Potassium/Magnesium Supplement

The present invention relates to a combination of potassium and magnesium-salts useful in the treatment of hypokalemia and hypomagnesemia. In particular, it relates to a combination of controlled release potassium chloride and an immediately-released magnesium salt, preferably magnesium oxide.

It is well known that mineral deficiencies such as hypokalemia and hypomagnesemia can occur for a variety of dietary or physiological reasons and often result from long term therapy with drugs such as thiazides and loop diuretics. Hypokalemia and hypomagnesemia can cause variety of unpleasant or dangerous symptoms including cardiac arrhythymias, weakness, fatigue and muscle cramps.

While the need for potassium and magnesium supplementation is well recognized, no combination supplements known to date have been completely successful. Potassium is known to cause irritation and/or ulceration in the gastric tract when taken orally, so combinations of salts such as the granulation described in UK Patent 1,356,096, which provides both potassium and magnesium in immediate release form, are likely to promote gastric upset.

Other known formulations wherein the release of both the potassium and magnesium are controlled, e.g. those described in U.S. Pat. No. 4,104,370 and UK patent 1,356,097, tend to promote the same gastric problems, but for the opposite reason. That is, wax-matrix formulations such as disclosed in the cited patents may not disintegrate rapidly or completely, causing high local concentrations of potassium injurious to the gastric tract. These wax-matrix tablets, as well as other controlled release formulations such as that described in German patent 2,132,923, wherein enteric coated capsules are disclosed, (which capsules in effect become immediate release formulations when the coating and capsule dissolve, thereby presenting the problems associated with non-controlled release potassium salts) further present the possibility of reduced bioavailability of magnesium. Magnesium is absorbed from the gastrointestinal tract in the region of the upper small bowel by means of an active process closely related to the transport system for calcium. Therefore, the use of magnesium in a controlled-release or enteric-release form would be inappropriate due to the reduced biavailability. Moreover, unlike potassium, the controlled release of magnesium is unnecessary since magnesium salts are not associated with gastrointestinal irritation and ulceration.

Furthermore, the above cited patents may not provide therapeutic doses of both potassium and magnesium. The dosages in the formulation in the cited patents range from a low of 0.25 to a high of 15 meq. for magnesium and from a low of 0.4 to a high of 10 meq. for potassium. However, the recommended daily dietary allowance for magnesium in adults is 25 to 33.4 meq (milliequivalent). The daily dose of magnesium required to prevent depletion in patients receiving diuretics has not yet been established, while a daily dose of 20 meq of potassium is typically used for the prevention of hypokalmia.

We have found that a combination of controlled release potassium chloride and an immediately-released magnesium salt provides the necessary physical and pharmacological characteristics to allow maximum efficacy.

In particular, the present invention relates to a combination of coated potassium chloride crystals and a magnesium salt, wherein the potassium chloride crystals are coated with a combination of ethylcellulose and at least one of hydroxypropylcellulose and polyethyleneglycol. The coated crystals are comprised of about 60 to 86.5% by weight of potassium chloride, about 9 to 15% by weight of ethylcellulose, and about 0.5 to 3% by weight of at least one of hydroxypropylcellulose and polyethylene glycol and preferably may comprise 0.5 to 2% of a lubricating agent such as magnesium stearate or stearic acid (all percentages based on the total weight of the coated crystals). The potassium chloride crystals have a mesh size of 30-50 mesh, preferably 40 mesh. Coated potassium chloride crystals as described above are disclosed in WO 86/04817, published Aug. 28, 1986, which claims priority of co-assigned U.S. Ser. No. 702,714, filed Feb. 19, 1985, now abandoned, and herein incorporated by reference. Such coated crystals, when introduced into the gastric tract, e.g., from a quickly-disintegrating tablet, are distributed by the peristaltic motion of the gut and do not allow undesirable locally high potassium chloride concentrations.

The magnesium salt is selected from pharmaceutically acceptable salts such as magnesium hydroxide, magnesium carbonate, magnesium sulfate, magnesium chloride, magnesium gluconate, magnesium phosphate, magnesium oxide, or a combination of such salts. High magnesium content salts are preferred, e.g., the hydroxide and oxide, since the final dosage form is therefore less bulky. Magnesium oxide is a preferred salt.

The coated potassium chloride crystal and magnesium salt mixture can be filled into capsules, either a conventional pharmaceutically acceptable capsule to be swallowed whole by the patient, or a capsule which may be opened by the patient. The latter capsules or packets (e.g., sealed cellophane envelopes) may be used to administer the mixture in liquid form (e.g., suspend the mixture in water or juice) or in soft food (e.g., sprinkle the mixture on applesauce).

The mixture of coated potassium chloride crystals and magnesium salt can also be compressed into tablets for oral administration. Such tablets may comprise conventional excipients, such as diluents, compression aids, disintegrants, lubricants, flavorings and coloring agents. Tablets of the present invention preferably comprise a compression aid such as micro-crystalline cellulose or lactose; a disintegrant such as crospovidone (cross-linked polyvinylpyrrolidone), a modified starch (e.g., sodium carboxymethyl starch), or a modified cellulose gum (e.g., croscarmellose sodium type A, N.F.); and a lubricating agent such as magnesium stearate or stearic acid. Preferred are microcrystalline cellulose as the compression aid, crospovidone as the disintegrant, and magnesium stearate as the lubricant. Concentration ranges (based on total tablet weight) of the excipients are about 4-20%, preferably about 6% compression aid; about 0.5 to 10%, preferably about 1% disintegrant; and 0 to about 1%, preferably about 0.5% lubricant.

Tablets may be prepared by conventional tabletting procedures.

Dosage forms of the present invention comprise a magnesium slat in an amount to provide about 7.5 to about 35 meq elemental magnesium per day, preferably about 7.5 to about 15 meq per day. The typical daily dose of potassium for the prevention of hypokalemia is 20 meq per day, and for the treatment of potassium deficiency, 40-100 meq per day. The lower concentration dosage forms of this invention may be taken in a single daily dose, but the higher dosages are preferably administered in divided dosages taken 2 to 4 times a day. Dosage forms of this invention thus comprise about 10 meq to about 20 meq potassium chloride and 7.5 to 35 meq of magnesium salt.

The following examples show the preparation of the coated potassium chloride crystals and several typical tablet formulations.

Method of Manufacture:

The potassium chloride crystals (30-50 mesh) are coated in a 6" Wurster fluidized bed column with 15% (w/w) of Ethocel.RTM. 100 and Klucel.RTM. L.F. are dissolved in a methylene chloride and methanol co-solvent system and magnesium stearate is then added to the polymer solution to form a suspension. The suspension is stirred throughout the coating process. The potassium chloride crystals are coated at a 60.degree. inlet temperature. The spraying pressure is 1.5 bars and the spray speed is approximately 15 ml per minute.

Method of Manufacture:

Mix the ingredients thoroughly in a suitable blender for 10-15 min. and compress into suitable-sized tablets using a suitable die and punch set with a compression force in the range of 4,000 to 10,000 psi.

Prepare tablets as in Example 2.

Prepare tablets as in Example 2.