By L. Musan. Eastern Michigan University.
A few features of controlled-release products must be considered in therapeutic drug monitoring: 1 best suprax 200mg. When multiple doses of a controlled-release drug product are administered discount suprax 100mg with mastercard, before reaching steady state buy 200mg suprax overnight delivery, the difference between peak and trough plasma concentrations is not as great as would be evident after multiple doses of rapidly absorbed drug products (Figure 7-16) order suprax 200 mg without a prescription. Because drug may be absorbed for most of a dosing interval generic suprax 200 mg with amex, an elimination phase may not be as apparent-that is, the log of plasma drug concentration versus time curve may not be linear for any part of the dosing interval. Some predictions can be made about plasma drug concentrations with controlled-release preparations. For preparations that result in continued release of small drug doses, the plasma drug concentration can be estimated as follows: or: Clinical Correlate The peak and trough concentrations of controlled-release products generally differ very little, so plasma drug concentration sampling is generally done at the approximate midpoint of any dosing interval to approximate the average steady-state concentration. Also, if the average plasma drug concentration is estimated (determined approximately halfway through a dosing interval), drug clearance can be determined using the same formula. Finally, the effect of changing the dose or dosing interval on plasma drug concentration can be estimated. For example, if it is known from previous regimens that a patient has a theophylline half-life of 7 -1 hours (K = 0. Again, the assumption is that the bioavailability (F) is the same for each product. The considerations for controlled-release dosage forms will become increasingly important as more drugs are being formulated into preparations that can be administered at convenient intervals (daily or even less frequently). Clinical Correlate The importance of the absorption rate depends to some extent on the type of illness being treated. For example, when treating pain it is usually desirable to use an analgesic that is rapidly absorbed (i. For chronic diseases, such as hypertension, it is more desirable to have a product that results in a lower absorption rate and more consistent drug absorption over time, so that blood pressure does not change over the dosing interval. Typical plasma drug concentration versus time curve at steady state for a controlled-release oral formulation. Plasma drug concentrations over time with controlled-release and rapid-release products. If 500 mg of a drug is given orally and 250 mg is absorbed into the systemic circulation, what is F? A, C, B Use the following information for questions 7-8 through 7-10: A 500-mg oral dose of drug X is given, and the following plasma concentrations result: Plasma Concentration Time after Dose (hours) (mg/L) 0 0 4. If two formulations of the same drug are tested and product A has a faster absorption rate than product B, product A will take a shorter amount of time to reach peak concentration. The plasma concentrations and times observed for several points are as follows: Observed Plasma Time after Dose (hours) Concentration (mg/L) 3. You wish to begin a patient on a sustained- release preparation of drug Y and to maintain an average plasma drug concentration of - 1 20 mg/L. After 5 days (assume steady state has been reached), the mid-dose (average) plasma drug concentration is 13 mg/ L. What should the new daily dose be to result in an average plasma drug concentration of 25 mg/L? Finally, plot the residual concentration points on graph paper and use the first and last sets of time/ concentration pairs to calculate the slope of this line, which also represents Ka. You can see that this value differs considerably from Vextrap; Varea is usually a better estimate. Residual concentration = back-extrapolated concentration minus actual concentration. Residual concentration = back-extrapolated concentration minus actual concentration. Residual concentration = back-extrapolated concentration minus actual concentration. Residual concentration = back-extrapolated concentration minus actual concentration. Residual concentration = back-extrapolated concentration minus actual concentration. Describe the effects of variation in these two factors (Ka and F) on the concentration versus time curves. Look up the bioavailability for the three dosage forms of Lanoxin (tablet, elixir, and liquid filled capsule) and then plot representation concentration versus time curves for all three products at the same dose.
Prevention strategies that focus on positive social and behavioural development appear to be effective suprax 200mg with mastercard. Programmes that only provide drug-relevant information cheap suprax 100mg on-line, or try to boost self-esteem generic suprax 100mg online, are less likely to be effective at reducing demand cheap suprax 100 mg with amex. Taking action on preventing the underlying causes of drug use may be as effective as purchase suprax 200 mg amex, or more effective than, preventing drug use directly. Summary • Current prevention strategies aim to reduce drug use by influencing attitudes and behaviour, in order to prevent or delay the initiation of drug use. Secondary prevention interventions, such as harm-prevention strategies, are yet to receive much in the way of attention. These programmes improve young people’s knowledge about drug use, and have a small impact, notably in delaying the onset of use. Those who had taken drugs said lessons helped them understand why people take drugs and that not as many people as they thought take drugs. There is conflicting evidence about their efficacy in reducing drug use among vulnerable groups, and there is a risk that they further stigmatise already marginalised individuals. The age range 11 to 13 years has been identified as a crucial period for effective intervention. Taking action on preventing the underlying causes of drug harm rather than preventing drug harm directly may be more effective. This analysis provides a model for the components of effective medical management of drug dependence. In Chapter 9, medical responses to the use of other illicit drugs and drug-related harms are considered, while Chapter 10 examines medical management of illicit drug use within the criminal justice system. The notion of medical management of chronic disease seems more useful than episodes of care. By the time they come for treatment, many dependent drug users are socially marginalised, or in prison, lacking access to the rewards arising from employment, personal relationships and family participation. Treating heroin addiction frequently involves the social reintegration of marginalised individuals lacking in skills and having few and often tenuous social connections. Hospital admission rates for drug-specific conditions have also shown a strong positive association with deprivation. Drugs, especially illicit drugs, are viewed with fear and disapproval (see Sections 2. The stigma associated with addiction is a significant barrier in providing healthcare to people misusing drugs, as negative attitudes – on the part of both practitioners and patients – can compromise effective care (see Sections 2. Stigma may have a public health benefit, in making certain risky or harmful behaviours less attractive, and the stigma associated with illicit drugs probably discourages many people from using them. Stigma can also attract troubled young people; which probably explains why many drug prevention programmes paradoxically lead to more, rather than less, drug use. This can progress to increasing isolation, disrupted relationships with family, and loss of social supports. All these factors contribute to the development of the ‘addict identity’ – someone who has become conditioned to see himself existing outside of normal society, isolated and defiant. Once in treatment, and able to stop compulsive drug use, it is not rare for the patient to sabotage his own treatment, for example by dropping out, or missing scheduled appointments, taking refuge in the familiar experience of failure, disapproval and conflict. There is a major element of behavioural treatment in how doctors, nurses and pharmacists respond to the challenge of disaffected, impulsive behaviour. Clinics delivering the same ‘treatment’ often achieve dramatically different outcomes, and the quality of the therapeutic relationship is one factor contributing to the greater effectiveness observed in some settings. Managing addiction involves long-term support, educating patients about their condition, promoting engagement in and compliance with treatment, monitoring symptoms and dealing with complications. Practitioners treating drug-dependent patients require not just skills and knowledge, but also a positive attitude towards treatment and recovery. Negative attitudes on the part of drug-dependent patients may sabotage treatment, but so too can negative attitudes on the part of practitioners. Their theme was that, freed from the cycle of addiction and treated with respect and dignity, heroin users can develop a different image of themselves, and behave with self-respect and dignity. They emphasised that negative assumptions about drug users need to be balanced by a belief in their capacity to change, and a sense of the practitioner’s role in fostering that change. From the mid 1990s, neuroscience research has been promoted as showing that addiction is a ‘chronic relapsing brain disease’ (see Section 1. The secondary school he attended recognised that he had learning difficulties and he was sent to a boarding school for children with special needs. Within two years he was addicted to heroin, spending £150 to £200 daily on the drug, gaining the money by begging, thieving and raiding phone boxes and parking meters.