Pharmacology, side effects and interactions – focus on perioperative implications

Pharmacology, side effects and interactions – focus on perioperative implications

Introduction

Citalopram is a Selective Serotonin Reuptake Inhibitors (SSRI) used in the treatment of depression. This drug has some implications for the anaesthetist and perioperative practitioners, which will be briefly discussed in this article

Sudden discontinuation pre-operatively can result in ‘discontinuation syndrome’ is associated with a variety of non-specific symptoms (fatigue, ataxia, paraesthesia etc) but also psychosis, hallucinations and suicidal ideation. This is particularly important to consider if the patient is unable to take oral medication post operatively.

There are also a number of drug interactions with implications for the anaesthetist. SSRI’s have significant anti-cholinergic effects and so can interact with other drugs with similar effects. The most important risk is of precipitating serotonin syndrome when tramadol or meperidine is given in conjunction with SSRIs. In addition SSRIs may impair the metabolism of codeine to morphine (CYP2D6), meaning that the patient given codeine may not receive adequate analgesia. There is also a risk of bleeding when NSAIDs and /or warfarin and citalopram are co-ingested. The table summarises the pharmacology, common side effects and common interactions

 

  Pharmacology Interactions Side effects
C Chiral mixture Carbamazepine Concentration is poor
I Inhibits SSRU Itraconazole Increased salivation
T T1/2 is 30 hours Tryptophan Taste disturbances
A Absorption in minutes Azoles Abnormal vivid dreams
L Liver metabolism 80% Li Long QT
O Oral drops Omeprazole Ophthalmic medriasis
P Protein binding 50% Pimizoles Post SSRI sexual dysfunction*

(*VIAGRAN)

R Receptors:. 5HT2C,M1,H1 Recreation eg.MDMA Rhinitis
A Availability(bio)80% in 4hrs Antidepressants eg MAOIs Aggression
M Metabolised(desmethylcitalopram) Metoprolol Migraine,Malaise,Micturitio

*Remember”VIAGRAN

V Vaginal dryness

I   Impotence

A  Anorgasmia

G Genital anaesthesia

R  Reduced libido

A Anhedonia

N Nipple insensitivity

 

Features of (citalopram)SSRI Discontinuation syndrome:

Remember ” BEE STING”

B Brain zaps

E Exhaustion/fatigue

E Emesis/nausea

S Suicidal thoughts

T Tremours

I Insomnia

N Nightmares

G GI eg.diarrhoea

 

 

Citalopram Overdose Citalopram is similar to other SSRIs in the many toxic features it produces, although it is more cardiotoxic and associated with QT prolongation (Isbister et al,2004, Ojero-Senard et al,2017) and convulsions (MHRA 2011). Fatalities are uncommon when citalopram is taken alone in overdose. However deaths have occurred with large doses and when other drugs are co-ingested. If taken with other serotonergic agents there is a risk of serotonin toxicity Serotonin Syndrome.

Serotonin syndrome is a predictable consequence of excessive serotonergic activity at CNS and peripheral serotonin receptors. For this reason, experts strongly prefer the term ‘serotonin toxicity’ or ‘serotonin toxidrome’.Excess serotonin activity produces a spectrum of specific symptoms including cognitive, autonomic and somatic effects. The symptoms may range from barely perceptible to fatal, and include hyper reflexia and hyperthermia

 

The features of this syndrome could be remembered as ”SEROTONIN”

S Sweating

Shivering

Sedation

E Epidemiology is complex

R Renal failure

Rhabdomyolysis

O Ocular clonus

T Triggering agents: Refer to”BAD-MONSTER”

B Buspirone

A Amphetamine

D Dopamine antagonist eg.metoclopramide

M MOIs

O Opiates

N Nutrition eg.kiwis, plantain,tomato

S    SSRIs, Syrian Rue, St. John Wort

T  TCAs

E   Ecstasy

R Recreational eg.cocaine

O Ophthalmic (pupillary dilatation)

N Nausea and diarrhoea

I  Investigations: no lab tests

N Numerous DD; refer to “SWEAT”   S  Sympathomimetic intoxication

W Withdrawal of sedatives

E   Encephalitis/meningitis

A  Anticholinergic toxicity

T  Temperature 20 MH

 

In conclusion, citalopram and SSRIs are commonly used drugs, with a number of serious implications for anaesthetic practice. The mnemonics in this article will act as an important aide memoir when faced with such a patient.

Authors:

Sher Mohammad [1], M. Anser Javed [2], Amitav Sahoo [3]
1. Consultant Anaesthetist, Royal Hallamshire Hospital, Glossop Road, Sheffield
2. Consultant anaesthetist Royal Hallamshire Hospital, Sheffield.
3. Specialist registrar A/E Northern General Hospital, Sheffield

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