Uniretic (Moexipril Hydrochloride / Hydrochlorothiazide) - Drug Interactions, Contraindications, Overdosage

DRUG INTERACTIONS

Potassium Supplements and Potassium-Sparing Diuretics: As noted above (Serum Electrolyte Imbalances), the net effect of uniretic® may be to elevate a patient's serum potassium, to reduce it, or to leave it unchanged. Potassium-sparing diuretics (spironolactone, amiloride, triamterene) or potassium supplements can increase the risk of hyperkalemia. If concomitant use of such agents is indicated, they should be given with caution, and the patient's serum potassium should be monitored.

Oral Anticoagulants: Interaction studies with warfarin failed to identify any clinically important effect of moexipril monotherapy on the serum concentrations of the anticoagulant or on its anticoagulant effect.

Lithium: Increased serum lithium levels and symptoms of lithium toxicity have been reported in patients receiving ACE inhibitors during therapy with lithium. Because renal clearance of lithium is reduced by thiazides, the risk of lithium toxicity is presumably raised further when, as in therapy with uniretic®, a thiazide diuretic is coadministered with the ACE inhibitor. These drugs should be coadministered with caution, and frequent monitoring of serum lithium levels is recommended.

Alcohol, Barbiturates, or Narcotics: Potentiation of orthostatic hypotension may occur in patients on thiazide diuretic therapy with concomitant use of alcohol, barbiturates, or narcotics.

Antidiabetic Agents: Use of thiazide diuretics concomitantly with antidiabetic agents (oral agents and insulin) may require dosage adjustment of the antidiabetic agent. Moexipril has been used in clinical trials concomitantly with oral hypoglycemic agents and there was no evidence of any clinically important adverse interactions.

Cholestyramine and Colestipol Resins: Absorption of hydrochlorothiazide is impaired in the presence of anionic exchange resins. Single doses of either cholestyramine or colestipol resins bind the hydrochlorothiazide and reduce its absorption from the gastrointestinal tract by up to 85% and 43%, respectively.

Corticosteroids, ACTH: Use of thiazide diuretics concomitantly with corticosteroids or ACTH may intensify electrolyte depletion, particularly hypokalemia.

Pressor Amines: Thiazide diuretics may decrease arterial responsiveness to pressor amines (e.g. norepinephrine), but not enough to preclude effectiveness of the pressor agent for therapeutic use.

Skeletal Muscle Relaxants, Nondepolarizing: Thiazide diuretics may increase the responsiveness to tubocurarine.

Non-steroidal Anti-inflammatory Drugs: In some patients, the administration of a non-steroidal anti-inflammatory agent can reduce the diuretic, natriuretic, and antihypertensive effects of loop, potassium-sparing and thiazide diuretics. Thus, when uniretic® and non-steroidal anti-inflammatory agents are used concomitantly, the patient should be observed closely to determine if the desired effect of the diuretic is obtained.

Other Agents: No clinically important pharmacokinetic interactions occurred when moexipril was administered concomitantly with digoxin or cimetidine.

Moexipril has been used in clinical trials concomitantly with calcium-channel-blocking agents, diuretics, H₂ blockers, digoxin, and cholesterol-lowering agents. There was no evidence of clinically important adverse interactions. In general, ACE inhibitors have less than additive effects with beta-adrenergic blockers, presumably because both work by inhibiting the renin-angiotensin system.

Coadministration of propantheline or guanabenz increased the absorption of hydrochlorothiazide.

OVERDOSAGE

No specific information is available on the treatment of overdosage with uniretic®. Treatment should be symptomatic and supportive. Therapy with uniretic® should be discontinued and the patient observed closely. Suggested measures include induction of emesis and/or gastric lavage and correction of dehydration, electrolyte imbalance and hypotension by established procedures.

Single oral doses of 2 g/kg moexipril were associated with significant lethality in mice. Rats, however, tolerated single oral doses of up to 3 g/kg. The oral LD₅₀ of hydrochlorothiazide is greater than 10 g/kg in mice and rats. For the combination of moexipril hydrochloride and hydrochlorothiazide (ratio 7.5:12.5), the approximate LD₅₀ was around 10 g/kg for mice and above 10 g/kg for rats. Addition of hydrochlorothiazide to moexipril hydrochloride did not increase the acute toxicity due to moexipril hydrochloride.

Human overdoses of moexipril have not been reported. In case reports of overdoses with other ACE inhibitors, hypotension has been the principal adverse effect noted. The most common signs and symptoms observed with an overdose of hydrochlorothiazide have been those of dehydration and electrolyte depletion (hypokalemia, hypochloremia, hyponatremia). If digitalis has also been administered, hypokalemia may accentuate cardiac arrhythmias.

No data are available to suggest that physiological maneuvers (e.g., maneuvers to change the pH of the urine) would accelerate elimination of moexipril and its metabolites. The dialyzability of moexipril is not known.

Angiotensin II could presumably serve as a specific antagonist-antidote in the setting of moexipril overdose, but angiotensin II is essentially unavailable outside of research facilities. Because the hypotensive effect of moexipril is achieved through vasodilation and effective hypovolemia, it is reasonable to treat moexipril overdose by infusion of normal saline solution. In addition, renal function and serum potassium should be monitored.

CONTRAINDICATIONS

uniretic® is contraindicated in patients who are hypersensitive to any component of this product and in patients with a history of angioedema related to previous treatment with an ACE inhibitor. Because of the hydrochlorothiazide component, this product is contraindicated in patients with anuria or hypersensitivity to other sulfonamide-derived drugs. Hypersensitivity reactions are more likely to occur in patients with a history of allergy or bronchial asthma.