Prescription concentration

This chapter provides evidence on competition between rival drugs in the UK and Spain, and shows the number of pharmaceuticals on the market, the position of dominance occupied by products in relation to their substitutes, and the prescription concentration at various levels of therapeutic and generic differentiation. 

Third, we study the degree of prescription concentration in each market. We show the prescription concentration using the Herfindahl-Hirschman index (H). The statistic //is the sum of the squares of the market shares of each product j included in group g of active ingredients, products or presentations P, as defined above. The following expression gives the definition of the Herfindahl-Hirschman index ... 

Table 4.4 shows the market share of the most frequently prescribed chemical substance in England and Spain and the H index for prescription concentration in public health care. 

The market share of the most frequently prescribed active ingredient is very small both in England and in Spain, and the prescription concentration at the level of therapeutic substances is also very low. These data paint a picture of fierce competition in markets of drugs containing different active ingredients. However, we need to study the market structure and therapeutic competition at a lower level of therapeutic aggregation in order to be able to evaluate the extent to which pharmaceuticals enjoy dominant positions in their respective groups of therapeutic substitutes. 

Table 4.7 provides some statistics on the prescription concentration of various substances at chapter, section and paragraph/subparagraph level. 

Therapeutic competition H index of prescription concentration between various therapeutic substances (%)... 

Table 4.12 provides some descriptive statistics on the prescription concentration of products containing the same therapeutic substance. 

Finally, Table 4.13 shows the number of different presentations of the same product in terms of pharmaceutical form, concentration of the therapeutic substance and size of package. The differences between countries are very small. Nevertheless, in England there appears to be a larger number of varieties per product. The weighted average of different preparations stands at two in Spain as opposed to three in England. However, these differences are not significant in terms of prescription concentration. 

Phenylephrine is seldom given systemically but is still commonly used as a mydriatic for both diagnostic and therapeutic purposes. Ocular application of phenylephrine 10% in pledget form is used to produce hemostasis in laser-assisted in-situ keratomileusis (LASIK) surgery and other ophthalmic surgical procedures. Phenylephrine is in some countries available in a non-prescription concentration of 0.12% for use as an ocular decongestant. Phenylephrine (up to 10 mg intramuscularly) has similar properties and uses to other alpha-adrenoceptor agonists. 

The holistic thermodynamic approach based on material (charge, concentration and electron) balances is a firm and valuable tool for a choice of the best a priori conditions of chemical analyses performed in electrolytic systems. Such an approach has been already presented in a series of papers issued in recent years, see [1-4] and references cited therein. In this communication, the approach will be exemplified with electrolytic systems, with special emphasis put on the complex systems where all particular types (acid-base, redox, complexation and precipitation) of chemical equilibria occur in parallel and/or sequentially. All attainable physicochemical knowledge can be involved in calculations and none simplifying assumptions are needed. All analytical prescriptions can be followed. The approach enables all possible (from thermodynamic viewpoint) reactions to be included and all effects resulting from activation barrier(s) and incomplete set of equilibrium data presumed can be tested. The problems involved are presented on some examples of analytical systems considered lately, concerning potentiometric titrations in complex titrand + titrant systems. All calculations were done with use of iterative computer programs MATLAB and DELPHI. 

Crl, Grr, A r and A r are the potential parameters of the constituents A and B of the alloy, S r r r, is the structure matrix in the most localized representation, tir are local site-occupation variables which randomly takes value 1 or 0 according to whether the site is occupied by an atom of type A or not, with probabilities proportional to the concentrations of the constituents. According to the prescription of the augmented space formalism, the effective non-random Hamiltonian H in augmented space is then... 

An increased hydrogen ion concentration, that is a considerably greater amount of acid than the theoretical two equivalents of Scheme 2-1, is necessary in the diazotization of weakly basic amines. The classic example of this is the preparation of 4-nitrobenzenediazonium ions 4-nitroaniline is dissolved in hot 5-10 m HC1 to convert it into the anilinium ion and the solution is either cooled quickly or poured onto ice. In this way the anilinium chloride is precipitated before hydrolysis to the base can occur. On immediate addition of nitrite, smooth diazotization can be obtained. The diazonium salt solution formed should be practically clear and should not become cloudy on standing in the dark. Some practice is necessary, and details can be found in the books emphasizing preparative aspects (Fierz-David and Blangey, 1952 Saunders and Allen, 1985 in Houben-Weyl, Vol. E 16a, Part II, the chapter written by Engel, 1990). These books give a series of detailed prescriptions for specific examples and a useful review of the principal variations of the methods of diazotization. Such reviews have also been written by Putter (1965) and Schank (1975). 

This product is also only available by prescription. The recommended treatment period is up to 24 weeks (McNeil Consumer Products 1997). Using the inhaler by puffing 80 deep inhalations over 20 minutes results in a systemic absorption through the buccal mucosa of 2 mg of nicotine, with maximal nicotine concentrations occurring 15 minutes after the end of inhalation. When the product is used as directed, the patient will likely use 6-16 inhalers per day. This form of NRT is relatively contraindicated in patients with asthma because, although most of the nicotine is absorbed through the buccal mucosa and it is not delivered to the lungs (McNeil Consumer Products 1997), nicotine by inhalation may produce bronchial constriction. 

