Side effects: are they friend or foe?

How do the specialist knowledge and skills of a prescribing pharmacist differ from those of a doctor? When justifying pharmacist prescribing, the impact on patients’ quality of care needs to be demonstrated. This is not always easy, but it can be done.

In my current role, I join medical colleagues on daily ward rounds. This close working relationship means that patients with complex pharmaceutical issues are referred to me for review.

Recently, an 85-year-old woman was admitted to the medical admissions unit with worsening general lethargy. She had a past medical history of osteoporosis and recently diagnosed depression and, on admission, was hyponatraemic (which would have been contributing to her tiredness). She was unsure of her current medication but told me she had started taking a new medicine recently.

During the ward round, no medical cause could be determined for the patient’s low sodium level so I agreed to investigate any possible pharmacological causes and initiate an appropriate management plan. I telephoned her GP surgery and was told that citalopram 20mg daily had been started 10 days earlier.

Selective serotonin reuptake inhibitors are well documented as a cause of hyponatraemia — which usually occurs within the first month of treatment. I discontinued her citalopram and restricted her fluid intake. Her sodium was normal again four days later.

All antidepressants lower sodium levels — to varying degrees — but this patient needed to receive treatment for her depression. From talking to her I discovered she was experiencing a reduced appetite and was having difficulty sleeping at night.

I started treatment with mirtazapine without delay because it has a relatively low risk of causing hyponatraemia, can stimulate appetite and can aid sleep (if taken at night). I was also confident that the citalopram could be stopped abruptly because the patient had only been taking it for 10 days.

In this case, I used my knowledge of medicines to ensure the patient received prompt and effective treatment. My understanding of the pharmacology and side effect profiles of antidepressants (and how to change from one antidepressant to another) was key.

 

David Gibson is senior clinical pharmacist (medical admissions) at Darlington Memorial Hospital