How does medication know where exactly the pain in my body is?

When you miss a step and fall, resulting in excruciating pain in your knee… you take a painkiller. When you accidentally cut your finger while making dinner… you take a painkiller. When you have an inexplicable headache… you take a painkiller. How do these pain killers seem to work in all of these areas of the body? How does the medication know where the pain is? Pharmacology, a branch of medicine that focuses on studying the uses, effects and mechanisms of action of drugs, helps in providing answers to such questions.

So, here goes… When you swallow a painkiller, it dissolves in the stomach or sometimes the small intestines before it is absorbed into the whole body. Pills are not smart enough to only travel to the place where their action is required. However, the secret to the function of painkillers depends on the mechanism with which pain is mediated in the human body.

When one is injured, cells release molecules called prostaglandins, and nerve endings are sensitive to these prostaglandins. Following prostaglandin release, nerves then transmit signals to the brain communicate the intensity and site of the pain. It would make sense then to reduce the synthesis of prostaglandins to stop transmission of the pain signals, right? This is exactly how pain relievers like aspirin work. They are distributed throughout the body, and reduce prostaglandin synthesis, reducing the transmission of pain signals.

Therefore, a painkiller does not know where the pain actually is, but it works by reducing prostaglandin synthesis in areas where there high levels of production of these chemical mediators of pain, resulting in relief.

However, since the drug travels throughout the whole body, it could potentially work where it is not supposed to, and this unfortunately results in side effects. Regarding pain reduction, prostaglandins are not only released in injured cells, but specific types of prostaglandins are constantly produced by the body for the maintenance of normal bodily functions. As shown in the figure below.

Reduction of the prostaglandins needed for normal bodily functions leads to various side effects. For example, the use of pain killers may result in the loss of prostaglandins needed for protection of the stomach, leading to stomach ulcers. Fortunately, prior to the use of drugs, clinical trials are typically conducted to investigate that any side effects are not detrimental to life.

The phenomenon of how drugs work is not only limited to painkillers. Although many drugs are distributed throughout the body, their main action is based on correcting the abnormalities that occur in the biology of various diseases. For example, many anti-cancer drugs work by targeting cells that grow at a fast rate. Though the medication will kill the fast-growing cancer cells, it will also result in the loss of healthy cells that grow fast, like hair follicles, leading to side effects like hair loss. Therefore, when taking any type of medication, one should keep in mind that the distribution of drugs in the body could result in undesired side effects, and overuse of over-the-counter medications should thus be avoided.

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Blue skies and burnt trees

The Cape is a special place to do just about anything; surfing, whale watching, brewing, foresting and field tripping. On the 19th of August, I set off on a 3800 km journey to and around the Southern and Eastern Cape with one of FABI’s extension officers, Sandisiwe Jali, and two graduate students, Bianca Jardim and Sydney Sithole. The purpose of this field trip was to collect insect specimens and investigate various pest and disease issues in commercial forestry plantations. It isn’t often that the Tree Protection Co-operative Programme (TPCP) finds itself in the Cape, when compared to the much closer Limpopo, Mpumalanga and KwaZulu-Natal provinces, which made this trip quite distinctive.

Field trips around South Africa are always memorable; you get to see more of this beautiful country, you get to interact more closely with other students, meet the people in the forestry industry, and put your finger on the pulse of plant health in SA. Our first stop was to Stellenbosch, wine country, to meet Deon Malherbe, a researcher at Stellenbosch University. Deon is monitoring a Eucalyptus (gum) trial, which was setup by Camcore–an international tree breeding organization–to look at the performance of various hybrids across different sites. This valuable trial is under attack by a number of Eucalyptus pests, which we helped Deon identify. Together, we worked out a scoring system for better assessing the damage caused by these insects.

From there, we set off east to Riversdale, about 50 km north of Still Bay, to collect a few pine logs containing the larvae of a woodwasp, Sirex noctilio. The larvae and adults of this wasp will be examined at FABI for the presence of a tiny worm, Deladenus siricidicola—a bio-control agent developed at FABI that has saved the South African forestry industry more than 400 million rand. Here we paused to take in some of the sights while we thought about what R400 million could buy you.

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The next day, we continued east–towards Knysna–to meet Awelani Netshituka, a forester working for PG Bison at the Ruigtevlei office. Many parts of the Cape have been, and still are, at the mercy of a severe drought—the worst in 100 years. We were often reminded about using water sparingly by the little notes stuck on the walls near the taps and toilets of our accommodation. While the drought meant one couldn’t take long showers anymore, it also meant that much of the vegetation hadn’t had a good shower either. The dry conditions, high winds speeds and building fuel load led to the fires that swept through Knysna and the surrounding areas, claiming seven lives.

Awelani showed us some of the areas that had been devastated by the fires and the recovery operations under way to try and salvage some of the burnt timber. In the valley below the Ruigtevlei office, in front of thousands of dead trees, there are long lines of what looked like neatly stacked mounds of charcoal. When we asked what those lines were, we were told that they were the burnt logs they had harvested after the fire. They have harvested so much, the market is flooded. Now they have to try and store it! The arrangement of theses logs under sprinklers are called wet decks, which helps keep the wood moist until they can be used.

While many trees were harvested, the lesser-affected younger stands were left to recover. Awelani took us to some of these compartments. The prolonged drought has had a significant impact on these trees. They are trying to recover but without good rains they are being attacked by a number of different secondary or opportunistic pests and fungi, killing those too weak to put up a fight. And this wasn’t isolated to a single company or region. We saw more examples of this at a number of sites we visited.

For any industry growing plants and selling their products, climate is going to be a more important part of planning; for South Africa, a water scarce country, even more so. We are going to have to be smart with how we collect, store and recycle our water. For our plants, we are going to have to develop more efficient breeding strategies, develop and implement possible GMOs, and we are going to need more scientists to understand the effects of climate on pests and diseases because we are going to have many more blue sky days (no rain) and more burnt trees (any crop plant, really) if we don’t.