Understanding medicine Dose and Individual Variability in Response to medicine The dosages recommended by the Food and Drug Administration (FDA) for medications are based on extensive testing on large populations. These dosages are designed to be effective and safe for the majority of people. However, these recommended dosages are statistical averages and may not be ideal for everyone. An FDA-approved dose that works well for one person may be ineffective or unsafe for another. This variability occurs because individuals differ significantly in how they metabolize and respond to medications. Individual Variability in Medicine Response People's responses to medications are influenced by various factors, including age, weight, liver and kidney function, concurrent medications, overall health, and genetics. These factors determine how quickly a drug is broken down and excreted from the body and how well the drug interacts with protein receptors to produce desired effects. Consequently, the ideal dosage for one person may differ significantly from that of another, even if they have the same condition, underscoring the importance of personalized medicine tailored to individual characteristics. For example, an effective dose for one person might be much lower or higher than the average dose. Additionally, a dose that is effective for someone may also be unsafe, while a safe dose may be ineffective. FDA-Recommended Maximum Dosages FDA-recommended maximum dosages are determined by identifying the dose at which a certain percentage of people experience adverse effects. For instance in case of sertraline, a medicine used for OCD treatment and depression treatment, if 10 out of 100 people experience adverse reactions to a particular medication at doses above 250 mg, the FDA might set the maximum recommended dose at 250 mg. This cutoff is a risk/benefit tradeoff based on pooled data rather than individual differences. However, treating the FDA maximum as an absolute limit can result in under-treatment of depression or OCD treatment for some individuals. For example, about 12 out of 100 people who respond well to a dose between 250-300 mg may not receive adequate treatment of OCD if their dose is limited to 250 mg. While Dr Shariq Qureshi, Psychiatrist in Jaipur recognizes that FDA recommendations are not rigid rules, some less-experienced psychiatric doctors may treat them as such, leading to challenges in achieving optimal treatment for depression or bipolar in patients. Importance of Personalized Dosing The process of finding the optimal dosage for a patient with psychiatric condition, known as titration, involves starting with a lower dose of antidepressant medicine and gradually adjusting it based on the patient's response. This approach helps identify the lowest possible dose that effectively manages the condition without causing unacceptable side effects. The ideal dose might be much lower or higher than the average dose of depression medicine, depending on the individual's unique response to the depression medicines. One critical factor influencing the optimal dose is the concentration of the medicine in the blood. Some people may require higher doses because their bodies break down the medication more quickly, resulting in lower blood concentrations. Conversely, others may need lower doses due to slower breakdown, leading to higher concentrations and potentially toxic effects. Understanding these differences in metabolic rates is crucial for tailoring dosages to individual needs. Given the variability in individual responses, it is essential to start with low doses and adjust based on the patient's unique reaction to the medication. Patient Examples of Dosage Variability Consider a patient Mrs. X with a fast gastrointestinal (GI) transit time, possibly due to gastric surgery or other medical conditions. This person may require higher doses of oral medications to achieve the desired effect because the medication is excreted before it can be fully absorbed. In one case, a woman who had undergone GI surgery needed 1600 mg of quetiapine daily—twice the FDA maximum dose—to achieve the desired effect without adverse side effects. To ensure the dose was safe, Dr Shariq psychiatrist, measured the blood concentration of the medication, which fell within acceptable limits. Pediatric Dosages and Metabolism In children, dosages often need to be adjusted based on body weight, particularly for medications that are quickly excreted. However, for drugs that accumulate in the body, such as antidepressants, the rate at which the body breaks down the medication—known as the metabolic rate—becomes more important. Younger individuals generally have slower metabolic rates, meaning they may require lower doses of depression medicines to achieve the desired blood concentration. Conversely, as people age, their metabolic rates increase, necessitating higher doses to maintain therapeutic levels. Dr Shariq - Psychiatrist