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Tachyphylaxis is a medical phenomenon where the response to a repeatedly administered drug progressively diminishes, leading to a decrease in effectiveness of the drug. This can occur with a variety of drugs and can lead to the need for increased dosages to achieve the same effect.

Definition

Tachyphylaxis is defined as the rapid decrease in response to a drug after repeated doses over a short period of time. This is different from drug tolerance, which is a more gradual decrease in response over a longer period of time.

Mechanism

The exact mechanism of tachyphylaxis is not fully understood, but it is believed to involve changes in the receptors that the drug targets. These changes can include down-regulation of the receptors, or changes in the receptor's ability to respond to the drug.

Examples

Examples of drugs that can cause tachyphylaxis include nitroglycerin, which is used to treat angina, and nasal decongestants such as phenylephrine and oxymetazoline. Tachyphylaxis can also occur with drugs used to treat depression, such as selective serotonin reuptake inhibitors (SSRIs).

Management

Management of tachyphylaxis can be challenging. In some cases, it may be possible to switch to a different drug that works in a similar way but does not cause tachyphylaxis. In other cases, it may be necessary to increase the dosage of the drug, although this can increase the risk of side effects.

See also

• Drug tolerance
• Desensitization (medicine)
• Pharmacology

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