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Caffeine and Lidocaine

Aug 7, 2011 | By Linda Tarr Kent
Caffeine and Lidocaine
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Caffeine and lidocaine both have been studied as metabolic probes to test liver function in people with early or intermediate liver disease. Caffeine also is used as a stimulant to combat drowsiness and to enhance pain medication. Lidocaine also is used as an anesthetic drug. Both sometimes are found as adulterants in illicit drugs. Consult a doctor about using either of these drugs, especially if you have heart problems.

Testing

Caffeine and lidocaine are of use as metabolic probes because both are metabolized primarily by cytochrome P-450 in your liver. Medical providers can measure metabolites, or substances formed in your liver as the drugs are broken down, in your urine or use a breath test to determine how well you are metabolizing a substance, according to "Hepatoxicity," by Hyman J. Zimmerman. Blood and saliva tests also may be used. The value of such tests, however, is limited, according to a 2004 study in the "Clinical Journal of Pharmacology."

Effect

Both caffeine and lidocaine are exclusively meatabolized by your liver. Lidocaine may work better than caffeine for assessing liver function, however, according to "Clinical Hepatology," by Henryk Dancygier. The first metabolite formed while lidocaine is metabolized is MEGX. Its concentration in saliva accurately correlates with its concentration in the blood. A saliva test is easy and noninvasive compared to other types of tests. Also, compared to caffeine clearance tests, the MEGX test is quicker and easier to perform. Testing for MEGX also has fewer variable factors than caffeine. For example, caffeine clearance decreases with age and nicotine consumption. A significant decrease of MEGX formation in your liver translates to a poor prognosis, notes Dancygier.

Adulterants

Caffeine and lidocaine also are both among the adulterants added to cocaine to increase its weight, according to "Treatment for Stimulant Use Disorders," by Richard A. Rawson and Rose M. Urban. These are used because they are similar tasting and similar acting, the authors note.

Caffeine

Caffeine's cytochrome P-450 subtype is CYP1A2. (Caffeine is a central nervous system stimulant that makes you feel more alert. It can also make you jittery, raise your heart rate, cause uneven heart rhythms, raise blood pressure, cause dizziness, cause headaches and dehydrate you. Caffeine is found in food, in over-the-counter drugs and in prescription medications. It's added to medicines to improve the effect of pain relievers or to treat drowsiness. Caffeine may cause a physical dependence or addiction, according to the U.S. Food and Drug Administration.

Lidocaine

Lidocaine's cytochrome P-450 subtype is CYP3A3/4. Lidocaine is used most often as a local anesthetic. It may be injected or applied topically. Possible adverse effects may include euphoria, light-headedness, apprehension, nervousness, dizziness, confusion, drowsiness, blurred or double vision, tinnitus, vomiting, twitching, tremors or sensations of heat, cold or numbness. High levels may cause unconsciousness, convulsions and respiratory depression and arrest. If they occur, excitatory manifestations are likely to be brief and mild. If you have liver dysfunction, the side effects are likely to be more pronounced. Side effect risk also is higher if you have pulmonary disease or congestive heart failure, according to the American Pain Society.

Contraindications

Caffeine is contraindicated, meaning you shouldn't use it, if you have a heart problem or have anxiety problems or panic attacks. Lidocaine also is contraindicated if you have cardiovascular instability. Lidocaine is contraindicated if you use alpha agonists or beta blockers and if you are allergic to other amide local anesthetics, such as bupivacaine, as well.

References

Article reviewed by William H Last updated on: Aug 7, 2011

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