if a patient uses reliever therapy more than twice a week, their asthma is likely only partially controlled or uncontrolled.

Similarly, if a patient has not come for medication refills in a long time, there should be concerns on medication compliance.

  • Are they adhering to their treatment?
  • Have they been obtaining medications from elsewhere?
  • Have they been recently admitted to ward?

As an outpatient pharmacist, I have encountered several cases of patients taking medications at incorrect doses or frequencies and complaining that their medications finished before the scheduled pharmacy appointment date.



Renal Dose Adjustment

If a patient with end-stage renal function (ESRF) is recently started on metformin, we should contact the doctor and intervene regarding the potential risks of lactic acidosis.

  • Unlike in a ward setting, we are unable to calculate creatine clearance and suggest renal dose adjustments.
  • However, it is common to see some prescriptions marked to indicate that the patient is having chronic kidney disease.

NOTE: Metformin should also be avoided in severe hepatic impairment.

Can you name a few medications that require renal dose adjustment and those that do not?

  • Vildagliptin 50 mg once daily when CrCl <60 ml/min (usual dosing is twice daily).
  • Trimetazidine 20 mg BD when CrCl <60 ml/min and contraindicated when CrCl <30 ml/min (usual dosing is three times daily).
  • NSAIDs should be avoided in CKD patients.
  • Amoxicillin and clavulanate 625 mg is dosed once daily when CrCl <10 ml/min.



Off-Label Use

In Ministry of Health settings, we are required to submit KPK applications for medications used for off-label indications.

When a certain dosing is commonly prescribed at our facility, we may not question it further upon encounter.

  • However, it is important to keep in mind that certain commonly prescribed doses may be off-label, exceeding the maximum recommended doses by the manufacturers, such as felodipine 10 mg twice daily.

Last month, we received a prescription from the geriatric clinic for donepezil 20 mg tablet once daily.

  • At first glance, the dose exceeds the maximum dose stated in the product leaflet (10 mg once daily), so we decided to double-confirm with the prescriber.
  • However, upon checking Lexicomp or Medscape, for moderate to severe Alzheimer disease, donepezil may be increased further to 23 mg once daily if stable on 10 mg for ≥3 months. Doses of 23 mg/day may be associated with a limited increase in efficacy compared to 10 mg/day and with increased adverse effects.

Another interesting example is when ophthalmologists prescribe Simbrinza ophthalmic suspension as 1 drop 3 times daily in affected eyes (even though the approved dosing in the Malaysian product leaflet is twice a day).

  • The three-times-daily dosing can be found in Lexicomp.



Clinical Management

At my hospital, more elderly patients are prescribed with donepezil compared to memantine. What could be a possible explanation for this prescribing pattern when both medications are indicated for Alzheimer disease?

As suggested in British National Formulary,

  • In patients with mild-to-moderate Alzheimer's disease, monotherapy with donepezil HCl, galantamine or rivastigmine are first line treatment options.
  • If acetylcholinesterase inhibitors are not tolerated or contraindicated, memantine HCl is a suitable alternative in patients with moderate Alzheimer's disease.
  • Memantine hydrochloride is the drug of choice in patients with severe Alzheimer's disease.

Moreover, you may also notice many Parkinson's disease patients also have constipation issue. This can be attributed to several factors.

  • Sedentary lifestyle due to reduced mobility.
  • Difficulty chewing and swallowing can lead to decreased food intake, particularly fruits and vegetables which are rich in fibre.
  • Dopamine deficiency in the brain can impair muscle control.
  • Certain medications used for Parkinson's, particularly anticholinergics, can have a constipating side effect by further slowing down bowel movements.

Have you ever wondered why ivabradine is prescribed to heart failure patients? What is the scientific evidence behind the prescribing? What is the reason behind starting some patients on isosorbide mononitrate? Or how about medication options for ADHD?

In addition to what you have learned during clinical rotations, you can also apply that knowledge in the outpatient pharmacy setting.

  • For example, if a post N-STEMI patient stops taking their statin medication, there is a high likelihood that it was just an omission error. In such cases, it is necessary to phone the prescriber for intervention.

Always justify medication prescribing based on the patient's clinical condition!

  • Should a patient be prescribed with Lomotil tablets for constipation?



Polypharmacy

A few days ago, a patient approaches us with a query about why he was not no longer receiving pyridoxine 10 mg tablets.

  • This patient is currently in the maintenance phase of tuberculosis treatment.
  • His current prescription medications include metformin 500 mg twice daily, atorvastatin 20 mg at night, Akurit 2, 4 tablets once daily and Neurobion 1 tablet once daily.

Pyridoxine is often prescribed to prevent peripheral neuropathy associated with isoniazid therapy for Mycobacterium tuberculosis. The recommended dose can range from 10 mg to 50 mg daily.

Given this information, what is your decision?

If you carefully review the patient's medication list, you will notice that he is already taking Neurobion. Each Neurobion tablet contains

  • 100 mg Vitamin B1 (thiamine disulphide)
  • 200 mg Vitamin B6 (pyridoxine hydrochloride)
  • 200 mcg Vitamin B12 (cyanocobalamin)

Therefore, once the patient started taking Neurobion, the separate pyridoxine 10 mg tablet can be discontinued.

Similarly, in practice, you may come across polypharmacy cases where a patient is prescribed simvastatin at one clinic, but atorvastatin at another clinic.

  • These cases may require medical intervention to address the discrepancy.

NOTE:

  • Neurobion can be beneficial in cases of vitamin B12 deficiency anaemia.
  • The maximum recommended dose for Neurobion is up to 1 tablet 3 times a day. However, long-term megadoses of pyridoxine over 250 mg/day are associated with cases of peripheral neuropathy, so they are not advisable.
  • Folic acid is actually vitamin B9.



Dermatological Examination

As we know, physical examination is crucial in dermatological complaints.

  • If your facility has a dermatology clinic, you can ask patients to show the affected skin area when dispensing topical preparations.
  • Moreover, this experience will be useful if you ever venture into community pharmacy later on.



Summary

After working in outpatient pharmacy for several years, many may find the daily tasks of filling and dispensing prescriptions repetitive and never ending.

  • Hopefully, this post encourages you to continue learning while working in the outpatient pharmacy.

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