TCAs and related, venlafaxine and mirtazapine

Question 1

1) Outline the MoA of TCAs

2) List 4 TCAs

Answer 1

1) Inhibit neuronal reuptake of 5-HT and noradrenaline from the synaptic cleft
2) Amitriptyline, Imipramine, Nortriptyline, lofepramine , clomipramine

Question 2

what are the common indications for TCAs? (2)

Answer 2

1) As second-line treatment for moderate-to-severe depression where (SSRIs) are ineffective.
2) Neuropathic pain

Question 3

List some of the side effects caused by TCAs

Answer 3

1) Blockade of antimuscarinic receptors causes dry mouth, constipation, urinary retention and blurred vision
2) Sedation and hypotension
3) Cardiac adverse effects include arrhythmias and ECG changes (prolongation of the QT and QRS )
4) Serious effects include convulsions, hallucinations and mania.
5) Breast changes and sexual dysfunction and rarely causes extrapyramidal symptoms (tremor and dyskinesia)

Question 4

How can side effects be reduced with the use of TCAs?

Answer 4

The risk of side-effects is reduced by titrating slowly to the minimum effective dose (every 2–3 days). Consider using a lower starting dose in elderly patients

Question 5

Outline the signs and symptoms of a TCA overdose

Answer 5

1) Hypotension, hypothermia
2) Arrhythmias
3) Convulsions
4) Coma and respiratory failure
5) Dry mouth
6) Dilated pupils and urinary retention also occur

Question 6

Caution is required when TCAs are prescribed to patients at heightened risk of adverse effects. Outline which patients TCAs should be used in caution

Answer 6

1) Elderly patients
2) Epilepsy
3) Cardiovascular disease
4) Prostatic hypertrophy
5) Glaucoma
6) Prone to constipation, may have their condition worsened by the drugs’ antimuscarinic effects.

Question 7

Outline some of the important side effects with regards to TCAs

Answer 7

1) Avoid with MAOIs as both drug classes increase 5-HT and noradrenaline levels and together they can precipitate hypertension and hyperthermia or serotonin syndrome
2) Can potentiate antimuscarinic, sedative or hypotensive adverse effects of other drugs

Question 8

Elderly patients are particularly susceptible to many of the side-effects of tricyclic antidepressants so low initial doses should be used. What should be monitored in particular in this patient group?

Answer 8

psychiatric and cardiac side-effects

Question 9

what are the monitoring requirements for TCAs (2)

Answer 9

monitor cardiac and hepatic function during long-term use

Question 10

why should limited quantities of tricyclic antidepressants be prescribed at any one time?

Answer 10

Their cardiovascular and epileptogenic effects are dangerous in overdosage

Question 11

what patient and carer advice should be provided to those taking TCAs?

Answer 11

1) Driving and skilled tasks
2) Effects of alcohol enhanced
3) Avoid abrupt withdrawal