DEAR DR. ROACH: Your recent column regarding cognitive decline after surgery suggested careful consideration prior to elective surgery. Does this advice apply to screening colonoscopies? Since for it’s done for screening and there is no indication of any problem, does the risk outweigh the benefits for a patient 65 or older? — K.B.

ANSWER: The risk of cognitive decline after colonoscopy is very low. I could not find any data suggesting a significant risk of long-term (more than a day or two) changes to thinking or memory from the sedation or the procedure.

The sedation used for colonoscopy is very different from general anesthesia used for many surgeries. While some anesthetic agents may have greater risk for cognitive decline than others, the risk for the sedatives in colonoscopy appears to be very small.

There are risks to a screening colonoscopy. The most serious is a perforation of the colon, but bleeding and infection are other, rare risks. The preparation can cause imbalances in the salt levels of the blood. The risk of a serious complication after colonoscopy is less than 3 per 1,000 people. The benefits of early detection of colon cancer greatly outweigh the risks of a complication for nearly all healthy people between 50 and 75, and there are some recommendations to start earlier (at 45) or continue screening even older.

DEAR DR. ROACH: I am a 78-year-old woman. How can I get rid of the constant pain from the neuropathy caused from the shingles that I had four months ago? It is constant, sometimes feeling like menstrual cramps, but I also have intermittent stabs that feel like an ice pick stabbing in my pelvis. I have heard that it can last a year or even a lifetime. I was prescribed gabapentin at 100 mg, three times a day and 33 ml medical marijuana drops under my tongue twice a day for some relief, but I wish I knew that there could be an end to this. — A.C.S.

ANSWER: Shingles, caused by the recurrence of the chickenpox virus, damages the nerves (the general term for damaged nerves is “neuropathy”), and in some people causes an extremely painful sensation. It is usually described as burning, but it may have other qualities such as you are describing.

It’s much better to prevent shingles than to treat, as the treatments are only partially effective. The older a person is, the greater the likelihood of neuropathy (this particular type of neuropathy is called post-herpetic neuralgia) and the longer it tends to last.

Gabapentin (Neurontin) is a commonly used treatment for painful post-herpetic neuralgia, but I often see people using far less gabapentin than is effective. In the trial that got gabapentin indicated for PHN, the goal was to get trial subjects to a dose of 1,200 mg three times daily. My experience is that gabapentin starts to become effective in most at a dose of 300 mg three times daily, and most people can tolerate 900 mg three times daily if the dose is raised slowly enough, over months. Side effects of sedation limit the usefulness of gabapentin. Pregabalin (Lyrica) is easier to titrate to an effective dose, but it’s expensive. Older drugs, such as amitriptyline, may also be effective. A pain management specialist has expertise in treating PHN.

Cannabis-based medications are slightly better than placebo in treating chronic neuropathic pain. A recent review found that 21% of people had significant pain relief with cannabis-based medicines, compared with 17% using placebo. However, 61% noted nervous system adverse effects, compared with 29% of placebo. Psychiatric disorders occurred in 17% of the cannabis group and 5% of the placebo group.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected] or send mail to 628 Virginia Dr., Orlando, FL 32803.

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