Author: Sumela Chatterjee (Sister Tutor, Nsms Nursing Institute)
Published On: 28-10-2024 | 2 min Read

1.Tachy - fast, phylaxis-protection.
2. Tacyphylaxis = acute tolerance.
3.Examples- Indirectly acting sympathomimetic agents.
4. Mechanism: due to depletion of neurotransmitter (noradrenaline) from sympathetic nerve endings.

What is Tachyphylaxis?

Tachyphylaxis is a medical term describing an acute, sudden decrease in response to a drug after its administration. i.e. a rapid and short-term onset of drug tolerance. It can occur after an initial dose or after a series of small doses. Increasing the dose of the drug may be able to restore the original response.

Tachyphylaxis is the continued or repeated exposure to a drug that may lead to a weakened pharmacological response. This presumed to be a consequence of diminished receptor sensitivity in response to consistent stimulation by a drug agonist, which produces a diminished pharmacological response in consequence. This is distinct from tolerance. This desensitization process can be a consequence of a decrease in the number of receptors or attenuation of the response because the drug has promoted neurotransmitter release in excess of presynaptic production. The presence of certain enzymes can limit cyclic AMP-based signalling, disrupt second messenger systems, and diminish the availability of receptors at the cell membrane .

Characteristics:

1. Quick onset of tolerance.

2. Decreased response with repeated doses.

3. Eventual loss of effectiveness.

Causes:

1. Receptor desensitization.

2. Feedback mechanisms.

3. Metabolic adaptations.

4. Pharmacokinetic changes.

Drugs That Can Cause Tachyphylaxis

• Antidepressants and SSRIs
• Nitrates for chest pain
•  Hydralazine for blood pressure
• Visine AC eye drops
• Albuterol asthma inhalers
•  Ranitidine for acid reflux
•  Some local anesthetics
•  Oxymetazoline nasal spray
• Erythromycin for gastroparesis
•  Hormone replacement therapy
•  Viagra for erectile dysfunction

 

Consequences:

1. Dose escalation.

2. Treatment failure.

3. Increased side effects.

4. Dependence or addiction.

 

Management strategies:

 

1. Dose adjustment.

2. Drug rotation.

3. Combination therapy.

Tachyphylaxis is an important consideration in medical treatment, as it can impact the effectiveness of medications and require adjustments to treatment plans.