In the United States, concentrations range from 2% (over-the-coimter) to 4% (by prescription). Higher concentrations can be compounded by pharmacists for stubborn cases of hyperpigmentation. Multiple studies have doc-lunented the efficacy of hydroquinone formulations [44]. 

Because the severity of symptoms and the absolute serum concentration are poorly correlated in some patients, institution of therapy should be dictated by the clinical scenario. All patients with hypercalcemia should be treated with aggressive rehydration normal saline at 200 to 300 mL/hour is a routine initial fluid prescription. For patients with mild hypocalcemia, hydration alone may provide adequate therapy. The moderate and severe forms of hypercalcemia are more likely to have significant manifestations and require prompt initiation of additional therapy. These patients may present with anorexia, confusion, and/or cardiac manifestations (bradycardia and arrhythmias with ECG changes). Total calcium concentrations greater than 13 mg/dL (3.25 mmol/L) are particularly worrisome, as these levels can unexpectedly precipitate acute renal failure, ventricular arrhythmias, and sudden death. 

It is available with or without a prescription and remains the most commonly purchased over-the-counter topical treatment for acne.12 Benzoyl peroxide is available in concentrations ranging from 1% to 10% in various formulations including creams, lotions, gels, and facial washes. 

Stuer et al. [46] evaluated the presence of the 25 most used pharmaceuticals in the primary health sector in Denmark (e.g., paracetamol, acetyl salicylic acid, diazepam, and ibuprofen). They compared PECs with experimental determinations and they conclude that measured concentrations were in general within a factor of 2-5 of PECs. Carballa et al. [45] also determined PECs for pharmaceuticals (17), musk fragrances (2) and hormones (2) in sewage sludge matrix. For that purpose they used three different approaches (1) extrapolation of the per capita use in Europe to the number of Spanish inhabitants for musk fragrances (2) annual prescription items multiplied by the average daily dose for pharmaceuticals and (3) excretion rates of different groups of population for hormones. They indicated that these PECs fitted with the measured values for half of them (carbamazepine, diazepam, ibuprofen, naproxen, diclofenac, sulfamethoxazole, roxithromycin, erythromycin, and 17a-ethiny I e strad iol). 

Finally, the weighted averages of the concentration indices are lower than the medians of these indices. For example, the median of the concentration indices at paragraph level is 62 per cent in England, whereas the weighted average is 43 per cent. Therefore, prescription is more concentrated in the majority of therapeutic markets than in a small number of high-turnover markets. 

Lovaza (omega-3-acid ethyl esters) is a prescription form of concentrated fish oil EPA 465 mg and docosahexaenoic acid 375 mg. The daily dose is 4 g/day, which can be taken as four 1-g capsules once daily or two 1-g capsules twice daily. This product lowers triglycerides by 14% to 30% and raises HDL by about 10%. 

C-ll, C-lll, C-IV, controlled substance schedule 2, 3, and 4, respectively cap, capsule chew tab, chewable tablet CINV, chemotherapy-induced nausea and vomiting liquid, oral syrup, concentrate, or suspension OTC, nonprescription Rx, prescription supp, rectal suppository tab, tablet. 

A prescription requires 0.015 mL of a drug concentrate. Using a pipet with markings from one to ten in units of 1 mL and a 100-mL graduated cylinder, explain how you would obtain the required quantity of drug concentrate Use water as a diluent. 

The source of polymixin B sulfate is a vial containing 50,000 units of the dry powder. The directions on the vial state Add diluent 9.4 mL (for a) concentration of solution 5000 units per mL. Using water for injection as the diluent, explain how you would obtain the drug needed in compounding the prescription. 

Nicotine nasal spray is marketed as a pharmacy-only medication in the UK, and is available only by prescription in the USA. The nasal spray was designed to deliver doses of nicotine to the smoker more rapidly than other NRT products. The device is a multidose bottle with a pump that delivers 0.5 mg of nicotine per 50-pL squirt. Each dose consists of two squirts, one to each nostril. Nicotine from the nasal spray is absorbed into the blood more rapidly than from the gum (Schneider et al. 1996). Venous plasma concentrations after a single 1-mg dose range between 5 and 12 ng mL Time to peak plasma concentration (7j ax) with nasal administration is around 11-13 min for 1-mg doses. This rise time is slower than for cigarette delivery (Henningfield et al. 1993), but faster than for the other NRT products. 

Phenytoin has a long half-life, 18-24 hours, after oral administration (G9), which may be prolonged further at high dosages (VI). Twice daily prescriptions of phenytoin should result in relatively constant blood concentrations once steady-state conditions have been achieved, a process taking 6-15 days (K21). A limited amount of experimental data supports this prediction (B30, Cl, D5, Hll). 

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