Mean effective dose

Restless leys syndrome (RLS) PO 0.5 mg once daily at bedtime, slowlytitrate up until symptoms resolve or drug intolerance limits further adjustment. Mean effective dose is 2 mg/day and ranges from 1-4 mg/day. 

Females of the desert spider Agenelopsis aperta emit a volatile pheromone that attracts conspecihc males (Riechert and Singer, 1995). This pheromone was identified as 8-methyl-2-nonanone (1 Fig. 4.1), a previously unknown arthropod semio-chemical. It was found by headspace analysis and abdominal washings of females 2 weeks after their hnal molt, when they become sexually receptive it was absent in females of other age classes. The pheromone attracted males in a three-choice arena system at doses as low as 500 ng (Papke et al., 2001). Another female-specific ketone, 6-methyl-3-heptanone (2), was not attractive. Very low doses of 1 (10-9 mg/ml applied to a hlter paper placed in empty juvenile female webs) also induced courtship behavior in males (Papke et al., 2001). The normal behavioral sequence was followed, except for phases which required input from the female. The ED50 value (mean effective dose) of 1 was 5.5x 10-4 mg/ml hexane. In contrast, ketone 2 only induced a response in some males at unnaturally high concentrations... 

The ED50 is the mean effective dose of a drug necessary to produce a therapeutic effect in 50 per cent of the test sample. 

Figure 11.1 Illustration of the Dixon up-down method. Patients are treated in order of randomization, and the size of each test dose is determined by the response of the previous patient. In this example, patients who do not respond (O) are followed by a patient treated at the next higher dose size vice versa, patients who do respond ( ) are followed by a patient treated at the next lower dose. When the line has changed direction at least six times, the mean effective dose is about the ECjo (in this case, 5 u, broken line). There are many, often more sophisticated, variants of this basic technique...

Two sets of C-arm CT scan parameters and effective dose are presented below for Artis zee systems (Siemens AG, Healthcare Sector, Forchheim, Germany). They include mean effective dose values for the head and Hver regions determined using a normal-size, male Alderson phantom with embedded TLDs. Since effective dose depends on phantom positioning and size, however, measurement outcomes may vary. This is why great care was taken to position the phantom identically for all experiments to obtain comparable results. 

This trend is obviously ongoing. It corresponds to the development and spreading of new powerful MSCT systems that allow new types of investigations due to their fast acquisition modes. In Germany, for example, the frequency of CT examinations has increased from about four percent of all X-ray examinations in 1997 to about six percent in 2003 (e.g., Brix et al. 2005 Bundesamt fur Strahlenschutz 2006 Regulla et al. 2003). As a consequence, CT is currently causing more than 50% of the annual mean effective dose administered to individual members of the public due to medical X-ray procedures. 

The mean dietary intake of soy isoflavones in Asian populations consuming soy-based diets ranges from 20-40 mg isoflavones/day, with upper percentile consumer intakes of 70 mg/day (corresponding to around 1 mg/kg body weight). In the six month intervention studies in Western postmenopausal women, the effective dose for improved BMD was around 80-90 mg/day, while in the one year, randomized, double-blind, placebo controlled clinical trial, the effective dose was 54 mg/day. Overall, the dietary recommendation is to consume 50 mg isoflavones/day in combination with standard nutritional requirements for calcium and vitamin D. 

A survey of the radon concentrations in a representative sample of more than 2000 dwellings in the UK has been completed and provisional results are now available. On average, concentrations are 29% lower in bedrooms than in living areas. The mean radon concentration weighted for room occupancy is 22 Bq m 3. Assuming an equilibrium factor of 0.35 and a mean occupancy of 75%, the mean annual exposure in UK homes is assessed as 0.08 Working Level Months (WLM) and the mean annual effective dose equivalent as 0.43 mSv. 

In the radon surveys the primary quantity determined is the indoor air mean radon activity concentration. From a radiological health perspective it is the dose arising from the inhalation of radon daughters that is of interest. The conversion from radon exposure to annualised effective dose equivalent for the survey was carried out using the factors given in Table I which are similar to those being used in other European surveys. The occupancy and equilibrium factors given in this table are assumed mean values for Irish... 

Figure 7. Effective dose equivalent per hour and per unit radon concentration (AJ-B, 7 J-E) as a function of the equilibrium factor. The full lines are calculated with the mean values of the 72 measurements (Xa -. 37/h, XVent . 41/h, P -. 53, A.M.D. —. 15 lJm) and changing attachment rates.

Exposure to natural sources of radiation is unavoidable. Externally, individuals receive cosmic rays, terrestrial X-rays, and gamma radiation. Internally, naturally occurring radionuclides of Pb, Po, Bi, Ra, Rn, K, C, H, U, and Th contribute to the natural radiation dose from inhalation and ingestion. Potassium-40 is the most abundant radionuclide in foods and in all tissues. The mean effective human dose equivalent from natural radiations is 2.4 milliSieverts (mSv). This value includes the lung dose from radon daughter products and is about 20% higher than a 1982 estimate that did not take lung dose into account (Table 32.4). 

Potency is compared using the median effective concentration (EC50) or median effective dose (ED50), the meanings of which are subtly different. 

Russia remains secretive about this operation. Reporters learned that they drilled holes in the floor and used vents high on the wall to pump gas into the theater. Regrettably, however, they were unable to learn the precise nature of the gas, beyond the admission by a Russian scientist that it was a derivative of Fentanyl. Several highly potent drugs fit that definition, including carfentanil, sufentanil, alfentanil, remifentanil and etorphine. Any of these can produce anesthesia, lasting from minutes to hours. A Russian medical authority later added that they used 5x the effective dose in order to guarantee a rapid effect on the terrorists. It is not clear exactly what this means. 

As no international consensus has been achieved in the OECD/IPCS project (OECD 2003a) in order to differentiate between dose (concentration)-response (effect) relationship and because it in reality is difficult to understand the subtle differences in the different terms as defined in the OECD/IPCS project, the broader and more general definition provided in the TGD (EC 2003) will be used in this book, and will generally be referred to as dose-response. Consequently, the term dose will, in this book, generally mean both dose and exposure concentration unless otherwise stated. 

For adverse effects such as carcinogenicity, mutagenicity, and disease incidence, a hormetic effect means low-dose reduction and high-dose enhancement of response. The dose-response curve is the J-shape, see Figure 4.4. 

By ingestion, the mean lethal dose for humans probably lies between 120 and 180ml. Symptoms include burning pain in the mouth and throat, abdominal pain, nausea, vomiting, and occasionally diarrhea. Central nervous system effects are excitement, ataxia, confusion, and stupor. Convulsions may occur several hours after ingestion. Fever and tachycardia are common, and death is usually attributed to respiratory failure. ... 

B.5.3 Effective Dose Equivalent and Effective Dose Equivalent Rate. The absorbed dose is usually defined as the mean absorbed dose within an organ or tissue. This represents a simplification of the actual problem. Normally when an individual ingests or inhales a radionuclide or is exposed to external radiation that enters the body (gamma), the dose is not uniform throughout the whole body. The simplifying assumption is that the detriment will be the same whether the body is uniformly or nonuniformly irradiated. In an attempt to compare detriment from absorbed dose of a limited portion of the body with the detriment from total body dose, the ICRP (1977) has derived a concept of effective dose equivalent. 

---